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Supplement & Drug Interaction Checker

Taking prescription medication? Search your drug to see which supplements are safe, require monitoring, or must be avoided — based on clinical pharmacology and CYP enzyme data.

Search your medication

Enter a prescription drug name (brand or generic). Common examples: warfarin, metformin, levothyroxine, SSRIs, statins, blood pressure medications.

Common searches: Warfarin Metformin Levothyroxine Sertraline (Zoloft) Atorvastatin (Lipitor) Lisinopril Amlodipine Aspirin

High-Risk Drug-Supplement Pairs Everyone Should Know

🚫 Warfarin + Vitamin K2

K2 directly antagonises warfarin's anticoagulant mechanism. Can cause dangerous clotting if K2 is added or removed while on warfarin. Requires INR monitoring and physician guidance.

🚫 SSRIs + St John's Wort

Serotonin syndrome risk. St John's Wort inhibits serotonin reuptake — combined with SSRIs can cause dangerous serotonin excess (agitation, tremor, hyperthermia, seizure).

🚫 Statins + Berberine

Berberine inhibits CYP3A4, which metabolises most statins. Can significantly raise statin blood levels, increasing myopathy and rhabdomyolysis risk.

🚫 Levothyroxine + Magnesium/Calcium/Iron

All three minerals chelate levothyroxine in the gut, dramatically reducing absorption. Space levothyroxine at least 4 hours from any mineral supplement.

⚠ Metformin + Berberine

Additive blood glucose-lowering. Can cause hypoglycaemia. Requires blood glucose monitoring and possible metformin dose reduction under physician guidance.

⚠ Blood thinners + Fish Oil >3g/day

High-dose omega-3 has antiplatelet effects that add to warfarin, aspirin, or clopidogrel. Disclose fish oil use to your prescriber — dose adjustment may be needed.

FAQs

Do I need to tell my doctor about supplements?
Yes — always. Many people don't mention supplements because they consider them "natural" and therefore safe. But supplements can significantly alter drug metabolism (via CYP enzymes), compete for absorption (minerals with medications), or have additive pharmacological effects (blood thinning, blood sugar lowering). Your prescriber needs a complete picture of everything you take. Keep a list that includes all supplements with doses.
What are CYP enzymes and why do they matter?
CYP (cytochrome P450) enzymes are the primary pathway by which the liver metabolises drugs and many supplements. If a supplement inhibits CYP3A4 (berberine, grapefruit, St John's Wort), drugs cleared by that enzyme build up to higher blood levels — potentially causing toxicity. If a supplement induces CYP enzymes (St John's Wort for CYP3A4), it accelerates drug clearance — reducing drug effectiveness. These interactions can be clinically significant at standard supplement doses.
Is the interaction the same regardless of dose?
No — most drug-supplement interactions are dose-dependent. For example, 1,000mg omega-3/day has minimal antiplatelet effect; 4,000mg/day has meaningful blood-thinning that matters clinically if you're on warfarin. This is why the tool flags dose thresholds where relevant. Always disclose your specific dose to your pharmacist.