10 Supplements That Interact With the Most Prescription Drugs
These ten supplements carry the longest drug-interaction lists in our database, and the risks are real rather than theoretical — St. John’s Wort alone can blunt warfarin, antidepressants, birth-control pills and chemotherapy by speeding the liver’s drug-clearing machinery. The pattern repeats across the list: blood thinners stacked with omega-3, ginkgo or high-dose vitamin K2; serotonin drugs combined with 5-HTP or saffron; and common minerals like calcium, iron and zinc that bind antibiotics and thyroid medication if taken together. The single most useful habit is to tell your pharmacist about every supplement you take, because most of these interactions surface in real clinical case reports precisely when patients assume herbs and minerals don’t count as drugs. When timing is the only issue — as with minerals and levothyroxine — separating doses by two to four hours usually solves it.
St. John's Wort interacts with about every drug class in your medicine cabinet — and that's the easy one. If you take a prescription, scan this list first. These are the ten supplements with the longest interaction tables in our database.
- St. John's Wort — Warfarin, SSRIs, MAOIs, oral contraceptives, chemotherapy. The poster child for "natural ≠ inert."
- Berberine — Statins, metformin, BP meds, diabetes drugs, antifungals.
- Magnesium — Thyroid hormone, PPIs, antibiotics, benzos, sleep meds.
- Omega-3 (high dose) — Bleeding risk on top of warfarin, DOACs, and antiplatelets.
- Ginkgo biloba — Antiplatelet, anticoagulant, and seizure-threshold concerns.
- 5-HTP — SSRIs, MAOIs, triptans — serotonin syndrome risk.
- Saffron — Antidepressants, blood thinners, blood-pressure meds.
- Melatonin — Seizure meds, sedatives, benzos. Effects amplify, not just stack.
- Vitamin K2 — Warfarin antagonism. Even MK-7 doses can drop INR meaningfully.
- Calcium / Iron / Zinc — Chelate fluoroquinolones, tetracyclines, levothyroxine, bisphosphonates. Separate doses by 2–4 hours.