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Dietary supplement

Estrogen Blocker Ingredients & Drug Interactions

by Iron Brothers Supplements

Estrogen Blocker 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 Estrogen Blocker 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

Estrogen Blocker is a dietary supplement by Iron Brothers Supplements with 4 active ingredients. Its ingredients are commonly taken for low libido and sexual function, athletic performance and muscle building, testosterone support.Based on those ingredients, 1,164 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Bioperine, Grape seed extract, Indole-3-Carbinole. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

Jump to a section

Check Your Meds Against Estrogen Blocker by Iron Brothers Supplements

Ask about any prescription or over-the-counter medication and we check it for interactions with Estrogen Blocker by Iron Brothers Supplements — and tell you which ingredient is responsible.

Pharmacist-reviewed data Checks every ingredient Answer in seconds
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HelloPharmacist Scorecard of Estrogen Blocker by Iron Brothers Supplements

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 4 of its 4 active ingredients.
  • No proprietary blends here — you can verify the dose of every single component.

Estrogen Blocker by Iron Brothers Supplements contains four active ingredients. Tribulus terrestris is a plant extract studied for sexual function.

Bioperine is a black pepper extract that enhances absorption of other compounds. Grape seed extract is a plant-derived antioxidant.

Indole-3-Carbinol is a compound from cruciferous vegetables like broccoli. The product also contains two inactive ingredients: hypromellose (a capsule material) and brown rice flour (a filler).

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: Estrogen and hormone balance support.
  • We looked for evidence on: Breast cancer, Cervical dysplasia, Menopausal symptoms, Polycystic ovary syndrome (PCOS), Premenstrual syndrome (PMS), Hormonal imbalance — and 1 related terms.
  • The closest evidence on file: Tribulus is rated "Insufficient Reliable Evidence To Rate" for Cancer (Natural Medicines).
  • Also on file: Tribulus is rated "Insufficient Reliable Evidence To Rate" for Menopausal symptoms, Polycystic ovary syndrome (PCOS).
  • Also on file: Grape is rated "Insufficient Reliable Evidence To Rate" for Menopausal symptoms, Premenstrual syndrome (PMS).

The evidence for these ingredients varies. Tribulus terrestris is possibly effective for sexual dysfunction, though possibly ineffective for athletic performance, and the evidence for benign prostatic hyperplasia is insufficient to rate.

Black pepper's effectiveness for allergic rhinitis, asthma, athletic performance, headache, depression, and diarrhea is insufficient to rate in our data. Grape seed extract is possibly effective for chronic venous insufficiency (poor circulation in the legs), but possibly ineffective for chemotherapy-related nausea, hay fever, and obesity.

Indole-3-Carbinol's effectiveness for breast cancer, colorectal cancer, cervical dysplasia, liver disease, and fibromyalgia is insufficient to rate.

The evidence, ingredient by ingredient Tribulus Black Pepper Grape Indole-3-carbinol

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 4 of the 4 matched ingredients.
  • Pregnancy & breastfeeding safety ratings cover 4 of 4.
  • General safety write-ups exist for 4 of 4.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Tribulus is often well tolerated short-term in healthy adults, but long-term safety data are limited. Serious side effects are rare but include liver and kidney injury and seizures.

Gastrointestinal complaints like abdominal pain, nausea, and diarrhea occur, though one study found these occurred at rates similar to placebo. Avoid tribulus during pregnancy because it may affect hormones and safety is not established; also avoid while breastfeeding due to lack of reliable safety information.

Black pepper in food amounts is generally safe, but concentrated supplements should be used cautiously. Common side effects are burning aftertaste and indigestion.

Serious allergic reactions are rare. Grape seed extract appears generally well tolerated, with the most common effects being abdominal pain, diarrhea, and headache.

Serious allergic reactions are rare. Grape seed extract is likely safe during pregnancy in normal food amounts, but concentrated supplements are not well studied.

Safety while breastfeeding is not established. Indole-3-Carbinol is likely fine in food amounts but is less studied at supplement doses.

Common side effects are diarrhea, nausea, and rash; unsteadiness and tremor have been reported, especially at higher doses. Avoid concentrated supplements during pregnancy and breastfeeding due to insufficient safety data and possible hormone effects.

Side effects, ingredient by ingredient Tribulus Black Pepper Grape Indole-3-carbinol

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?
  • 4 of the 4 matched ingredients can interact with medications — Tribulus, Grape, Black Pepper, Indole-3-carbinol.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs; immunosuppressants / transplant drugs; diabetes medications; lithium.
  • For scale: 1,165 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 this product, check with your pharmacist if you take estrogen therapy (Moderate severity — this product may interfere with it), blood pressure medications, diabetes medications, lithium, any specific medications metabolized by your liver, blood thinners or antiplatelet drugs, or theophylline, propranolol, phenytoin, rifampin, cyclosporine, nevirapine, atorvastatin, or pentobarbital. Altogether, these interactions span 1,149 individual medications.

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. Moderate medication interactions have been identified, and safety information is well characterized.

This product is designed for those interested in supporting hormonal health, but it carries multiple medication interactions across a very wide range of drugs. If you take any prescription medication — blood pressure drugs, diabetes medications, mood stabilizers, heart or seizure medications, blood thinners, or any others — talk with your pharmacist before starting.

The individual ingredients are generally well tolerated, but long-term safety data are limited.

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

Assessment coverage: 4 of 4 active ingredients matched to our full ingredient reviews (monographs). Based on the product label dated May 19, 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 Estrogen Blocker, straight from the product label.

Brand Iron Brothers Supplements
Barcode (UPC) X001RVGBZF
Net contents 60 Capsule(s)
Market status On market
Date entered into DSLD May 19, 2022
DSLD ID 263521
Product type Other Combinations
Supplement form Capsule
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Adult (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 Estrogen Blocker by Iron Brothers Supplements, 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:
2 Capsule(s)
Maximum serving Sizes:
2 Capsule(s)
Servings per container
30
UPC/BARCODE
X001RVGBZF
IngredientAmount% DV
Tribulus terrestris300 mg--
Bioperine5 mg--
Grape seed extract150 mg--
Indole-3-Carbinole75 mg--

Other ingredients: Hypromellose, Brown Rice Flour

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.
Suggested/Recommended/Usage/Directions

Directions Take (2) capsules daily with food. Do not exceed 8 weeks of continuous use without a 4 week off period.

Precautions

Warnings Not for use of persons under the age of 18. Keep out of reach of children.

Consult your doctor prior to use if you have any medical conditions or if you are taking any other medications.

Discontinue use immediately if you experience rapid heartbeat, dizziness, vomiting or other similar symptoms. Do not use if safety seal is damaged or missing.

Storage

Store in a cool, dry place.

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)

BioPerine is a registered trademark of Sabinsa Corporation

Grit guts glory

General Statements

Visit us online www.ironbrothers.com

Transparent ingredients Full label disclosure

Formulation

Testosterone booster Lean muscle support Test boost

FDA Statement of Identity

Dietary Supplement

Seals/Symbols

GMP Compliant Good Manufacturing Practice Made in the U.S.A.

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

See for yourself

Estrogen Blocker by Iron Brothers Supplements label

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

Estrogen Blocker 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 Estrogen Blocker by Iron Brothers Supplements

These are the 4 active ingredients this product is made of. Select any to open its full monograph.

Serving size2 Capsule(s) Dosage formCapsule Servings per container30 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.

Tribulus terrestris

Interacts with
259 drugs
300 mg per serving Form: Saponins

Tribulus is a plant supplement most often marketed to boost libido, testosterone, and athletic performance, but the human evidence behind these claims...

Tribulus terrestris monograph & interactions

Bioperine

Interacts with
1,019 drugs
5 mg per serving Form: Black Pepper fruit extract

Black pepper is a common kitchen spice that is generally safe in the amounts used in food. Its extract, piperine, is mostly added to supplements to he...

Bioperine monograph & interactions

Grape seed extract

Interacts with
910 drugs
150 mg per serving Form: Proanthocyanidins

Grapes and grape products like grape seed extract contain antioxidant compounds such as resveratrol and proanthocyanidins that may support heart and b...

Grape seed extract monograph & interactions

Indole-3-Carbinole

Interacts with
294 drugs
75 mg per serving

Indole-3-carbinol (I3C) is a compound formed when you eat cruciferous vegetables like broccoli and cabbage, and it is sold as a supplement mainly for...

Indole-3-Carbinole monograph & interactions

Other (inactive) ingredients: Hypromellose, Brown Rice Flour. These complete the product’s ingredient list but are not active constituents.

Interaction report

Estrogen Blocker by Iron Brothers Supplements Drug Interactions

Want to check YOUR meds against Estrogen Blocker?

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
1,164Drugs
1,145 Moderate 19 Minor

Ingredients driving the most interactions

Bioperine 1,019
Grape seed extract 910
Indole-3-Carbinole 294
Tribulus terrestris 259

Individual Drug Interactions

The ingredients in Estrogen Blocker interact with 1,164 drugs. Click any drug to see the details.

4 of the 4 ingredients in Estrogen Blocker interact with drugs. Each result below shows which ingredient is responsible. Bioperine Grape seed extract Indole-3-Carbinole Tribulus terrestris

Each ingredient & the kinds of drugs it affects

For each ingredient in Estrogen Blocker 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.

Bioperine17 drug types · 1,019 drugs

Anticoagulant/Antiplatelet Drugs

Theoretically, black pepper might increase the risk of bleeding when taken with antiplatelet or anticoagulant drugs.
In vitro research shows that piperine, a constituent of black pepper, seems to inhibit platelet aggregation. This has not been reported in humans.

Likelihood Possible Evidence D
Antidiabetes Drugs

Theoretically, black pepper might increase the risk of hypoglycemia when taken with antidiabetes drugs.
Animal research shows that piperine, a constituent of black pepper, can reduce blood glucose levels. Monitor blood glucose levels closely. Dose adjustments might be necessary.

Likelihood Possible Evidence D
Atorvastatin (Lipitor)

Theoretically, black pepper might increase blood levels of atorvastatin.
Animal research shows that taking piperine, a constituent of black pepper, 35 mg/kg can increase the maximum serum concentration of atorvastatin three-fold. This has not been reported in humans.

Likelihood Possible Evidence D
Cyclosporine (Neoral, Sandimmune)

Theoretically, black pepper might increase the effects and side effects of cyclosporine.
In vitro research shows that piperine, a constituent of black pepper, increases the bioavailability of cyclosporine. This has not been reported in humans.

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

Theoretically, black pepper might increase levels of drugs metabolized by CYP2D6.
In vitro research suggests that some constituents of black pepper inhibit CYP2D6. This has not been reported in humans.

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

Theoretically, black pepper might increase levels of drugs metabolized by CYP3A4.
In vitro research and pharmacokinetic simulation data suggest that piperine, a constituent of black pepper, as well as the pepper fruit seem to inhibit CYP3A4. This has not been reported in humans.

Likelihood Possible Evidence D
Lithium

Theoretically, black pepper might increase blood levels of lithium due to its diuretic effects. The dose of lithium might need to be reduced.
Black pepper is thought to have diuretic properties.

Likelihood Probable Evidence D
Nevirapine (Viramune)

Black pepper might increase blood levels of nevirapine.
Clinical research shows that piperine, a constituent of black pepper, increases the plasma concentration of nevirapine. However, no adverse effects were observed in this study.

Likelihood Probable Evidence D
P-Glycoprotein Substrates

Theoretically, black pepper might increase levels of P-glycoprotein substrates.
In vitro research shows that piperine, a constituent of black pepper, seems to inhibit P-glycoprotein.

Likelihood Possible Evidence D
Pentobarbital (Nembutal)

Theoretically, black pepper might increase the sedative effects of pentobarbital.
Animal research shows that piperine, a constituent of black pepper, increases pentobarbital-induced sleeping time.

Likelihood Possible Evidence D
Phenytoin (Dilantin)

Black pepper might increase blood levels of phenytoin.
Clinical research shows that piperine, a constituent of black pepper, seems to increase absorption, slow elimination, and increase levels of phenytoin. Taking a single dose of black pepper 1 gram along with phenytoin seems to double the serum concentration of phenytoin. Consuming a soup with black pepper providing piperine 44 mg/200 mL of soup along with phenytoin also seems to increase phenytoin levels when compared with consuming the same soup without black pepper.

Likelihood Possible Evidence B
Propranolol (Inderal)

Black pepper might increase blood levels of propranolol.
Clinical research shows that piperine, a constituent of black pepper, seems to increase absorption and slow elimination of propranolol.

Likelihood Possible Evidence B
Rifampin (Rifadin)

Black pepper might increase blood levels of rifampin.
Clinical research shows that piperine, a constituent of black pepper, seems to increase absorption and serum levels of rifampin.

Likelihood Possible Evidence B
Theophylline

Black pepper might increase blood levels of theophylline.
Clinical research shows that piperine, a constituent of black pepper, seems to increase absorption and slow elimination of theophylline.

Likelihood Possible Evidence D
Amoxicillin (Amoxil, Trimox)

Theoretically, black pepper might increase the effects and side effects of amoxicillin.
Animal research shows that taking piperine, a constituent of black pepper, with amoxicillin increases plasma levels of amoxicillin. This has not been reported in humans.

Likelihood Possible Evidence D
Carbamazepine (Tegretol)

Theoretically, black pepper might increase blood levels of carbamazepine, potentially increasing the effects and side effects of carbamazepine.
One clinical study in patients taking carbamazepine 300 mg or 500 mg twice daily shows that taking a single 20 mg dose of purified piperine, a constituent of black pepper, increases carbamazepine levels. Piperine may increase carbamazepine absorption by increasing blood flow to the GI tract, increasing the surface area of the small intestine, or inhibiting cytochrome P450 3A4 (CYP3A4) in the gut wall. Absorption was significantly increased by 7-10 mcg/mL/hour. The time to eliminate carbamazepine was also increased by 4-8 hours. Although carbamazepine levels were increased, this did not appear to increase side effects. In vitro research also shows that piperine can increase carbamazepine levels by 11% in a time-dependent manner.

Likelihood Possible Evidence B
Cytochrome P450 1A2 (Cyp1A2) Substrates

Theoretically, black pepper might decrease levels and clinical effects of drugs metabolized by CYP1A2.
In vitro research suggests that black pepper induces CYP1A2. This has not been reported in humans.

Likelihood Possible Evidence D
Bioperine full monograph & interactions

Grape seed extract9 drug types · 910 drugs

Anticoagulant/Antiplatelet Drugs

Theoretically, grape extracts may have antiplatelet effects and may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
In vitro evidence suggests that grape extracts might decrease platelet aggregation.

Likelihood Possible Evidence D
Cyclosporine (Neoral, Sandimmune)

Ingesting grape juice with cyclosporine can reduce cyclosporine absorption.
A small pharmacokinetic study in healthy young adults shows that intake of purple grape juice 200 mL along with cyclosporine can decrease the absorption of cyclosporine by up to 30% when compared with water. Separate doses of grape juice and cyclosporine by at least 2 hours to avoid this interaction.

Likelihood Possible Evidence B
Cytochrome P450 1A2 (Cyp1A2) Substrates

Theoretically, grape juice might reduce the levels of CYP1A2 substrates.
A small pharmacokinetic study in healthy adults shows that ingestion of 200 mL of grape juice decreases phenacetin plasma levels. This is thought to be due to induction of CYP1A2.

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

Theoretically, grape seed extract may increase the levels of CYP2D6 substrates.
In vitro evidence suggests that grape seed extract might inhibit CYP2D6 enzymes. However, this interaction has not been reported in humans.

Likelihood Possible Evidence D
Cytochrome P450 2E1 (Cyp2E1) Substrates

Theoretically, grape seed extract might increase the levels of CYP2E1 substrates.
In vitro and animal research suggests that grape seed proanthocyanidin extract inhibits CYP2E1 enzymes. However, this interaction has not been reported in humans.

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

It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
In vitro evidence suggests that grape seed extract might inhibit CYP3A4 enzymes. However, evidence from animal research shows that grape seed extract may induce CYP3A4 in the liver. So far, these interactions have not been reported in humans.

Likelihood Possible Evidence D
Midazolam (Versed)

Theoretically, long-term intake of grape seed extract might decrease the effects of midazolam.
Animal research shows that subchronic ingestions of grape seed extract can increase the elimination of intravenous midazolam by increasing hepatic CYP3A4 activity. Single doses of grape seed extract do not appear to affect midazolam elimination.

Likelihood Possible Evidence D
Phenacetin

Grape juice might decrease phenacetin absorption.
A small pharmacokinetic study in healthy adults shows that ingestion of 200 mL of grape juice decreases phenacetin plasma levels. This is thought to be due to induction of cytochrome P450 1A2 (CYP1A2).

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

It is unclear if grape juice or grape seed extract inhibits CYP2C9; research is conflicting.
In vitro evidence shows that grape seed extract or grape juice might inhibit CYP2C9 enzymes. However, a small pharmacokinetic study in healthy adults shows that drinking 8 ounces of grape juice once does not affect the clearance of flurbiprofen, a probe-drug for CYP2C9 metabolism. The effects of continued grape juice consumption are unclear.

Likelihood Unlikely Evidence D
Grape seed extract full monograph & interactions

Indole-3-Carbinole3 drug types · 294 drugs

Anticoagulant/Antiplatelet Drugs

Theoretically, indole-3-carbinol might increase the risk of bleeding when used with antiplatelet or anticoagulant drugs.
In vitro research shows that indole-3-carbinol inhibits platelet aggregation.

Likelihood Possible Evidence D
Cytochrome P450 1A2 (Cyp1A2) Substrates

Theoretically, indole-3-carbinol might increase the metabolism of CYP1A2 substrates and lower serum concentrations.
Animal research shows that indole-3-carbinol induces CYP1A2 enzymes.

Likelihood Possible Evidence D
Estrogens

Indole-3-carbinol might interfere with the effects of estrogen therapy.
Preliminary clinical and in vitro evidence shows that indole-3-carbinol has antiestrogenic activity.

Likelihood Possible Evidence D
Indole-3-Carbinole full monograph & interactions

Tribulus terrestris3 drug types · 259 drugs

Antidiabetes Drugs

Taking tribulus with antidiabetes drugs might increase the risk of hypoglycemia.
Clinical research shows that Tribulus can lower blood glucose levels in adults with type 2 diabetes who are taking antidiabetes medications.

Likelihood Possible Evidence D
Antihypertensive Drugs

Theoretically, taking tribulus with antihypertensive drugs might increase the risk of hypotension.
Animal research shows that tribulus can lower blood pressure by inhibiting angiotensin-converting enzyme (ACE). Tribulus has also demonstrated hypotensive effects in pre-hypertensive adults.

Likelihood Possible Evidence D
Lithium

Theoretically, tribulus might increase the levels and clinical effects of lithium.
Tribulus is thought to have diuretic properties. Due to these potential diuretic effects, tribulus might reduce excretion and increase levels of lithium. The dose of lithium might need to be decreased.

Likelihood Probable Evidence D
Tribulus terrestris full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Estrogen Blocker, from the product label.

Iron Brothers Supplements

See all Iron Brothers Supplements products
Name
Iron Brothers LLC
Street Address
848 N. Rainbow Blvd. #2711
City
Las Vegas
State
NV
ZipCode
89107
Web Address
www.IronBrothers.com
Pharmacist Counseling Corner

Estrogen Blocker by Iron Brothers Supplements: Common Questions

Does Estrogen Blocker by Iron Brothers Supplements interact with any medications?
Yes. Based on its ingredients, Estrogen Blocker has a known interaction with 1,164 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Estrogen Blocker contains 4 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.
Is this product safe during pregnancy?
No. Tribulus and Indole-3-Carbinol should be avoided during pregnancy because safety is not established and they may affect hormones. Grape seed extract in food amounts is likely safe, but concentrated supplements are not well studied. Talk with your doctor or pharmacist for personalized advice before using any of these ingredients while pregnant.
Is this product safe while breastfeeding?
Tribulus and Indole-3-Carbinol should be avoided while breastfeeding due to lack of reliable safety information. Grape seed extract's safety while breastfeeding is not established. Talk with your doctor or pharmacist before using while breastfeeding.
What are the most common side effects?
Common side effects vary by ingredient. Tribulus may cause abdominal pain, nausea, diarrhea, or constipation, though one study found these occurred at rates similar to placebo. Black pepper may cause a burning aftertaste or indigestion. Grape seed extract may cause abdominal pain, diarrhea, dry mouth, or headache. Indole-3-Carbinol may cause diarrhea, nausea, or rash.
Does this product actually block estrogen?
The evidence in our data doesn't establish effectiveness for any condition. Indole-3-Carbinol shows antiestrogenic activity in preliminary research, but whether this translates to real benefit is insufficient to rate in the data we hold.
Can I take this if I'm on blood thinners?
No — at least not without talking to your pharmacist first. Both grape seed extract and Indole-3-Carbinol interact with blood thinners and antiplatelet drugs (Moderate severity), potentially increasing bleeding risk. Check with your pharmacist before starting.
How long until this product works?
The effectiveness data in our facts don't address timing or how long results take. Talk with your pharmacist or the product manufacturer about realistic expectations.

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.

Estrogen Blocker label
Go deeper

The Full Monographs Behind Estrogen Blocker’s Ingredients

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

Herb & supplement monograph

Tribulus

Interacts with 259 drugs

Tribulus is a plant supplement most often marketed to boost libido, testosterone, and athletic performance, but the human evidence behind these claims is weak and inconsistent. It is general...

Read the full Tribulus monograph → Herb & supplement monograph

Black Pepper

Interacts with 1,019 drugs

Black pepper is a common kitchen spice that is generally safe in the amounts used in food. Its extract, piperine, is mostly added to supplements to help the body absorb other ingredients (li...

Read the full Black Pepper monograph → Herb & supplement monograph

Grape

Interacts with 910 drugs

Grapes and grape products like grape seed extract contain antioxidant compounds such as resveratrol and proanthocyanidins that may support heart and blood vessel health. While the food is he...

Read the full Grape monograph → Herb & supplement monograph

Indole-3-carbinol

Interacts with 294 drugs

Indole-3-carbinol (I3C) is a compound formed when you eat cruciferous vegetables like broccoli and cabbage, and it is sold as a supplement mainly for hormone-related and cell-protective effe...

Read the full Indole-3-carbinol monograph →
Sources

Sources & How We Checked

Estrogen Blocker'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 82 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.

Tribulus 10 references
  1. Sharifi AM, Darabi R, Akbarloo N. Study of antihypertensive mechanism of Tribulus terrestris in 2K1C hypertensive rats: role of tissue ACE activity. Life Sci 2003;73:2963-71. PubMed
  2. Walker D, Bird A, Flora T, O'Sullivan B. Some effects of feeding Tribulus terrestris, Ipomoea lonchophylla and the seed of Abelmoschus ficulneus on fetal development and the outcome of pregnancy in sheep. Reprod Fertil Dev 1992;4:135-44. PubMed
  3. Al-Ali M, Wahbi S, Twaij H, Al-Badr A. Tribulus terrestris: preliminary study of its diuretic and contractile effects and comparison with Zea mays. J Ethnopharmacol 2003;85:257-60. PubMed
  4. Tabakova, P., Dimitrov, M., Ognyanov, K., and et al. Clinical study of Tribestan in females with endocrine sterility. Documentation for Registration (unpublished) 1999.
  5. Akhtari E, Raisi F, Keshavarz M, et al. Tribulus terrestris for treatment of sexual dysfunction in women: randomized double-blind placebo-controlled study. Daru 2014;22:40. PubMed
  6. Ryan M, Lazar I, Nadasdy GM, et al. Acute kidney injury and hyperbilirubinemia in a young male after ingestion of Tribulus terrestris. Clin Nephrol 2015;83(3):177-83. PubMed
  7. Postigo S, Lima SM, Yamada SS, et al. Assessment of the effects of Tribulus terrestris on sexual function of menopausal women. Rev Bras Ginecol Obstet 2016;38(3):140-6. PubMed
  8. Talasaz AH, Abbasi MR, Abkhiz S, Dashti-Khavidaki S. Tribulus terrestris-induced severe nephrotoxicity in a young healthy male. Nephrol Dial Tranplant 2010;25(11):3792-3. PubMed
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Black Pepper 29 references
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Grape 34 references
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Indole-3-carbinol 9 references
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