If you take more than one medication — including over-the-counter drugs, vitamins, and supplements — you're at risk for drug interactions. According to WHO data, adverse drug interactions cause approximately 125,000 deaths per year in the US alone.

A drug interaction occurs when one substance affects the activity of another. This can happen between:

- Two or more prescription drugs

- Prescription and OTC medications

- Drugs and supplements (especially St. John's Wort, ginkgo, grapefruit)

- Drugs and food/beverages (alcohol, grapefruit juice, dairy)

Drug-Drug: One medication changes how another works. Example: taking ibuprofen with blood thinners increases bleeding risk.

Drug-Food: Certain foods affect drug absorption or metabolism. Example: grapefruit juice dramatically increases levels of some statins.

Drug-Supplement: Herbal supplements can interact dangerously. Example: St. John's Wort reduces effectiveness of birth control pills, antidepressants, and HIV medications.

- Blood thinners + NSAIDs (warfarin + ibuprofen): increased bleeding risk

- SSRIs + triptans (antidepressants + migraine drugs): serotonin syndrome risk

- ACE inhibitors + potassium supplements: hyperkalemia risk

- Metformin + alcohol: lactic acidosis risk

- Statins + grapefruit: increased statin levels and muscle damage risk

1. Keep a complete medication list — include all prescriptions, OTC drugs, vitamins, and supplements

2. Use an interaction checker — PillsCard's tool lets you check multiple drugs at once

3. Tell every doctor about every medication — including what other doctors prescribed

4. Use one pharmacy — your pharmacist can catch interactions across prescribers

5. Read labels — look for interaction warnings on OTC medications

If you experience unexpected symptoms after starting a new medication or combining drugs — especially dizziness, unusual bleeding, rapid heartbeat, or confusion — contact your doctor immediately.