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Dietary supplement

Soy Isoflavones Ingredients & Drug Interactions

by Life Extension

Soy Isoflavones label
See full label image
Capsule Category: Non-nutrient/non-botanical
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 23, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Soy Isoflavones 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

Soy Isoflavones is a dietary supplement by Life Extension with 1 active ingredient. Its ingredients are commonly taken for alcohol cravings and reduction, menopausal symptoms, heart and blood vessel health.Based on those ingredients, 584 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Isoflavones. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against Soy Isoflavones by Life Extension

Ask about any prescription or over-the-counter medication and we check it for interactions with Soy Isoflavones by Life Extension — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of Soy Isoflavones by Life Extension

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 11, 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 1 of its 1 active ingredient.
  • “NovaSoy” is listed as a grouped ingredient — the label gives one combined amount (135 mg) without saying how much of each component you get.

This product contains one active ingredient: isoflavones sourced from kudzu. Isoflavones are plant compounds with estrogenic properties — meaning they can mimic or interact with estrogen in your body.

The product also contains several inactive ingredients (cellulose, ascorbyl palmitate, and silica), which are fillers and stabilizers.

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

This product doesn't appear to be marketed for a specific use, so we graded Kudzu's overall clinical evidence instead.

Moderate

Some clinical evidence supports Kudzu for:

Why this rating?
  • We looked at the product name, claims, and label statements and couldn't find a stated purpose to grade.
  • Since the label doesn't commit to one use, we graded the ingredient's overall clinical evidence instead.
  • On file: Alcohol use disorder — rated "Possibly Effective" (Natural Medicines).

The evidence for kudzu isoflavones is mixed. For alcohol use disorder, there's possibly effective evidence — meaning some research supports it, but more confirmation is needed.

For hay fever (allergic rhinitis), angina, and back pain, there isn't enough reliable evidence in our data to say whether it works or doesn't.

The evidence, ingredient by ingredient Kudzu

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 1 of the 1 matched ingredient.
  • Pregnancy & breastfeeding safety ratings cover 1 of 1.
  • General safety write-ups exist for 1 of 1.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

In short-term clinical trials, kudzu was generally well tolerated. The side effects reported — nausea, indigestion, bloating, rash, and dizziness — occurred no more often than with placebo.

However, long-term safety data isn't well established, so we don't know what happens with extended use. Due to its possible hormone-like effects and lack of safety data, the evidence advises against use during pregnancy or breastfeeding.

If you're pregnant, nursing, or planning either, talk with your doctor or pharmacist before taking this product.

Side effects, ingredient by ingredient Kudzu

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?
  • 1 of the 1 matched ingredient can interact with medications — Kudzu.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs; diabetes medications.
  • For scale: 585 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 you take this, double-check if you're on blood thinners or antiplatelet drugs (like warfarin, apixaban, aspirin, or clopidogrel) — kudzu may increase bleeding risk. Also flag any use of estrogen therapy, methotrexate, tamoxifen, hepatotoxic (liver-stressing) drugs, caffeine supplements or heavy caffeine use, or diabetes medications with your pharmacist.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with some supporting evidence behind its ingredients' uses. Moderate medication interactions have been identified, and safety information is well characterized.

This supplement may be worth considering if you're looking at alcohol use disorder support and have no interactions with medications. But if you take blood thinners, estrogen, methotrexate, tamoxifen, diabetes medications, or use caffeine regularly, you need to check with your pharmacist first — the interactions are real.

Pregnant and breastfeeding folks should skip it. Talk to us before starting.

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

Assessment coverage: 1 of 1 active ingredient matched to our full ingredient reviews (monographs). Based on the product label dated Apr 24, 2025.

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 Soy Isoflavones, straight from the product label.

Brand Life Extension
Barcode (UPC) 737870164968
Net contents 30 Vegetarian Capsule(s)
Market status On market
Date entered into DSLD Apr 24, 2025
DSLD ID 328715
Product type Non-nutrient/non-botanical
Supplement form Capsule
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years), Post-Menopause, Seniors/Mature (>50 Years) - Women ONLY, Gluten 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 Soy Isoflavones by Life Extension, 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 Vegetable Capsule(s)
Maximum serving Sizes:
1 Vegetable Capsule(s)
Servings per container
30
UPC/BARCODE
737870164968
IngredientAmount% DV
Isoflavones54 mg--
NovaSoy135 mg--

Other ingredients: Cellulose, Ascorbyl Palmitate, Silica

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.
General Statements

Scan for product info

Typical soy isoflavone profile: Genistein and its precursor isoform genistin: 28 mg Daidzein and its precursor isoform daidzin: 22 mg Glycitein and its precursor isoform glycitin: 4 mg

Precautions

Read the entire label and follow the directions carefully.

Warnings: Keep out of reach of children.

Do not exceed recommended dose. Do not purchase if outer seal is damaged.

Consult with your physician if you are undergoing treatment for a medical condition or if you are pregnant or lactating.

Contains soybeans.

To report a serious adverse event or obtain product information, contact 1-866-280-2852.

Suggested/Recommended/Usage/Directions

Directions: Take one (1) capsule once or twice daily, or as recommended by a healthcare practitioner.

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.

Brand IP Statement(s)

Novasoy and the Novasoy logo are registered trademarks of Archer-Daniels-Midland Company.

Formulation

Gluten free Non GMO Le certified

Supports postmenopausal bone & cardiovascular health

Seals/Symbols

Non GMO Le certified

Formula

Novasoy Brand Soy Isoflavones

FDA Statement of Identity

Dietary Supplement

Storage

Store tightly closed in a cool, dry place.

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

See for yourself

Soy Isoflavones by Life Extension label

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

Soy Isoflavones 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 Soy Isoflavones by Life Extension

This is the 1 active ingredient this product is made of. Select it to open its full monograph.

Serving size1 Vegetable Capsule(s) Dosage formCapsule Servings per container30 Amounts shown are per serving.

NovaSoy

135 mg per serving Form: Soy Isoflavones Concentrate

Other (inactive) ingredients: Cellulose, Ascorbyl Palmitate, Silica. These complete the product’s ingredient list but are not active constituents.

Interaction report

Soy Isoflavones by Life Extension Drug Interactions

Want to check YOUR meds against Soy Isoflavones?

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
584Drugs
512 Moderate 72 Minor

Ingredients driving the most interactions

Isoflavones 584

Individual Drug Interactions

The ingredients in Soy Isoflavones interact with 584 drugs. Click any drug to see the details.

1 of the 1 ingredient in Soy Isoflavones interact with drugs. Each result below shows which ingredient is responsible. Isoflavones

Each ingredient & the kinds of drugs it affects

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

Isoflavones7 drug types · 584 drugs

Anticoagulant/Antiplatelet Drugs

Theoretically, kudzu may increase the risk of bleeding if used with antiplatelet or anticoagulant drugs.
Kudzu isoflavones are reported to have antiplatelet activity.

Likelihood Possible Evidence D
Caffeine

Theoretically, taking kudzu with caffeine might increase levels of caffeine.
In healthy males injected with the kudzu constituent puerarin, caffeine clearance and metabolism is inhibited. This effect has been attributed to inhibition of cytochrome P450 1A2 (CYP1A2) enzyme, which is involved in caffeine metabolism. It is unclear if taking kudzu orally would have this same effect.

Likelihood Probable Evidence D
Estrogens

Theoretically, kudzu might alter the effects of estrogen therapy.
Some research suggests that kudzu has estrogenic effects. This may enhance or inhibit the effects of estrogen therapy.

Likelihood Possible Evidence B
Hepatotoxic Drugs

Theoretically, concomitant use might have additive hepatotoxic effects.
There is some concern that kudzu can adversely affect the liver.

Likelihood Possible Evidence D
Methotrexate (Trexall, Others)

Theoretically, taking kudzu with methotrexate might increase the risk of methotrexate toxicity.
Preclinical research suggests that kudzu extract greatly reduces the elimination and increases the toxicity of methotrexate. Kudzu might inhibit organic anion transporters (OATs) that are responsible for hepatobiliary and renal excretion of anions, similar to the interaction between methotrexate and non-steroidal anti-inflammatory drugs (NSAIDs).

Likelihood Possible Evidence D
Tamoxifen (Nolvadex)

Theoretically, kudzu might interfere with tamoxifen activity.
Some research suggests that kudzu may have estrogenic effects.

Likelihood Possible Evidence B
Antidiabetes Drugs

Theoretically, taking kudzu with antidiabetes drugs might increase the risk of hypoglycemia.
Kudzu might lower blood glucose levels and have additive effects in patients treated with antidiabetic agents. The dose of diabetes medications might need to be adjusted.

Likelihood Unlikely Evidence D
Isoflavones full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Soy Isoflavones, from the product label.

Life Extension

See all Life Extension products
Name
Quality Supplements and Vitamins, Inc.
City
Ft. Lauderdale
State
FL
ZipCode
33309
Phone Number
1-866-280-2852
Web Address
LifeExtension.com
Pharmacist Counseling Corner

Soy Isoflavones by Life Extension: Common Questions

Does Soy Isoflavones by Life Extension interact with any medications?
Yes. Based on its ingredients, Soy Isoflavones has a known interaction with 584 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Soy Isoflavones contains a single active ingredient, and that one ingredient can interact with many different medications on its own. We check it against each medication and show the mechanism 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.
What are isoflavones and why are they in this product?
Isoflavones are plant compounds with estrogenic properties — they can mimic estrogen in your body. This product contains them from kudzu because some research suggests they may help with alcohol use disorder.
Can I take this while I'm pregnant or breastfeeding?
No. There isn't enough safety data, and kudzu's hormone-like effects raise concerns during pregnancy and nursing. Talk with your doctor or pharmacist if you're considering it while pregnant or breastfeeding.
What side effects might I notice?
In clinical trials, some people reported nausea, indigestion, bloating, rash, or dizziness — but these effects didn't happen more often than with placebo. Long-term side effects aren't well studied yet.
Does this supplement really work?
For alcohol use disorder, there's some research suggesting it may help (possibly effective). For hay fever, angina, or back pain, we don't have enough reliable evidence to say one way or the other.
What should I know about long-term use?
Short-term safety looks okay, but long-term safety data isn't well established. If you're planning to take this regularly, talk with your pharmacist about monitoring.

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

Not sure if Soy Isoflavones is safe with your meds?

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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.

Soy Isoflavones label
Go deeper

The Full Monographs Behind Soy Isoflavones’s Ingredients

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

Herb & supplement monograph

Kudzu

Interacts with 584 drugs

Kudzu is a fast-growing vine whose root has long been used in traditional Chinese medicine and is now studied mostly for reducing alcohol intake. Early research is promising for cutting back...

Read the full Kudzu monograph →
Sources

Sources & How We Checked

Soy Isoflavones'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 21 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.

Kudzu 21 references
  1. Woo J, Lau E, Ho SC, et al. Comparison of Pueraria lobata with hormone replacement therapy in treating the adverse health consequences of menopause. Menopause 2003;10:352-61. PubMed
  2. Akita H, Sowa J, Makiura M, et al. Maculopapular drug eruption due to the Japanese herbal medicine Kakkonto (kudzu or arrowroot decoction). Contact Dermatitis 2003;48:348-9. PubMed
  3. Luo ZR, Zheng B. [Effect of Puerarin on platelet activating factors CD63 and CD62P, plasminogen activator inhibitor and C-reactive protein in patients with unstable angia pectoris]. Zhongguo Zhong Xi Yi Jie He Za Zhi 2001;21:31-3 .
  4. Lee KT, Sohn IC, Kim DH, et al. Hypoglycemic and hypolipidemic effects of tectorigenin and kaikasaponin III in the streptozotocin-lnduced diabetic rat and their antioxidant activity in vitro. Arch Pharm Res 2000;23:461-6.
  5. Yu Z, Zhang G, Zhao H. [Effects of Puerariae isoflavone on blood viscosity, thrombosis and platelet function]. Zhong Yao Cai 1997;20:468-9.
  6. Hsu FL, Liu IM, Kuo DH, et al. Antihyperglycemic effect of puerarin in streptozotocin-induced diabetic rats. J Nat Prod 2003;66:788-92. PubMed
  7. Chiang HM, Fang SH, Wen KC, et al. Life-threatening interaction between the root extract of Pueraria lobata and methotrexate in rats. Toxicol Appl Pharmacol 2005;209:263-8.
  8. Zheng, J., Chen, B., Jiang, B., Zeng, L., Tang, Z. R., Fan, L., and Zhou, H. H. The effects of puerarin on CYP2D6 and CYP1A2 activities in vivo. Arch Pharm Res 2010;33(2):243-246. PubMed
  9. Hsu, H. H., Chang, C. K., Su, H. C., Liu, I. M., and Cheng, J. T. Stimulatory effect of puerarin on alpha1A-adrenoceptor to increase glucose uptake into cultured C2C12 cells of mice. Planta Med 2002;68(11):999-1003.
  10. Zheng, G., Zhang, X., Zheng, J., Meng, Q., and Zheng, D. [Estrogen-like effects of puerarin and total isoflavones from Pueraria lobata]. Zhong.Yao Cai. 2002;25(8):566-568.
  11. Qi, B. L. and Qi, B. M. [Effect of the purariae-isofiavones on estrogen level in normal and ovariectomized rats]. Zhongguo Zhong.Yao Za Zhi. 2002;27(11):850-852.
  12. Akita, H., Sowa, J., Makiura, M., Akamatsu, H., and Matsunaga, K. Maculopapular drug eruption due to the Japanese herbal medicine Kakkonto (kudzu or arrowroot decoction). Contact Dermatitis 2003;48(6):348-349. PubMed
  13. Manonai, J., Chittacharoen, A., Theppisai, U., and Theppisai, H. Effect of Pueraria mirifica on vaginal health. Menopause. 2007;14(5):919-924. PubMed
  14. Chandeying, V. and Sangthawan, M. Efficacy comparison of Pueraria mirifica (PM) against conjugated equine estrogen (CEE) with/without medroxyprogesterone acetate (MPA) in the treatment of climacteric symptoms in perimenopausal women: phase III study. J M
  15. Virojchaiwong, P., Suvithayasiri, V., and Itharat, A. Comparison of Pueraria mirifica 25 and 50 mg for menopausal symptoms. Arch.Gynecol.Obstet. 2011;284(2):411-419. PubMed
  16. Hou, Q., Ao, X., Li, G., and Zhang, Y. [Puerarin combined with avandia for diabetic nephropathy]. Zhong.Nan.Da.Xue Xue Bao Yi Xue Ban. 2012;37(1):73-77.
  17. Kim HJ, Kim H, Ahn JH, Suk JH. Liver injury induced by herbal extracts containing mistletoe and kudzu. J Altern Complement Med 2015;21(3):180-5. PubMed
  18. Santosh N, Mohan K, Royana S, Yamini TB. Hepatotoxicity of tubers of Indian Kudzu (Pueraria tuberosa) in rats. Food Chem Toxicol. 2010 Apr;48(4):1066-71. PubMed
  19. Teschke R, Zhang L, Long H, Schwarzenboeck A, Schmidt-Taenzer W, Genthner A, Wolff A, Frenzel C, Schulze J, Eickhoff A. Traditional Chinese Medicine and herbal hepatotoxicity: a tabular compilation of reported cases. Ann Hepatol. 2015 Jan-Feb;14(1):7-19. DOI
  20. Wang D, Qiu L, Wu X, Wei H, Xu F. Evaluation of kudzu root extract-induced hepatotoxicity. J Ethnopharmacol. 2015 Dec 24;176:321-6. PubMed
  21. Warinsiriruk P, Tantitham C, Cherdshewasart W, Shobeiri SA, Manonai J. Effects of Pueraria mirifica on vaginal artery vascularization in postmenopausal women with genitourinary syndrome of menopause. Maturitas 2022;160:4-10. PubMed

See these in context on the Kudzu 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

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