Herb & supplement monograph

Indole-3-carbinol Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Indole-3-carbinol interacts with medications. The heart of this page is the interaction list — every drug Indole-3-carbinol is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Indole-3-carbinol is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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On this page

Interaction report

Drugs that interact with Indole-3-carbinol

294 medications have a known interaction with Indole-3-carbinol, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Indole-3-carbinol using our pharmacist-reviewed interaction data.

AI summaries are generated from our Indole-3-carbinol interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Indole-3-carbinol combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Indole-3-carbinol affects

Every type of medication (drug category) Indole-3-carbinol is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 3 drug categories Indole-3-carbinol interacts with

Anticoagulant/antiplatelet DrugsCytochrome P450 1a2 (cyp1a2) SubstratesEstrogens

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

Monograph

Indole-3-carbinol: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

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 effects. Most human evidence is preliminary or comes from lab and animal studies, so it should not be relied on to prevent or treat any disease. Talk to your pharmacist or doctor before using it, and avoid it in pregnancy and breastfeeding.

Family: Brassicaceae
Part used: Derived from glucosinolates found in cruciferous vegetables (broccoli, cabbage, Brussels sprouts, cauliflower)
Common forms: Capsules, tablets, softgels; sometimes combined with or compared to diindolylmethane (DIM)

People commonly use it for

Estrogen and hormone balance support
Breast and cervical health
Prostate health
Antioxidant and 'detox' support
General cancer-prevention interest

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

Likely fine in food amounts, but supplement doses are less studied and should be used cautiously.

PregnancyInsufficient reliable information

There is insufficient reliable information available about the safety of indole-3-carbinol when used during pregnancy and lactation; avoid using.

Read the full pregnancy detail

BreastfeedingInsufficient reliable information

There is insufficient reliable information available about the safety of indole-3-carbinol when used during pregnancy and lactation; avoid using.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Jump to a section

Overview

Indole-3-carbinol (I3C) is a natural compound your body makes when you chew or digest cruciferous vegetables. These include broccoli, cabbage, Brussels sprouts, cauliflower, and kale. The vegetables contain a substance called glucobrassicin, and when the plant cells are broken (by chopping or chewing), it changes into I3C.

As a supplement, I3C is sold in capsules and tablets. People often take it hoping to support hormone balance, breast or prostate health, and the body's natural 'detox' systems. A related compound called diindolylmethane (DIM) forms from I3C in the stomach and is sometimes sold alongside it.

It is important to know that eating these vegetables and taking a concentrated supplement are not the same thing. Supplements give much higher amounts of I3C than a normal diet, and the long-term effects of high doses are not well understood.

How it works

I3C is thought to affect the way the liver breaks down hormones, especially estrogen. In lab studies it appears to shift estrogen breakdown toward forms that some researchers believe may be less harmful, though this is not fully proven in people.

I3C also turns into diindolylmethane (DIM) in the acidic environment of the stomach. Both compounds have been studied in cells for effects on enzymes that process toxins and on signals that control cell growth.

Much of this work is based on laboratory and animal research. What happens in a test tube or in mice does not always carry over to the human body, so these mechanisms should be seen as proposed ideas rather than confirmed facts.

Effectiveness

Does Indole-3-carbinol work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 9 uses evaluated

9 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

For Indole-3-carbinol, current evidence isn’t strong enough to rate any specific use. The conditions it has been studied for are listed below.

Also studied for 9 conditions — evidence insufficient to rate

Insufficient Reliable Evidence To Rate Breast cancer