Indole-3‑Carbinol Dosage: How to Start and Stay Safe

Eating broccoli won’t get you the doses used in supplement studies — you’d need a lot of vegetables to match a single pill. Indole-3‑carbinol (I3C) comes from cruciferous veggies and is sold as a supplement for hormone support and other uses. It turns into active compounds like DIM in the stomach, so supplement dosing looks different from dietary intake.

So how much should you take? Most clinical trials use between 200 and 400 mg of I3C per day. Short-term studies sometimes go up to 600 mg daily, but higher and long-term dosing hasn’t been studied enough to call it safe. A sensible approach: start at 200 mg once daily for a week. If you tolerate it, switch to 100 mg twice daily or 200 mg twice daily, depending on your reason for taking it and your clinician’s advice.

Timing, form, and diet tips

Take I3C with food — that reduces stomach upset and helps absorption. Capsules and tablets are common; buy products that list the exact I3C content per serving. If you prefer food sources, eat raw or lightly cooked cruciferous vegetables (broccoli, cabbage, Brussels sprouts) since heavy cooking breaks down the compounds. Note: many people take DIM supplements instead because DIM is a direct metabolite and stays more stable. DIM doses are often lower (for example, 100–300 mg daily) because it’s already in a more active form.

Safety, interactions, and monitoring

Common side effects are mild: nausea, gas, headache, or a skin rash. Stop and see a doctor for severe symptoms like jaundice, intense abdominal pain, or allergic signs. Don’t use I3C if you’re pregnant or breastfeeding — safety data is lacking.

I3C affects estrogen metabolism. If you have a hormone-sensitive condition (breast, ovarian, endometrial, or prostate cancer) or you’re on hormone therapy, talk to your oncologist or endocrinologist first. I3C may also change activity of liver enzymes (CYPs) and alter blood levels of certain drugs — think blood thinners, some statins, and some antidepressants. If you’re on prescription meds, ask a pharmacist whether an interaction is possible and whether lab checks (like INR or liver enzymes) are needed.

How long should you take it? Many studies run for 6–12 weeks. For specific medical goals, your clinician may suggest periodic labs (liver tests, hormone panels) and follow-up. For general supplementation, reassess the need every few months instead of taking it indefinitely without supervision.

Practical checklist: start low and split doses, buy third-party tested brands, keep a symptom diary for the first month, and stop if you see worrying changes. If I3C causes GI trouble, consider switching to DIM after checking with your provider. Medical guidance beats internet rules of thumb — always run supplement plans by a clinician when you have chronic conditions or take regular medications.