Major interaction on record — check this product against your medications before combining. Check your meds →
Dietary supplement

Tang Kuei Plus Ingredients & Drug Interactions

by Herbalife

Tang Kuei Plus label
See full label image
Tablet Or Pill Category: Botanical With Nutrients
Most serious interaction: Major
Clinical methodology reviewed by · Updated Sep 16, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Tang Kuei Plus against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Major

Tang Kuei Plus is a dietary supplement by Herbalife with 3 active ingredients. Its ingredients are commonly taken for common cold and immune support, antioxidant support, skin health and collagen formation.Based on those ingredients, 985 medications have a known interaction with it, the most serious rated major. The ingredients most likely to interact are Passionflower extract, Vitamin C, Tang Kuei root extract. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

Jump to a section

Check Your Meds Against Tang Kuei Plus by Herbalife

Ask about any prescription or over-the-counter medication and we check it for interactions with Tang Kuei Plus by Herbalife — and tell you which ingredient is responsible.

Pharmacist-reviewed data Checks every ingredient Answer in seconds
Prefer a human? Send your question to our licensed pharmacists — free, answered by email within 24 hours.

HelloPharmacist Scorecard of Tang Kuei Plus by Herbalife

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Sep 17, 2026

What’s inside

Full disclosure
Ingredient Transparency · database check
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 3 of its 3 active ingredients.
  • No proprietary blends here — you can verify the dose of every single component.

Tang Kuei Plus contains three active ingredients: vitamin C, passionflower extract, and Tang Kuei root extract (also called dong quai). Vitamin C is a familiar antioxidant nutrient.

Passionflower is a traditional herbal extract used to support relaxation and sleep. Tang Kuei is a traditional Chinese root used in herbal formulations for centuries.

The tablet also contains several inactive ingredients that are standard in supplement manufacturing: microcrystalline cellulose (a binder), modified food starch, stearic acid, croscarmellose sodium (a disintegrant), magnesium stearate, silicon dioxide, sodium carboxymethylcellulose, dextrin, dextrose, and soy lecithin.

Does it work?

Not established
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed
Not established

The graded evidence we hold for these ingredients covers different conditions than the ones this product is marketed for, so there's no established rating for its stated use.

Why this rating?
  • The label markets this product for: PMS support.
  • We looked for evidence on: Dysmenorrhea, Menopausal symptoms, Premenstrual syndrome, Menstrual irregularity.
  • The closest evidence on file: Passion Flower is rated "Insufficient Reliable Evidence To Rate" for Menopausal symptoms (Natural Medicines).
  • Also on file: Dong Quai is rated "Insufficient Reliable Evidence To Rate" for Menopausal symptoms, Premenstrual syndrome (PMS), Dysmenorrhea.

The evidence for Tang Kuei Plus as a complete product is not established in our data. Individually, vitamin C is effective for vitamin C deficiency and possibly effective for anemia of chronic disease, atrial fibrillation, cataracts, and exercise-induced respiratory infections.

Passionflower extract is possibly effective for insomnia and pre-procedural anxiety, though the evidence for alcohol use disorder and benzodiazepine withdrawal is insufficient. Tang Kuei root extract has insufficient reliable evidence for the conditions it's traditionally used for, including iron deficiency anemia, osteoporosis, coronary heart disease, migraine headache, and atopic dermatitis.

If you're considering this product for a specific health goal, talk with your doctor or pharmacist about what the current evidence shows.

The evidence, ingredient by ingredient Vitamin C Passion Flower Dong Quai

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 3 of the 3 matched ingredients.
  • Pregnancy & breastfeeding safety ratings cover 3 of 3.
  • General safety write-ups exist for 3 of 3.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Vitamin C at normal supplement doses is generally well tolerated, though high doses can cause abdominal cramps, heartburn, diarrhea, nausea, and kidney stones in susceptible people. Passionflower is generally well tolerated short-term but commonly causes drowsiness, dizziness, and confusion.

There's a rare case report of severe nausea, vomiting, prolonged QT interval, and heart rhythm changes with high-dose passionflower extract. Tang Kuei is generally well tolerated with minor side effects like burping and flatulence, but it may increase skin sensitivity to sunlight and contains constituents that are theoretically carcinogenic, though the risk at supplement doses is unclear.

Regarding pregnancy: vitamin C at normal dietary amounts is likely safe, but high-dose supplements should be avoided unless your doctor advises otherwise. Passionflower is possibly unsafe in pregnancy due to lack of safety data and potential effects on the uterus.

Tang Kuei is possibly unsafe in pregnancy because it may stimulate the uterus and affect bleeding. Neither passionflower nor Tang Kuei has enough safety information for breastfeeding, so both are best avoided while nursing.

Talk with your doctor or pharmacist about whether this product is right for you if you're pregnant or breastfeeding.

Side effects, ingredient by ingredient Vitamin C Passion Flower Dong Quai

Meds to double-check

Major interaction found
Known Interaction Concern · database check
Major identified

At least one ingredient has a documented Major-severity interaction. Check your medications for a personalized result.

Why this rating?
  • 3 of the 3 matched ingredients can interact with medications — Passion Flower, Dong Quai, Vitamin C.
  • The most serious interaction on file is rated Major.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs; cancer treatments.
  • For scale: 986 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

Before taking Tang Kuei Plus, double-check with your doctor or pharmacist if you take warfarin or other blood thinners and anticoagulant or antiplatelet drugs—Tang Kuei raises bleeding risk significantly. Also check if you take estrogens (birth control or hormone therapy), chemotherapy drugs, levothyroxine (thyroid medication), antiretroviral drugs like indinavir, sedatives or other central nervous system depressants, or aluminum-containing compounds.

Vitamin C in this product can affect how all of these work.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with no established evidence rating for its marketed use. Major medication interactions have been identified, and safety information is well characterized.

Tang Kuei Plus may appeal to someone seeking traditional herbal support, but it carries real medication interactions—especially if you take blood thinners, birth control, thyroid medication, or sedatives. If you take any prescription drugs or are pregnant or nursing, check with your doctor or pharmacist before starting this product.

The effectiveness of the combination for any specific condition isn't established, so be clear on what you're hoping it will do.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 3 of 3 active ingredients matched to our full ingredient reviews (monographs). Based on the product label dated Sep 24, 2019.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about Tang Kuei Plus, straight from the product label.

Brand Herbalife
Barcode (UPC) 0566US
Net contents 60 Tablet(s)
Market status On market
Date entered into DSLD Sep 24, 2019
DSLD ID 202183
Product type Botanical With Nutrients
Supplement form Tablet Or Pill
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Kosher, Adult Female (18 - 50 Years)
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for Tang Kuei Plus by Herbalife, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
1 Tablet(s)
Maximum serving Sizes:
1 Tablet(s)
Servings per container
60
UPC/BARCODE
0566US
IngredientAmount% DV
Vitamin C8 mg9%
Passionflower extract30 mg--
Tang Kuei root extract200 mg--

Other ingredients: Microcrystalline Cellulose, modified Food Starch, Stearic Acid, Croscarmellose Sodium, Magnesium Stearate, Silicon Dioxide, Sodium Carboxymethylcellulose, Dextrin, Dextrose, Soy Lecithin

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
FDA Disclaimer Statement

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.

Formula

For PMS support

Strictly Kosher Rabbi S. D. Krausz Vaad Hakashrus D’Udvary

Contains soy and wheat.

Tang Kuei Plus is formulated with Dong Quai root, which has been traditionally used for PMS support.

Seals/Symbols

Strictly Kosher Rabbi S. D. Krausz Vaad Hakashrus D’Udvary

FDA Statement of Identity

Dietary Supplement

Precautions

Contains soy and wheat.

Notice: Not recommended for pregnant or lactating women.

Suggested/Recommended/Usage/Directions

Recommended use: Take 1 tablet 3 times per day.

General Statements

30-day money-back guarantee. This exclusively formulated product is only available through Herbalife Independent Distributors.

Recycle this bottle Made in USA with US and imported ingredients

Brand IP Statement(s)

2017 Herbalife

General

L0566US-03 SKU0566

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

Tang Kuei Plus by Herbalife label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

Tang Kuei Plus label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in Tang Kuei Plus by Herbalife

These are the 3 active ingredients this product is made of. Select any to open its full monograph.

Serving size1 Tablet(s) Dosage formTablet Or Pill Servings per container60 Amounts shown are per serving.

Most supplement products combine several ingredients, and a medication can interact with the product through any one of them. Each ingredient below shows whether it has known drug interactions.

Vitamin C

Interacts with
207 drugs
8 mg per serving Form: Ascorbic Acid

Vitamin C (ascorbic acid) is an essential nutrient your body needs but cannot make, so you must get it from food or supplements. It's important for im...

Vitamin C monograph & interactions

Passionflower extract

Interacts with
836 drugs
30 mg per serving

Passion flower is a traditional calming herb that many people use for anxiety and sleep. Early studies hint it may help with mild anxiety and restless...

Passionflower extract monograph & interactions

Tang Kuei root extract

Interacts with
163 drugs
200 mg per serving

Dong Quai is a traditional Chinese herb often called "female ginseng" and is mostly used for menstrual and menopausal complaints. High-quality scienti...

Tang Kuei root extract monograph & interactions

Other (inactive) ingredients: Microcrystalline Cellulose, Modified Food Starch, Stearic Acid, Croscarmellose Sodium, Magnesium Stearate, Silicon Dioxide, Sodium Carboxymethylcellulose, Dextrin, Dextrose, Soy Lecithin. These complete the product’s ingredient list but are not active constituents.

Interaction report

Tang Kuei Plus by Herbalife Drug Interactions

Want to check YOUR meds against Tang Kuei Plus?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

 Go to the checker
985Drugs
2 Major 444 Moderate 539 Minor

Ingredients driving the most interactions

Passionflower extract 836
Vitamin C 207
Tang Kuei root extract 163

Individual Drug Interactions

The ingredients in Tang Kuei Plus interact with 985 drugs. Click any drug to see the details.

3 of the 3 ingredients in Tang Kuei Plus interact with drugs. Each result below shows which ingredient is responsible. Passionflower extract Vitamin C Tang Kuei root extract

Each ingredient & the kinds of drugs it affects

For each ingredient in Tang Kuei Plus with known interactions, here are the types of medications they can affect. Open any type for the detail — or search your exact drug in the checker above.

Passionflower extract3 drug types · 836 drugs

Cns Depressants

Concomitant use of passion flower with sedative drugs might cause additive effects and side effects.
Research in animals and humans shows that passion flower has sedative effects which can be additive when used with sedative medications like lorazepam.

Likelihood Possible Evidence D
Cytochrome P450 3A4 (Cyp3A4) Substrates

Theoretically, passion flower might decrease the effects of CYP3A4 substrates.
In vitro research suggests that passion flower can induce CYP3A4 enzymes, albeit to a much lower degree than rifampin, a known CYP3A4 inducer.

Likelihood Possible Evidence D
Organic Anion-Transporting Polypeptide Substrates (Oatp)

Theoretically, passion flower might reduce the bioavailability of OATP2B1 and OATP1A2 substrates.
In vitro research shows that the passion flower constituents apigenin and vitexin inhibit OATP2B1 and OATP1A2. This inhibition may be dose-dependent. One specific high-flavonoid passion flower extract (Valverde) seems to inhibit OATP2B1 and OATP1A2, while another extract with a lower flavonoid concentration (Arkocaps) shows less potent inhibition. OATPs are responsible for the uptake of drugs and other compounds into the body; however, the specific activities of OATP2B1 and OATP1A2 are not well characterized.

Likelihood Possible Evidence D
Passionflower extract full monograph & interactions

Vitamin C13 drug types · 207 drugs

Alkylating Agents

Theoretically, antioxidant effects of vitamin C might reduce the effectiveness of alkylating agents.
The use of antioxidants like vitamin C during chemotherapy is controversial. There is concern that antioxidants could reduce the activity of chemotherapy drugs that generate free radicals, such as cyclophosphamide, chlorambucil, carmustine, busulfan, and thiotepa. In contrast, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that could interfere with apoptosis (cell death) of cancer cells. More evidence is needed to determine what effect, if any, antioxidants such as vitamin C have on chemotherapy.

Likelihood Possible Evidence D
Aluminum

Vitamin C can increase the amount of aluminum absorbed from aluminum compounds.
Research in animals and humans shows that vitamin C increases aluminum absorption, theoretically by chelating aluminum and keeping it in solution where it is available for absorption. In people with normal renal function, urinary excretion of aluminum will likely increase, making aluminum retention and toxicity unlikely. Patients with renal failure who take aluminum-containing compounds such as phosphate binders should avoid vitamin C supplements in doses above the recommended dietary allowances.

Likelihood Probable Evidence B
Antitumor Antibiotics

Theoretically, the antioxidant effects of vitamin C might reduce the effectiveness of antitumor antibiotics.
The use of antioxidants like vitamin C during chemotherapy is controversial. There is concern that antioxidants could reduce the activity of chemotherapy drugs which generate free radicals, such as doxorubicin. In contrast, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that could interfere with apoptosis (cell death) of cancer cells. More evidence is needed to determine what effects, if any, antioxidants such as vitamin C have on chemotherapy.

Likelihood Possible Evidence D
Estrogens

Vitamin C might increase blood levels of estrogens.
Increases in plasma estrogen levels of up to 55% occur under some circumstances when vitamin C is taken concurrently with oral contraceptives or hormone replacement therapy, including topical products. It is suggested that vitamin C prevents oxidation of estrogen in the tissues, regenerates oxidized estrogen, and reduces sulfate conjugation of estrogen in the gut wall. When tissue levels of vitamin C are high, these processes are already maximized and supplemental vitamin C does not have any effect on estrogen levels. Increases in plasma estrogen levels may occur when patients who are deficient in vitamin C take supplements. Monitor these patients for estrogen-related side effects.

Likelihood Probable Evidence B
Fluphenazine (Prolixin)

Theoretically, vitamin C might decrease levels of fluphenazine.
In one patient there was a clinically significant decrease in fluphenazine levels when vitamin C (500 mg twice daily) was started. The mechanism is not known, and there is no further data to confirm this interaction.

Likelihood Possible Evidence D
Indinavir (Crixivan)

Vitamin C can modestly reduce indinavir levels.
One pharmacokinetic study shows that taking vitamin C 1 gram orally once daily along with indinavir 800 mg orally three times daily reduces the area under the concentration-time curve of indinavir by 14%. The mechanism of this interaction is unknown, but it is unlikely to be clinically significant in most patients. The effect of higher doses of vitamin C on indinavir levels is unknown.

Likelihood Probable Evidence B
Levothyroxine (Synthroid, Others)

Vitamin C can increase levothyroxine absorption.
Two clinical studies in adults with poorly controlled hypothyroidism show that swallowing levothyroxine with a glass of water containing vitamin C 500-1000 mg in solution reduces thyroid stimulating hormone (TSH) levels and increases thyroxine (T4) levels when compared with taking levothyroxine alone. This suggests that vitamin C increases the oral absorption of levothyroxine, possibly due to a reduction in pH.

Likelihood Probable Evidence B
Warfarin (Coumadin)

High-dose vitamin C might reduce the levels and effectiveness of warfarin.
Vitamin C in high doses may cause diarrhea and possibly reduce warfarin absorption. There are reports of two people who took up to 16 grams daily of vitamin C and had a reduction in prothrombin time. Lower doses of 5-10 grams daily can also reduce warfarin absorption. In many cases, this does not seem to be clinically significant. However, a case of warfarin resistance has been reported for a patient who took vitamin C 500 mg twice daily. Cessation of vitamin C supplementation resulted in a rapid increase in international normalized ratio (INR). Tell patients taking warfarin to avoid taking vitamin C in excessively high doses (greater than 10 grams daily). Lower doses may be safe, but the anticoagulation activity of warfarin should be monitored. Patients who are stabilized on warfarin while taking vitamin C should avoid adjusting vitamin C dosage to prevent the possibility of warfarin resistance.

Likelihood Possible Evidence D
Acetaminophen (Tylenol, Others)

High-dose vitamin C might slightly prolong the clearance of acetaminophen.
A small pharmacokinetic study in healthy volunteers shows that taking high-dose vitamin C (3 grams) 1.5 hours after taking acetaminophen 1 gram slightly increases the apparent half-life of acetaminophen from around 2.3 hours to 3.1 hours. Ascorbic acid competitively inhibits sulfate conjugation of acetaminophen. However, to compensate, elimination of acetaminophen glucuronide and unconjugated acetaminophen increases. This effect is not likely to be clinically significant.

Likelihood Probable Evidence B
Aspirin

Acidification of the urine by vitamin C might increase aspirin levels.
It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels. However, short-term use of up to 6 grams daily of vitamin C does not seem to affect urinary pH or salicylate excretion, suggesting this interaction is not clinically significant.

Likelihood Possible Evidence B
Choline Magnesium Trisalicylate (Trilisate)

Acidification of the urine by vitamin C might increase choline magnesium trisalicylate levels.
It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels. However, short-term use of up to 6 grams daily of vitamin C does not seem to affect urinary pH or salicylate excretion, suggesting this interaction probably is not clinically significant.

Likelihood Possible Evidence B
Niacin

Vitamin C might decrease the beneficial effects of niacin on high-density lipoprotein (HDL) cholesterol levels.
A combination of niacin and simvastatin (Zocor) effectively raises HDL cholesterol levels in patients with coronary disease and low HDL levels. Clinical research shows that taking a combination of antioxidants (vitamin C, vitamin E, beta-carotene, and selenium) along with niacin and simvastatin (Zocor) attenuates this rise in HDL, specifically the HDL-2 and apolipoprotein A1 fractions, by more than 50% in patients with coronary disease. It is not known whether this adverse effect is due to a single antioxidant such as vitamin C, or to the combination. It also is not known whether it will occur in other patient populations.

Likelihood Possible Evidence A
Salsalate (Disalcid)

Acidification of the urine by vitamin C might increase salsalate levels.
It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels. However, short-term use of up to 6 grams/day vitamin C does not seem to affect urinary pH or salicylate excretion, suggesting this interaction probably is not clinically significant.

Likelihood Possible Evidence B
Vitamin C full monograph & interactions

Tang Kuei root extract3 drug types · 163 drugs

Warfarin (Coumadin)

Dong quai may increase the risk of bleeding when used with warfarin.
Case reports suggest that concomitant use of dong quai with warfarin can increase the anticoagulant effects of warfarin and increase the risk of bleeding. In one case, after 4 weeks of taking dong quai 565 mg once or twice daily, the international normalized ratio (INR) increased to 4.9. The INR normalized 4 weeks after discontinuation of dong quai.

Likelihood Probable Evidence D
Anticoagulant/Antiplatelet Drugs

Theoretically, dong quai may increase the risk of bleeding when used with anticoagulant or antiplatelet drugs; however, research is conflicting.
Animal studies suggest that dong quai has antithrombin activity and inhibits platelet aggregation due to its coumarin components. Additionally, some case reports in humans suggest that dong quai can increase the anticoagulant effects of warfarin. However, clinical research in healthy adults shows that taking 1 gram of dong quai root daily for 3 weeks does not significantly inhibit platelet aggregation or cause bleeding. Until more is known, use dong quai with caution in patients taking antiplatelet/anticoagulant drugs.

Likelihood Possible Evidence D
Estrogens

Theoretically, dong quai may reduce the effects of estrogens.
Dong quai has estrogenic effects. Theoretically, concomitant use of large amounts of dong quai might interfere with hormone replacement therapy due to competition for estrogen receptors.

Likelihood Possible Evidence D
Tang Kuei root extract full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Tang Kuei Plus, from the product label.

Herbalife

Name
Herbalife International of America, Inc.
Street Address
800 W. Olympic Blvd., Suite 406
City
Los Angeles
State
CA
ZipCode
90015
Pharmacist Counseling Corner

Tang Kuei Plus by Herbalife: Common Questions

Does Tang Kuei Plus by Herbalife interact with any medications?
Yes. Based on its ingredients, Tang Kuei Plus has a known interaction with 985 medications, including 2 rated major. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Tang Kuei Plus contains 3 active ingredients, and an interaction can come from any of them. We check every ingredient, combine the results into one list per medication, and show which ingredient and mechanism is responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
Can I take Tang Kuei Plus if I'm on birth control pills?
You should check with your doctor or pharmacist first. Vitamin C in this product may increase blood levels of estrogens from birth control by up to 55%, which could affect how well the pill works or increase the risk of side effects.
Will Tang Kuei Plus make me drowsy?
Passionflower extract is commonly associated with drowsiness, dizziness, and confusion. If you're sensitive to sedating herbs or need to stay alert, this may not be the right choice for you.
Is Tang Kuei Plus safe during pregnancy?
No, the safety data advises against it. Passionflower and Tang Kuei are both possibly unsafe in pregnancy because they may affect the uterus and bleeding. Talk with your doctor before taking any supplement while pregnant.
What does Tang Kuei root extract do?
Tang Kuei is a traditional Chinese herbal root included in this product, but we don't have reliable evidence that it works for any specific condition in our data. If you're taking it for a particular reason, ask your pharmacist or doctor what the research actually shows.
Can I take Tang Kuei Plus with my blood thinner?
Tang Kuei can increase bleeding risk when combined with warfarin and other blood thinners. This is a Major concern, so you must check with your doctor or pharmacist before adding this product to your regimen.
What are the inactive ingredients in Tang Kuei Plus?
The tablet contains microcrystalline cellulose, modified food starch, stearic acid, croscarmellose sodium, magnesium stearate, silicon dioxide, sodium carboxymethylcellulose, dextrin, dextrose, and soy lecithin as binders, disintegrants, and fillers.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Not sure if Tang Kuei Plus is safe with your meds?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

Tang Kuei Plus label
Go deeper

The Full Monographs Behind Tang Kuei Plus’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Vitamin C

Interacts with 207 drugs

Vitamin C (ascorbic acid) is an essential nutrient your body needs but cannot make, so you must get it from food or supplements. It's important for immune function, collagen, and acts as an...

Read the full Vitamin C monograph → Herb & supplement monograph

Passion Flower

Interacts with 836 drugs

Passion flower is a traditional calming herb that many people use for anxiety and sleep. Early studies hint it may help with mild anxiety and restlessness, but the evidence is limited and mo...

Read the full Passion Flower monograph → Herb & supplement monograph

Dong Quai

Interacts with 163 drugs

Dong Quai is a traditional Chinese herb often called "female ginseng" and is mostly used for menstrual and menopausal complaints. High-quality scientific evidence that it works for these use...

Read the full Dong Quai monograph →
Sources

Sources & How We Checked

Tang Kuei Plus's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

The 89 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Vitamin C 51 references
  1. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
  2. Back DJ, Breckenridge AM, MacIver M, et al. Interaction of ethinyloestradiol with ascorbic acid in man. Br Med J (Clin Res Ed) 1981;282:1516.
  3. Morris JC, Beeley L, Ballantine N. Interaction of ethinyloestradiol with ascorbic acid in man [letter]. Br Med J (Clin Res Ed) 1981;283:503.
  4. Labriola D, Livingston R. Possible interactions between dietary antioxidants and chemotherapy. Oncology 1999;13:1003-8.
  5. Dwyer JH, Merz NB, Shirocre AM, et al. Progression of early atherosclerosis and intake of vitamin C and vitamin E from supplements and food. The Los Angeles Atherosclerosis Study. 41st Annual Conference on Cardiovascular Disease Epidemiology and Prevent
  6. Levine M, Rumsey SC, Daruwala R, et al. Criteria and recommendations for vitamin C intake. JAMA 1999;281:1415-23. PubMed
  7. Hansten PD, Horn JR. Drug Interactions Analysis and Management. Vancouver, WA: Applied Therapeutics Inc., 1997 and updates.
  8. Segal S, Kaminski S. Drug-nutrient interactions. American Druggist 1996 Jul;42-8.
  9. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: National Academy Press, 2000. Available at: http://www.nap.edu/books/0309069351/html/.
  10. Houston JB, Levy G. Drug biotransformation interactions in man VI: Acetaminophen and ascorbic acid. J Pharm Sci 1976;65:1218-21. PubMed
  11. Brown BG, Zhao XQ, Chait A, et al. Simvastatin and niacin, antioxidant vitamins, or the combination for the prevention of coronary disease. N Engl J Med 2001;345:1583-93. DOI
  12. Rosenthal G. Interaction of ascorbic acid and warfarin. JAMA 1971;215:1671. DOI
  13. Hume R, Johnstone JM, Weyers E. Interaction of ascorbic acid and warfarin. JAMA 1972;219:1479. DOI
  14. Smith EC, Skalski RJ, Johnson GC, Rossi GV. Interaction of ascorbic acid and warfarin. JAMA 1972;221:1166. DOI
  15. Traxer O, Huet B, Poindexter J, et al. Effect of ascorbic acid consumption on urinary stone risk factors. J Urol 2003;170:397-401.. PubMed
  16. Domingo JL, Gomez M, Llobet JM, Richart C. Effect of ascorbic acid on gastrointestinal aluminum absorption (letter). Lancet 1991;338:1467.
  17. Domingo JL, Gomez M, Llobet JM, Corbella J. Influence of some dietary constituents on aluminum absorption and retention in rats. Kidney Int 1991;39:598-601. PubMed
  18. Partridge NA, Regnier FE, White JL, Hem SL. Influence of dietary constituents on intestinal absorption of aluminum. Kidney Int 1989;35:1413-7. PubMed
  19. Mc Leod DC, Nahata MC. Inefficacy of ascorbic acid as a urinary acidifier (letter). N Engl J Med 1977;296:1413. DOI
  20. Hansten PD, Hayton WL. Effect of antacid and ascorbic acid on serum salicylate concentration. J Clin Pharmacol 1980;20:326-31. PubMed
  21. Dysken MW, Cumming RJ, Channon RA, Davis JM. Drug interaction between ascorbic acid and fluphenazine. JAMA 1979;241:2008. DOI
  22. Vihtamaki T, Parantainen J, Koivisto AM, et al. Oral ascorbic acid increases plasma oestradiol during postmenopausal hormone replacement therapy. Maturitas 2002;42:129-35. PubMed
  23. Slain D, Amsden JR, Khakoo RA, et al. Effect of high-dose vitamin C on the steady-state pharmacokinetics of the protease inhibitor indinavir in healthy volunteers. Pharmacotherapy 2005;25:165-70. PubMed
  24. Cheung MC, Zhao XQ, Chait A, et al. Antioxidant supplements block the response of HDL to simvastatin-niacin therapy in patients with coronary artery disease and low HDL. Arterioscler Thromb Vasc Biol 2001;21:1320-6. PubMed
  25. Feetam CL, Leach RH, Meynell MJ. Lack of a clinically important interaction between warfarin and ascorbic acid. Toxicol Appl Pharmacol 1975;31:544-7. PubMed
  26. Weintraub M, Griner PF. Warfarin and ascorbic acid: lack of evidence for a drug interaction. Toxicol Appl Pharmacol 1974;28:53-6. PubMed
  27. Lee DH, Folsom AR, Harnack L, et al. Does supplemental vitamin C increase cardiovascular disease risk in women with diabetes? Am J Clin Nutr 2004;80:1194-200. PubMed
  28. Taylor EN, Stampfer MJ, Curhan GC. Dietary factors and the risk of incident kidney stones in men: new insights after 14 years of follow-up. J Am Soc Nephrol 2004;15:3225-32. PubMed
  29. Ward NC, Hodgson JM, Croft KD, et al. The combination of vitamin C and grape-seed polyphenols increases blood pressure: a randomized, double-blind, placebo-controlled trial. J Hypertens 2005;23:427-34.. PubMed
  30. Prasad KN. Rationale for using high-dose multiple dietary antioxidants as an adjunct to radiation therapy and chemotherapy. J Nutr 2004;134:3182S-3S. PubMed
  31. Conklin KA. Cancer chemotherapy and antioxidants. J Nutr 2004;134:3201S-3204S. PubMed
  32. Fairweather-Tait S, Hickson K, McGaw B, et al. Orange juice enhances aluminium absorption from antacid preparation. Eur J Clin Nutr. 1994;48(1):71-3.
  33. Gruenwald, J., Graubaum, H. J., Busch, R., and Bentley, C. Safety and tolerance of ester-C compared with regular ascorbic acid. Adv.Ther. 2006;23(1):171-178.
  34. Rahimi, R., Nikfar, S., Rezaie, A., and Abdollahi, M. A meta-analysis on the efficacy and safety of combined vitamin C and E supplementation in preeclamptic women. Hypertens.Pregnancy. 2009;28(4):417-434. PubMed
  35. Einerson, B., Nathorn, C., Kitiyakara, C., Sirada, M., and Thamlikitkul, V. The efficacy of ascorbic acid in suboptimal responsive anemic hemodialysis patients receiving erythropoietin: a meta-analysis. J Med.Assoc.Thai. 2011;94 Suppl 1:S134-S146.
  36. Li, G., Li, L., Yu, C., and Chen, L. Effect of vitamins C and E supplementation on Helicobacter pylori eradication: a meta-analysis. Br.J Nutr 2011;106(11):1632-1637.
  37. Chen X, Shen L, Gu X, et al. High-dose supplementation with vitamin C--induced pediatric urolithiasis: the first case report in a child and literature review. Urology. 2014;84(4):922-4. PubMed
  38. Sattar A, Willman JE, Kolluri R. Possible warfarin resistance due to interaction with ascorbic acid: case report and literature review. Am J Health Syst Pharm. 2013;70(9):782-6. PubMed
  39. Yaich S, Chaabouni Y, Charfeddine K, et al. Secondary oxalosis due to excess vitamin C intake: a cause of graft loss in a renal transplant recipient. Saudi J Kidney Dis Transpl. 2014;25(1):113-6. PubMed
  40. Jalloh MA, Gregory PJ, Hein D, et al. Dietary supplement interactions with antiretrovirals: a systematic review. Int J STD AIDS. 2017 Jan;28(1):4-15. PubMed
  41. Rumbold A, Ota E, Nagata C, Shahrook S, Crowther CA. Vitamin C supplementation in pregnancy. Cochrane Database Syst Rev. 2015;(9):CD004072. PubMed
  42. Seo MS, Kim JK, Shim JY. High-dose vitamin C promotes regression of multiple pulmonary metastases originating from hepatocellular carcinoma. Yonsei Med J. 2015;56(5):1449-52. PubMed
  43. Skelin M, Lucijanic T, Amidzic Klaric D, et al. Factors Affecting Gastrointestinal Absorption of Levothyroxine: A Review. Clin Ther. 2017 Feb;39(2):378-403. PubMed
  44. Jiang K, Tang K, Liu H, Xu H, Ye Z, Chen Z. Ascorbic acid supplements and kidney stones incidence among men and women: a systematic review and meta-analysis. Urol J. 2019;16(2):115-120.
  45. Thomas S, Patel D, Bittel B, et al. Effect of High-Dose Zinc and Ascorbic Acid Supplementation vs Usual Care on Symptom Length and Reduction Among Ambulatory Patients With SARS-CoV-2 Infection: The COVID A to Z Randomized Clinical Trial. JAMA Netw Open. 2 PubMed
  46. Giffen MA, McLemore JL. Hyperoxalosis Secondary to Intravenous Vitamin C Administration as a Non-Allopathic Treatment for Cancer. Acad Forensic Pathol 2019;9(1-2):118-126. PubMed
  47. Maike A, Sturgill D, Gallan A. Oxalate Nephropathy in a Renal Transplant Recipient After Receiving High Dose Ascorbic Acid. Am J Med Sci 2021. PubMed
  48. Shen ZY, Chen YR, Wang MC, Chang SS. High-dose vitamin C-induced acute oxalate nephropathy in a renal transplant recipient: a case report and literature review. Asian J Surg 2022. PubMed
  49. Yanase F, Spano S, Maeda A, et al. Mega-dose sodium ascorbate: a pilot, single-dose, physiological effect, double-blind, randomized, controlled trial. Crit Care 2023;27(1):371. PubMed
  50. Sharma Y, Sumanadasa S, Shahi R, et al. Efficacy and safety of vitamin C supplementation in the treatment of community-acquired pneumonia: a systematic review and meta-analysis with trial sequential analysis. Sci Rep 2024;14(1):11846. PubMed
  51. Pejcic AV, Petrovic NZ, Djordjic MD, Milosavljevic MN. Vitamin C Levels in Pregnant Women and the Efficacy of Vitamin C Supplements in Preventing Premature Rupture of Membranes: A Systematic Review and Meta-Analysis. Balkan Med J 2024;41(4):248-260. PubMed

See these in context on the Vitamin C monograph →

Passion Flower 19 references
  1. Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.
  2. The Review of Natural Products by Facts and Comparisons. St. Louis, MO: Wolters Kluwer Co., 1999.
  3. Fisher AA, Purcell P, Le Couteur DG. Toxicity of Passiflora incarnata L. J Toxicol Clin Toxicol 2000;38:63-6.
  4. Akhondzadeh S, Naghavi HR, Shayeganpour A, et al. Passionflower in the treatment of generalized anxiety: a pilot double-blind randomized controlled trial with oxazepam. J Clin Pharm Ther 2001;26:363-7. PubMed
  5. Farnsworth N, Bingel A, Cordell G, et al. Potential value of plants as sources of new antifertility agents I. J Pharm Sci 1975;64:535-98. DOI
  6. Mori A, Hasegawa K, Murasaki M, et al. Clinical evaluation of Passiflamin (passiflora extract) on neurosis - multicenter double blind study in comparison with mexazolam. Rinsho Hyoka (Clinical Evaluation) 1993;21:383-440.
  7. Miyasaka LS, Atallah AN, Soares BG. Passiflora for anxiety disorder. Cochrane Database Syst Rev 2007;(1):CD004518. DOI
  8. Speroni E., Minghetti A. Neuropharmacological activity of extracts from Passiflora incarnata. Planta Med. 1988;54:488-91.
  9. Capasso A., Sorrentino L. Pharmacological studies on the sedative and hypnotic effect of Kava kava and Passiflora extracts combination. Phytomedicine. 2005;12:39-45. PubMed
  10. Carrasco MC, Vallejo JR, Pardo-de-Santayana M, et al. Interactions of Valeriana officinalis L. and Passiflora incarnata L. in a patient treated with lorazepam. Phytother Res. 2009 Dec;23:1795-6.
  11. Smith, G. W., Chalmers, T. M., and Nuki, G. Vasculitis associated with herbal preparation containing Passiflora extract. Br J Rheumatol. 1993;32(1):87-88.
  12. Soulimani, R., Younos, C., Jarmouni, S., Bousta, D., Misslin, R., and Mortier, F. Behavioural effects of Passiflora incarnata L. and its indole alkaloid and flavonoid derivatives and maltol in the mouse. J Ethnopharmacol. 1997;57(1):11-20. PubMed
  13. Nojoumi M, Ghaeli P, Salimi S, Sharifi A, Raisi F. Effects of Passion Flower Extract, as an Add-On Treatment to Sertraline, on Reaction Time in Patients ?with Generalized Anxiety Disorder: A Double-Blind Placebo-Controlled Study. Iran J Psychiatry. 2016;1
  14. Rokhtabnak F, Ghodraty MR, Kholdebarin A, et al. Comparing the Effect of Preoperative Administration of Melatonin and Passiflora incarnata on Postoperative Cognitive Disorders in Adult Patients Undergoing Elective Surgery. Anesth Pain Med. 2016;7(1):e4123 PubMed
  15. Dantas LP, de Oliveira-Ribeiro A, de Almeida-Souza LM, Groppo FC. Effects of passiflora incarnata and midazolam for control of anxiety in patients undergoing dental extraction. Med Oral Patol Oral Cir Bucal. 2017;22(1):e95-e101. PubMed
  16. Ozturk Z, Kalayci CC. Pregnancy outcomes in psychiatric patients treated with passiflora incarnata. Complement Ther Med. 2018 Feb;36:30-32. PubMed
  17. da Cunha RS, Amorim KS, Gercina AC, et al. Herbal medicines as anxiolytics prior to third molar surgical extraction. A randomized controlled clinical trial. Clin Oral Investig. 2020. PubMed
  18. Schäfer AM, Gilgen PM, Spirgi C, et al. Constituents of Passiflora incarnata, but Not of Valeriana officinalis, Interact with the Organic Anion Transporting Polypeptides (OATP)2B1 and OATP1A2. Planta Med. 2021. PubMed
  19. Mazzari ALDA, Lacerda MG, Milton FA, et al. In vitro effects of European and Latin-American medicinal plants in CYP3A4 gene expression, glutathione levels, and P-glycoprotein activity. Front Pharmacol 2022;13:826395. PubMed

See these in context on the Passion Flower monograph →

Dong Quai 19 references
  1. Hirata JD, Swiersz LM, Zell B, et al. Does dong quai have estrogenic effects in postmenopausal women? A double-blind, placebo-controlled trial. Fertil Steril 1997;68:981-6. PubMed
  2. Page RL II, Lawrence JD. Potentiation of warfarin by dong quai. Pharmacotherapy 1999;19:870-6. PubMed
  3. Heck AM, DeWitt BA, Lukes AL. Potential interactions between alternative therapies and warfarin. Am J Health Syst Pharm 2000;57:1221-7. DOI
  4. Eagon PK, Elm MS, Hunter DS, et al. Medicinal herbs: modulation of estrogen action. Era of Hope Mtg, Dept Defense; Breast Cancer Res Prog, Atlanta, GA 2000;Jun 8-11.
  5. Dr. Duke's Phytochemical and Ethnobotanical Databases. Available at: http://www.ars-grin.gov/duke/.
  6. Amato P, Christophe S, Mellon PL. Estrogenic activity of herbs commonly used as remedies for menopausal symptoms. Menopause 2002;9:145-50. PubMed
  7. Shi M, Chang L, He G. [Stimulating action of Carthamus tinctorius L., Angelica sinensis (Oliv.) Diels and Leonurus sibiricus L. on the uterus]. Zhongguo Zhong Yao Za Zhi 1995;20:173-5, 192.
  8. Hoult JR, Paya M. Pharmacological and biochemical actions of simple coumarins: natural products with therapeutic potential. Gen Pharmacol 1996;27:713-22.. PubMed
  9. Cheong JL, Bucknall R. Retinal vein thrombosis associated with a herbal phytoestrogen preparation in a susceptible patient. Postgrad Med J 2005;81:266-7.. PubMed
  10. Chang CJ, Chiu JH, Tseng LM, et al. Modulation of HER2 expression by ferulic acid on human breast cancer MCF7 cells. Eur J Clin Invest 2006;36:588-96. PubMed
  11. Chuang CH, Doyle P, Wang JD, et al. Herbal medicines used during the first trimester and major congenital malformations: an analysis of data from a pregnancy cohort study. Drug Saf 2006;29:537-48. PubMed
  12. Lau CBS, Ho TCY, Chan TWL, Kim SCF. Use of dong quai (Angelica sinensis) to treat peri- and postmenopausal symptoms in women with breast cancer: is it appropriate? Menopause 2005;12:734-40.
  13. Ellis GR, Stephens MR. Untitled (photograph and a brief case report). BMJ 1999;319:650.
  14. Nambiar, S., Schwartz, R. H., and Constantino, A. Hypertension in mother and baby linked to ingestion of Chinese herbal medicine. West J Med 1999;171(3):152.
  15. Lee, S. K., Cho, H. K., Cho, S. H., Kim, S. S., Nahm, D. H., and Park, H. S. Occupational asthma and rhinitis caused by multiple herbal agents in a pharmacist. Ann.Allergy Asthma Immunol. 2001;86(4):469-474. PubMed
  16. Xu, J. and Li, G. [Observation on short-term effects of Angelica injection on chronic obstructive pulmonary disease patients with pulmonary hypertension]. Zhongguo Zhong Xi Yi Jie He Za Zhi 2000;20(3):187-189.
  17. Scott, G. N. and Elmer, G. W. Update on natural product--drug interactions. Am J Health Syst.Pharm 2-15-2002;59(4):339-347. PubMed
  18. Circosta, C., Pasquale, R. D., Palumbo, D. R., Samperi, S., and Occhiuto, F. Estrogenic activity of standardized extract of Angelica sinensis. Phytother.Res. 2006;20(8):665-669.
  19. Fung FY, Wong WH, Ang SK, et al. A randomized, double-blind, placebo- controlled study on the anti-haemostatic effects of Curcuma longa, Angelica sinensis and Panax ginseng. Phytomedicine. 2017;32:88-96. PubMed

See these in context on the Dong Quai monograph →

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Supplement interaction checker › Check any supplement or product against your medications Drug–drug interactions › Check two or more of your medications against each other Browse medications A–Z › Every drug we've checked against herbs & supplements NDC & pricing lookup › Find a drug’s NDCs, packaging and costs Ask a pharmacist › Free, personal answer from our licensed team