Interactions on record — worth a quick check against your medications. Based on 3 of 5 ingredients. Check your meds →
Dietary supplement

Ester-C Bio Ingredients & Drug Interactions

by Klaire Labs

Ester-C Bio label
See full label image
Capsule Category: Other Combinations
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 16, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Ester-C Bio 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: Moderate

Ester-C Bio is a dietary supplement by Klaire Labs with 5 active ingredients. Its ingredients are commonly taken for seasonal allergies, antioxidant support, heart and blood pressure health.Based on those ingredients, 1,289 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Citrus Bioflavonoids, Pycnogenol, Rutin. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

Jump to a section

Check Your Meds Against Ester-C Bio by Klaire Labs

Ask about any prescription or over-the-counter medication and we check it for interactions with Ester-C Bio by Klaire Labs — and tell you which ingredient is responsible.

Pharmacist-reviewed data Checks every ingredient Answer in seconds
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HelloPharmacist Scorecard of Ester-C Bio by Klaire Labs

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 Jul 30, 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 5 of its 5 active ingredients.
  • No proprietary blends here — you can verify the dose of every single component.

Ester-C Bio contains five active ingredients: two forms of Ester-C (a form of vitamin C we could not evaluate for interactions), citrus bioflavonoids (a plant compound that includes quercetin), rutin (another plant-derived compound), and pycnogenol (an extract from maritime pine bark). The product also holds several inactive ingredients — a vegetarian capsule, stearic acid, microcrystalline cellulose, and silicon dioxide — which are fillers and binders that help form and stabilize the capsule.

Does it work?

Moderate evidence
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
Moderate

Some clinical evidence supports this product's ingredients for its stated purpose, but it isn't conclusive.

Why this rating?
  • The label markets this product for: Vitamin C supplement.
  • We looked for evidence on: Common cold, Exercise-induced muscle damage, Exercise-induced muscle soreness, Exercise-induced respiratory infections, Hemorrhoids, Chronic venous insufficiency (CVI) — and 4 related terms.
  • The strongest evidence on file: Maritime Pine is rated "Possibly Effective" for Chronic venous insufficiency (CVI) (Natural Medicines).
  • Also on file: Rutin is rated "Insufficient Reliable Evidence To Rate" for Exercise-induced respiratory infections, Hemorrhoids.
  • Also on file: Quercetin is rated "Insufficient Reliable Evidence To Rate" for Allergic rhinitis (hay fever), Atherosclerosis, Cardiovascular disease (CVD), Chronic venous insufficiency (CVI).

The evidence for citrus bioflavonoids and rutin in this product remains incomplete. For rutin specifically, the data we hold shows insufficient evidence to rate its use against aging skin, autism spectrum disorder, inflammatory bowel disease, diabetes, respiratory infections, or hemorrhoids.

For pycnogenol (maritime pine bark), the evidence is stronger: it is possibly effective for osteoarthritis and chronic venous insufficiency (a condition in which leg veins don't return blood well to the heart). For athletic performance, quercetin is rated possibly ineffective, and evidence on its use for age-related cognitive decline, hay fever, Alzheimer disease, asthma, and atherosclerosis is insufficient to rate.

Because we could not check the Ester-C components, we cannot speak to their effectiveness from our data.

The evidence, ingredient by ingredient Quercetin Rutin Maritime Pine

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.

Quercetin and rutin are generally well tolerated at food and typical supplement doses, though high doses and long-term safety have not been well studied. Orally, quercetin may cause headache and tingling in the hands or feet; rutin may cause headache, flushing, or rashes in some people.

Pycnogenol is generally well tolerated, but may cause gastrointestinal complaints, dizziness, or vertigo. The safety notes advise against supplemental doses of quercetin and pycnogenol during pregnancy and breastfeeding because data are insufficient.

For rutin, pregnancy safety is rated likely safe, but breastfeeding safety is unknown, so supplemental doses should be avoided unless your doctor advises otherwise. We hold no pregnancy or breastfeeding data for the Ester-C components.

Side effects, ingredient by ingredient Quercetin Rutin Maritime Pine

Meds to double-check

Moderate interaction found
Known Interaction Concern · database check
Moderate identified

The most serious documented interaction for these ingredients is Moderate. Check your medications for a personalized result.

Why this rating?
  • 3 of the 3 matched ingredients can interact with medications — Rutin, Quercetin, Maritime Pine.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs; immunosuppressants / transplant drugs; diabetes medications.
  • For scale: 1,290 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 Ester-C Bio, check your exact medications with your doctor or pharmacist if you take blood thinners or antiplatelet drugs (major bleeding risk), antidiabetes medications, pravastatin or other statin drugs, warfarin, quinolone antibiotics (like ciprofloxacin), cyclosporine, sulfasalazine, mitoxantrone, or immunosuppressants. These are the drug types with documented moderate-severity interactions in this product.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with some supporting evidence for its stated purpose. Moderate medication interactions have been identified, and safety information is well characterized.

This product combines vitamin C with bioflavonoids and an herbal extract, intended to support general wellness — though robust evidence for most uses is lacking. If you take blood thinners, antidiabetes drugs, statins, quinolone antibiotics, cyclosporine, or other prescription medications, you should check with your doctor or pharmacist before starting.

Pregnant or breastfeeding women should talk with their provider first, since safety data are incomplete.

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

Assessment coverage: 3 of 5 active ingredients matched to our full ingredient reviews (monographs). Based on the product label dated Jul 21, 2022.

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 Ester-C Bio, straight from the product label.

Brand Klaire Labs
Barcode (UPC) 828054002159
Net contents 100 Vegetarian Capsule(s)
Market status On market
Date entered into DSLD Jul 21, 2022
DSLD ID 264871
Product type Other Combinations
Supplement form Capsule
Dietary claims / uses Nutrient, All Other
Intended target group(s) Adult (18 - 50 Years), Gluten Free, Dairy Free
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 Ester-C Bio by Klaire Labs, 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 Capsule(s)
Maximum serving Sizes:
1 Capsule(s)
Servings per container
100
UPC/BARCODE
828054002159
IngredientAmount% DV
Ester-C540 mg600%
Ester-C60 mg5%
Citrus Bioflavonoids50 mg--
Rutin75 mg--
Pycnogenol3 mg--

Other ingredients: Vegetarian Capsule, Stearic Acid, Microcrystalline Cellulose, Silicon Dioxide

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 Statement of Identity

Vitamin C Supplement

Formulation

Free of the following common allergens: Milk/casein, eggs, fish, shellfish, tree nuts, peanuts, wheat, gluten, and soybeans. Contains no artificial colors, flavors, or preservatives.

Produced under a strict quality management system in compliance with Good Manufacturing Practices (GMPs) and third-party quality certifications.

Suggested/Recommended/Usage/Directions

Suggested Use: 1 capsule, 1 to 2 times daily with food or as directed by a healthcare professional.

Formula

Ester-C calcium ascorbate is a non-acidic form of vitamin C manufactured by a unique water-based process that combines calcium with vitamin C. This process creates a patented mixture of mineral ascorbates and vitamin C metabolites.

Brand IP Statement(s)

Ester-C and Ester-C are registered trademarks of the Ester-C Company. Pycnogenol is a registered trademark of Horphag Research Ltd. Use of this product is protected by one or more U.S. patents and other international patents.

SFI

Precautions

Do not use if shrinkwrap is broken or missing.

Caution: If you are pregnant, nursing, have a medical condition, or taking prescription drugs, consult your physician before using this product.

Keep out of reach of children.

Storage

Store in a cool, dry place (59 degrees F - 85 degrees F) away from direct light.

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

See for yourself

Ester-C Bio by Klaire Labs label

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

Ester-C Bio 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 Ester-C Bio by Klaire Labs

These are the 5 active ingredients this product is made of. Select any to open its full monograph.

Serving size1 Capsule(s) Dosage formCapsule Servings per container100 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.

Ester-C

540 mg per serving Form: Vitamin C

Ester-C

60 mg per serving Form: Calcium

Citrus Bioflavonoids

Interacts with
1,169 drugs
50 mg per serving Form: Citrus aurantium, Citrus aurantium

Quercetin is a plant flavonoid with antioxidant and anti-inflammatory properties found in many common foods and sold as a supplement. While early rese...

Citrus Bioflavonoids monograph & interactions

Rutin

Interacts with
86 drugs
75 mg per serving Form: Japanese Pagoda Tree Bud Extract

Rutin is a plant flavonoid (often taken from buckwheat or citrus) that people use mainly for blood vessel and circulation problems like varicose veins...

Rutin monograph & interactions

Pycnogenol

Interacts with
327 drugs
3 mg per serving Form: French Maritime Pine Bark Extract

Maritime pine bark extract (often sold as Pycnogenol) is a plant-based antioxidant most studied for circulation, vein, and skin health. Some research...

Pycnogenol monograph & interactions

Other (inactive) ingredients: Vegetarian Capsule, Stearic Acid, Microcrystalline Cellulose, Silicon Dioxide. These complete the product’s ingredient list but are not active constituents.

Interaction report

Ester-C Bio by Klaire Labs Drug Interactions

Want to check YOUR meds against Ester-C Bio?

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
1,289Drugs
1,289 Moderate

Ingredients driving the most interactions

Citrus Bioflavonoids 1,169
Pycnogenol 327
Rutin 86

Individual Drug Interactions

The ingredients in Ester-C Bio interact with 1,289 drugs. Click any drug to see the details.

3 of the 5 ingredients in Ester-C Bio interact with drugs. Each result below shows which ingredient is responsible. Citrus Bioflavonoids Pycnogenol Rutin

Each ingredient & the kinds of drugs it affects

For each ingredient in Ester-C Bio 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.

Citrus Bioflavonoids21 drug types · 1,169 drugs

Antidiabetes Drugs

Theoretically, concomitant use of quercetin and antidiabetes drugs might increase the risk of hypoglycemia.

Clinical research suggests that a combination of quercetin, myricetin, and chlorogenic acid reduce levels of fasting glucose in patients with type 2 diabetes, including those already taking antidiabetes agents. The effect of quercetin alone is unknown.

Likelihood Possible Evidence B
Antihypertensive Drugs

Theoretically, taking quercetin with antihypertensive drugs might increase the risk of hypotension.

Quercetin can modestly decrease blood pressure in people with mild hypertension. Theoretically, it might have additive blood pressure lowering effects when used with antihypertensive drugs.

Likelihood Possible Evidence B
Cyclosporine (Neoral, Sandimmune)

Theoretically, concomitant use might increase the levels and adverse effects of cyclosporine.

A small study in healthy volunteers shows that pretreatment with quercetin increases plasma levels and prolongs the half-life of a single dose of cyclosporine, possibly due to inhibition of p-glycoprotein or cytochrome P450 3A4 (CYP3A4), which metabolizes cyclosporin.

Likelihood Possible Evidence B
Cytochrome P450 2C8 (Cyp2C8) Substrates

Theoretically, concomitant use might increase the levels and adverse effects of CYP2C8 substrates.

In vitro research shows that quercetin inhibits CYP2C8. Inhibition of paclitaxel (Taxol) metabolism via CYP2C8 has been reported in vitro. However, a small study in humans found no effect of quercetin on rosiglitazone (Avandia), which is also a CYP2C8 substrate.

Likelihood Possible Evidence D
Cytochrome P450 2C9 (Cyp2C9) Substrates

Theoretically, concomitant use might increase the levels and adverse effects of CYP2C9 substrates.

A small clinical study in healthy volunteers shows that taking quercetin 500 mg twice daily for 10 days prior to taking diclofenac, a CYP2C9 substrate, increases diclofenac plasma levels by 75% and prolongs the half-life by 32.5%. Animal research also shows that pretreatment with quercetin increases plasma levels and prolongs the half-life of losartan (Cozaar), a substrate of CYP2C9. Furthermore, laboratory research shows that quercetin inhibits CYP2C9.

Likelihood Possible Evidence B
Cytochrome P450 2D6 (Cyp2D6) Substrates

Theoretically, concomitant use might increase the levels and adverse effects of CYP2D6 substrates.

In vitro research show that quercetin inhibits CYP2D6. This effect has not been reported in humans.

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

Theoretically, concomitant use might alter the effects and adverse effects of CYP3A4 substrates.
A small clinical study in healthy volunteers shows that pretreatment with quercetin increases plasma levels and prolongs the half-life of a single dose of cyclosporine (Neoral, Sandimmune), a substrate of CYP3A4. Animal research also shows that pretreatment with quercetin increases plasma levels and prolongs the half-life of losartan (Cozaar) and quetiapine (Seroquel), substrates of CYP3A4. Other laboratory research also shows that quercetin inhibits CYP3A4. However, one clinical study shows that quercetin can increase the metabolism of midazolam, a substrate of CYP3A4, and decrease serum concentrations of midazolam by about 24% in some healthy individuals, suggesting possible induction of CYP3A4.

Likelihood Possible Evidence D
Diclofenac (Voltaren, Others)

Theoretically, concomitant use might increase the levels and adverse effects of diclofenac.

A small clinical study in healthy volunteers shows that taking quercetin 500 mg twice daily for 10 days prior to taking diclofenac increases diclofenac plasma levels by 75% and prolongs the half-life by 32.5%. This is thought to be due to inhibition of CYP2C9 by quercetin.

Likelihood Probable Evidence B
Losartan (Cozaar)

Theoretically, concomitant use might increase the effects and adverse effects of losartan and decrease the effects of its active metabolite.

Animal research shows that pretreatment with quercetin increases plasma levels and prolongs the half-life of losartan (Cozaar) while decreasing plasma levels of losartan's active metabolite. This metabolite, which is around 10-fold more potent than losartan, is the result of cytochrome P450 (CYP) 2C9- and CYP3A4-mediated transformation of losartan. Additionally, in vitro research shows that quercetin may inhibit P-glycoprotein-mediated efflux of losartan from the intestines, resulting in increased absorption of losartan. These results suggest that concomitant use of quercetin and losartan might increase systemic exposure to losartan while also decreasing plasma concentrations of losartan's active and more potent metabolite.

Likelihood Possible Evidence D
Midazolam (Versed)

Theoretically, concomitant use might decrease the levels and effects of midazolam.

A small clinical study in healthy volunteers shows that quercetin can increase the metabolism of midazolam, with a decrease in AUC of about 24%.

Likelihood Possible Evidence B
Mitoxantrone

Theoretically, quercetin might increase the effects and adverse effects of mitoxantrone.
In vitro research shows that quercetin increases the intracellular accumulation and cytotoxicity of mitoxantrone, possibly through inhibition of breast cancer resistance protein (BCRP), of which mitoxantrone is a substrate. So far, this interaction has not been reported in humans.

Likelihood Possible Evidence D
Organic Anion Transporter 1 (Oat1) Substrates

Theoretically, concomitant use might increase the effects and adverse effects of OAT1 substrates.

In vitro research shows that quercetin is a strong non-competitive inhibitor of OAT1, with half-maximal inhibitory concentration (IC50) values less than 10 mcM. So far, this interaction has not been reported in humans.

Likelihood Possible Evidence D
Organic Anion Transporter 3 (Oat3) Substrates

Theoretically, concomitant use might increase the effects and adverse effects of OAT3 substrates.

In vitro research shows that quercetin is a strong non-competitive inhibitor of OAT3, with half-maximal inhibitory concentration (IC50) values as low as 0.75 mcM. So far, this interaction has not been reported in humans.

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

Theoretically, concomitant use might increase the effects and adverse effects of OATP substrates.

In vitro evidence shows that quercetin can inhibit organic anion-transporting peptide (OATP) 1B1-mediated uptake of estrone-3-sulfate and pravastatin. Furthermore, clinical research in healthy males shows that intake of quercetin along with pravastatin increases the AUC of pravastatin by 24%, prolongs its half-life by 14%, and decreases its apparent clearance by 18%, suggesting that quercetin modestly inhibits the uptake of pravastatin in hepatic cells.

Likelihood Possible Evidence B
P-Glycoprotein Substrates

Theoretically, concomitant use might alter the effects and adverse effects of P-glycoprotein substrates.

There is preliminary evidence that quercetin inhibits the gastrointestinal P-glycoprotein efflux pump, which might increase the bioavailability and serum levels of drugs transported by the pump. A small study in healthy volunteers reported that pretreatment with quercetin increased bioavailability and plasma levels after a single dose of cyclosporine (Neoral, Sandimmune). Also, two small studies have shown that quercetin might decrease the absorption of talinolol, a substrate transported by the gastrointestinal P-glycoprotein efflux pump. However, in another small study, several days of quercetin treatment did not significantly affect the pharmacokinetics of saquinavir (Invirase). The reason for these discrepancies is not entirely clear. Until more is known, use quercetin cautiously in combination with P-glycoprotein substrates.

Likelihood Possible Evidence B
Pravastatin (Pravachol)

Theoretically, concomitant use might increase the effects and adverse effects of pravastatin.
In vitro evidence shows that quercetin can inhibit OATP 1B1-mediated uptake of pravastatin. Also, preliminary clinical research in healthy males shows that intake of quercetin along with pravastatin increases the maximum concentration of pravastatin by 24%, prolongs its half-life by 14%, and decreases its apparent clearance by 18%, suggesting that quercetin modestly inhibits the uptake of pravastatin in hepatic cells.

Likelihood Possible Evidence B
Prazosin (Minipress)

Theoretically, quercetin might increase the effects and adverse effects of prazosin.
In vitro research shows that quercetin inhibits the transcellular efflux of prazosin, possibly through inhibition of breast cancer resistance protein (BCRP), of which prazosin is a substrate. BCRP is an ATP-binding cassette efflux transporter in the intestines, kidneys, and liver. So far, this interaction has not been reported in humans.

Likelihood Possible Evidence D
Quetiapine (Seroquel)

Theoretically, concomitant use might increase the effects and adverse effects of quetiapine.
Animal research shows that pretreatment with quercetin can increase plasma levels of quetiapine and prolong its clearance, possibly due to inhibition of cytochrome P450 3A4 (CYP3A4) by quercetin. Additionally, the brain-to-plasma ratio of quetiapine concentrations increased, possibly due to inhibition of P-glycoprotein at the blood-brain barrier. This interaction has not been reported in humans.

Likelihood Possible Evidence D
Quinolone Antibiotics

Theoretically, concomitant use might inhibit the effects of quinolone antibiotics.
In vitro, quercetin binds to the DNA gyrase site on bacteria, which may interfere with the activity of quinolone antibiotics.

Likelihood Possible Evidence B
Sulfasalazine (Azulfidine)

Theoretically, quercetin might increase the effects and adverse effects of sulfasalazine.
Animal research shows that quercetin increases the maximum serum concentration (Cmax) and area under the curve (AUC) of sulfasalazine, possibly through inhibition of breast cancer resistance protein (BCRP), of which sulfasalazine is a substrate. So far, this interaction has not been reported in humans.

Likelihood Possible Evidence D
Warfarin (Coumadin)

Theoretically, quercetin may increase the risk of bleeding if used with warfarin.
Animal and in vitro studies show that quercetin might increase serum levels of warfarin. Quercetin and warfarin have the same human serum albumin (HSA) binding site, and in vitro research shows that quercetin has stronger affinity for the HSA binding site and can theoretically displace warfarin, causing higher serum levels of warfarin. Animal research shows that taking quercetin for 2 weeks before initiating warfarin increases the maximum serum level of warfarin by 30%, the half-life by 10%, and the overall exposure by 63% when compared with control. Concomitant administration of quercetin and warfarin, without quercetin pre-treatment, also increased these measures, but to a lesser degree. Researchers theorize that inhibition of CYP3A4 by quercetin may explain these effects. So far, this interaction has not been reported in humans.

Likelihood Possible Evidence D
Citrus Bioflavonoids full monograph & interactions

Pycnogenol3 drug types · 327 drugs

Anticoagulant/Antiplatelet Drugs

Theoretically, maritime pine bark extract might increase the risk of bleeding when used with antiplatelet or anticoagulant drugs.
Clinical research suggests that maritime pine bark extract inhibits platelet aggregation. However, the clinical significance of this effect is unclear.

Likelihood Possible Evidence D
Antidiabetes Drugs

Theoretically, maritime pine bark extract might increase the risk of hypoglycemia when used with antidiabetes drugs.
One clinical study shows that maritime pine bark extract decreases blood sugar in patients with diabetes being treated with antidiabetes agents. Monitor blood glucose levels closely. Dose adjustments might be necessary.

Likelihood Possible Evidence B
Immunosuppressants

Theoretically, maritime pine bark extract might decrease the effectiveness of immunosuppressant therapy.
In vitro and animal research suggests that maritime pine bark extract has immunostimulant activity. This effect has not been reported in humans.

Likelihood Possible Evidence D
Pycnogenol full monograph & interactions

Rutin1 drug type · 86 drugs

Antidiabetes Drugs

Theoretically, taking rutin with antidiabetes drugs might increase the risk of hypoglycemia.
Animal research suggests that rutin has hypoglycemic effects.

Likelihood Possible Evidence D
Rutin full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Ester-C Bio, from the product label.

Klaire Labs

See all Klaire Labs products
Name
SFI USA
City
Reno
State
NV
ZipCode
89521
Web Address
Klaire.com
Pharmacist Counseling Corner

Ester-C Bio by Klaire Labs: Common Questions

Does Ester-C Bio by Klaire Labs interact with any medications?
Yes. Based on its ingredients, Ester-C Bio has a known interaction with 1,289 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Ester-C Bio contains 5 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 this while pregnant?
Safety data are insufficient for two of the three checked ingredients — quercetin and pycnogenol — so supplemental doses are not recommended. Rutin is rated likely safe in pregnancy, but because this is a combined product and we could not assess the two Ester-C forms, talk with your doctor or pharmacist before taking it.
Is this safe while breastfeeding?
No — safety data do not support supplemental doses of quercetin or pycnogenol while breastfeeding. Rutin's safety while nursing is also unknown, so supplemental doses should be avoided unless your doctor advises otherwise.
What side effects might I see?
The most common are mild: quercetin may cause headache and tingling in the hands or feet; rutin may cause headache, flushing, or rashes; and pycnogenol may cause gastrointestinal upset, dizziness, or vertigo. These affect only some people and are generally rare.
Does quercetin actually work for allergies or colds?
The data we hold on quercetin for hay fever, asthma, and age-related issues shows insufficient evidence to rate it — meaning we don't have strong enough research to say whether it works. It is rated possibly ineffective for athletic performance.
What's pycnogenol supposed to do?
In the evidence we hold, maritime pine bark (pycnogenol) is possibly effective for osteoarthritis and chronic venous insufficiency — a condition where leg veins struggle to return blood to the heart. For other uses listed on product labels, evidence is either insufficient or shows it's possibly ineffective.
Why couldn't you check the Ester-C in this product?
We hold no monograph or interaction data for Ester-C itself — it's a proprietary form of vitamin C, and its interactions haven't been evaluated in our database. You can ask your pharmacist or look up the manufacturer's safety information for details.

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

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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.

Ester-C Bio label
Go deeper

The Full Monographs Behind Ester-C Bio’s Ingredients

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

Herb & supplement monograph

Quercetin

Interacts with 1,169 drugs

Quercetin is a plant flavonoid with antioxidant and anti-inflammatory properties found in many common foods and sold as a supplement. While early research is interesting for allergies, blood...

Read the full Quercetin monograph → Herb & supplement monograph

Rutin

Interacts with 86 drugs

Rutin is a plant flavonoid (often taken from buckwheat or citrus) that people use mainly for blood vessel and circulation problems like varicose veins and hemorrhoids. The evidence is limite...

Read the full Rutin monograph → Herb & supplement monograph

Maritime Pine

Interacts with 327 drugs

Maritime pine bark extract (often sold as Pycnogenol) is a plant-based antioxidant most studied for circulation, vein, and skin health. Some research is promising, but many studies are small...

Read the full Maritime Pine monograph →
Sources

Sources & How We Checked

Ester-C Bio'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 42 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.

Quercetin 26 references
  1. Shoskes DA, Zeitlin SI, Shahed A, Rajfer J. Quercetin in men with category III chronic prostatitis: A preliminary prospective, double-blind, placebo-controlled trial. Urol 1999;54:960-3. PubMed
  2. Starvic B. Quercetin in our diet: from potent mutagen to probable anticarcinogen. Clin Biochem 1994;27:245-8. PubMed
  3. Ferry DR, Smith A, Malkhandi J, et al. Phase I clinical trial of the flavonoid quercetin: Pharmacokinetics and evidence for in vivo tyrosine kinase inhibition. Clin Cancer Res 1996;2:659-67..
  4. Obach RS. Inhibition of human cytochrome P450 enzymes by constituents of St. John's wort, an herbal preparation used in the treatment of depression. J Pharmacol Exp Ther 2000;294:88-95. DOI
  5. Edwards RL, Lyon T, Litwin SE, et al. Quercetin reduces blood pressure in hypertensive subjects. J Nutr 2007;137:2405-11.
  6. Kim KA, Park PW, Kim HK, et al. Effect of quercetin on the pharmacokinetics of rosiglitazone, a CYP2C8 substrate, in healthy subjects. J Clin Pharmacol 2005;45:941-6. PubMed
  7. DiCenzo R, Frerichs V, Larppanichpoonphol P, et al. Effect of quercetin on the plasma and intracellular concentrations of saquinavir in healthy adults. Pharmacotherapy 2006;26:1255-61. PubMed
  8. Choi JS, Choi BC, Choi KE. Effect of quercetin on the pharmacokinetics of oral cyclosporine. Am J Health Syst Pharm 2004;61:2406-9. PubMed
  9. Choi JS, Jo BW, Kim YC. Enhanced paclitaxel bioavailability after oral administration of paclitaxel or prodrug to rats pretreated with quercetin. Eur J Pharm Biopharm 2004;57:313-8. PubMed
  10. Vaclavikova R, Horsky S, Simek P, Gut I. Paclitaxel metabolism in rat and human liver microsomes is inhibited by phenolic antioxidants. Naunyn Schmiedebergs Arch Pharmacol 2003;368:200-9. PubMed
  11. Di Bari L, Ripoli S, Pradhan S, Salvadori P. Interactions between quercetin and warfarin for albumin binding: A new eye on food/drug interference. Chirality 2010;22:593-6. PubMed
  12. Lamson, D. W. and Brignall, M. S. Antioxidants and cancer, part 3: quercetin. Altern.Med.Rev. 2000;5(3):196-208.
  13. Duan KM, Wang SY, Ouyang W, Mao YM, Yang LJ. Effect of quercetin on CYP3A activity in Chinese healthy participants. J Clin Pharmacol 2012;52(6):940-6. PubMed
  14. Wang SY, Duan KM, Li Y, et al. Effect of quercetin on P-glycoprotein transport ability in Chinese healthy subjects. Eur J Clin Nutr 2013;67(4):390-4. PubMed
  15. Nguyen MA, Staubach P, Wolffram S, Langguth P. Effect of single-dose and short-term administration of quercetin on the pharmacokinetics of talinolol in humans - Implications for the evaluation of transporter-mediated flavonoid-drug interactions. Eur J Pha PubMed
  16. Wu LX, Guo CX, Chen WQ, et al. Inhibition of the organic anion-transporting polypeptide 1B1 by quercetin: an in vitro and in vivo assessment. Br J Clin Pharmacol 2012;73(5):750-7.
  17. Ahrens MJ, Thompson DL. Effect of emulin on blood glucose in type 2 diabetics. J Med Food. 2013;16(3):211-5. PubMed
  18. Larson A, Witman MA, Guo Y, et al. Acute, quercetin-induced reductions in blood pressure in hypertensive individuals are not secondary to lower plasma angiotensin-converting enzyme activity or endothelin-1: nitric oxide. Nutr Res. 2012;32(8):557-64. PubMed
  19. Bedada SK, Neerati P. Evaluation of the effect of quercetin treatment on CYP2C9 enzyme activity of diclofenac in healthy human volunteers. Phytother Res. 2018 Feb;32(2):305-311. doi: 10.1002/ptr.5978. PubMed
  20. Zhao Q, Wei J, Zhang H. Effects of quercetin on the pharmacokinetics of losartan and its metabolite EXP3174 in rats. Xenobiotica 2019;49(5):563-8. PubMed
  21. Bhutani P, Rajanna PK, Paul AT. Impact of quercetin on pharmacokinetics of quetiapine: insights from in-vivo studies in wistar rats. Xenobiotica. 2020:1-7.
  22. Li C, Wang X, Bi Y, et al. Potent Inhibitors of Organic Anion Transporters 1 and 3 From Natural Compounds and Their Protective Effect on Aristolochic Acid Nephropathy. Toxicol Sci. 2020;175(2):279-291. PubMed
  23. Ni Y, Duan Z, Zhou D, et al. Identification of Structural Features for the Inhibition of OAT3-Mediated Uptake of Enalaprilat by Selected Drugs and Flavonoids. Front Pharmacol. 2020;11:802. PubMed
  24. Song YK, Yoon JH, Woo JK, et al. Quercetin is a flavonoid breast cancer resistance protein inhibitor with an impact on the oral pharmacokinetics of sulfasalazine in rats. Pharmaceutics 2020;12(5):397. PubMed
  25. Ahmad E, Jahangir M, Ismail MA, et al. Influence of quercetin pretreatment on pharmacokinetics of warfarin in rats. Curr Drug Saf 2022. PubMed
  26. Nambiar A, Kellogg D 3rd, Justice J, et al. Senolytics dasatinib and quercetin in idiopathic pulmonary fibrosis: results of a phase I, single-blind, single-center, randomized, placebo-controlled pilot trial on feasibility and tolerability. EBioMedicine 20 PubMed

See these in context on the Quercetin monograph →

Rutin 2 references
  1. Mehta DK (Ex Ed). British National Formulary, Number 37. British Medical Association and Royal Pharmaceutical Society of Great Britain: London, England, March 1999.
  2. Sun C, Wang L, Sun J, Wang Z, Tang Z. Hypoglycemic and hypolipidemic effects of rutin on hyperglycemic rats. J Tradit Chin Med. 2020;40(4):640-645.

See these in context on the Rutin monograph →

Maritime Pine 14 references
  1. Rice-Evans CA, Packer L, eds. Flavonoids in Health and Disease. Manhattan, NY: Marcel Dekker, Inc., 1998.
  2. Liu FJ, Zhang YX, Lau BH. Pycnogenol enhances immune and haemopoietic functions in senescence-accelerated mice. Cell Mol Life Sci 1998;54:1168-72. PubMed
  3. Putter M, Grotemeyer KH, Wurthwein G, et al. Inhibition of smoking-induced platelet aggregation by aspirin and pycnogenol. Thromb Res 1999;95:155-61. PubMed
  4. Kohama T, Inoue M. Pycnogenol alleviates pain associated with pregnancy. Phytother Res 2006;20:232-4.
  5. Liu X, Zhou HJ, Rohdewald P. French maritime pine bark extract pycnogenol dose-dependently lowers glucose in type 2 diabetic patients (letter). Diabetes Care 2004;27:839. PubMed
  6. Liu X, Wei J, Tan F, et al. Antidiabetic effect of Pycnogenol French maritime pine bark extract in patients with diabetes type II. Life Sci 2004;75:2505-13. PubMed
  7. Wilson D, Evans M, Guthrie N et al. A randomized, double-blind, placebo-controlled exploratory study to evaluate the potential of pycnogenol for improving allergic rhinitis symptoms. Phytother Res 2010;24:1115-9.
  8. Araghi-Niknam, M., Hosseini, S., Larson, D., Rohdewald, P., and Watson, R. R. Pine bark extract reduces platelet aggregation. Integr.Med. 3-21-2000;2(2):73-77. PubMed
  9. Trebaticka, J., Kopasova, S., Hradecna, Z., Cinovsky, K., Skodacek, I., Suba, J., Muchova, J., Zitnanova, I., Waczulikova, I., Rohdewald, P., and Durackova, Z. Treatment of ADHD with French maritime pine bark extract, Pycnogenol. Eur.Child Adolesc.Psychi PubMed
  10. Suzuki, N., Uebaba, K., Kohama, T., Moniwa, N., Kanayama, N., and Koike, K. French maritime pine bark extract significantly lowers the requirement for analgesic medication in dysmenorrhea: a multicenter, randomized, double-blind, placebo-controlled study
  11. Cisar, P., Jany, R., Waczulikova, I., Sumegova, K., Muchova, J., Vojtassak, J., Durackova, Z., Lisy, M., and Rohdewald, P. Effect of pine bark extract (Pycnogenol) on symptoms of knee osteoarthritis. Phytother.Res. 2008;22(8):1087-1092.
  12. Enseleit, F., Sudano, I., Periat, D., Winnik, S., Wolfrum, M., Flammer, A. J., Frohlich, G. M., Kaiser, P., Hirt, A., Haile, S. R., Krasniqi, N., Matter, C. M., Uhlenhut, K., Hogger, P., Neidhart, M., Luscher, T. F., Ruschitzka, F., and Noll, G. Effects
  13. Schoonees, A., Visser, J., Musekiwa, A., and Volmink, J. Pycnogenol(R) (extract of French maritime pine bark) for the treatment of chronic disorders. Cochrane.Database.Syst.Rev. 2012;4:CD008294.
  14. Wang S, Tan D Zhao Y et al. The effect of pycnogenol on the microcirculation, platelet function and ischemic myocardium in patients with coronary artery diseases. Eur Bull Drug Res 1999;7:19-25.

See these in context on the Maritime Pine monograph →

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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

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