Drug Interaction
Checker
Search and add two or more medications to check for known interactions. We query the NLM RxNav interaction database, FDA drug labels, and AI analysis simultaneously — no account required.
What are drug interactions?
A drug interaction occurs when one medication affects how another medication works in your body. Interactions can make a drug less effective, increase its effect to dangerous levels, or create unexpected new side effects. They can occur between two prescription drugs, between a prescription drug and an over-the-counter medication, between a drug and a dietary supplement, or even between a drug and certain foods or beverages.
These combinations are potentially life-threatening or capable of causing permanent damage. The combination should generally be avoided. Examples include mixing MAO inhibitors with certain antidepressants, or taking blood thinners with high-dose NSAIDs.
The combination may cause increased side effects or reduced effectiveness of one or both drugs. A dose adjustment or more frequent monitoring is often required. Your prescriber can usually manage these with careful oversight.
These are generally mild and often do not require a change in your therapy. However, they are worth knowing about. The clinical impact is small but may be noticeable, especially over time or at high doses.
We cross-reference three independent sources: NLM RxNav (the authoritative interaction database from the National Library of Medicine), OpenFDA drug label text, and AI analysis to catch drug-class level interactions that structured databases may miss.
When to call your doctor immediately
⚠ Contact your doctor or pharmacist right away if you experience any new or unusual symptoms after starting a medication or changing a dose. Always disclose every drug, supplement, and vitamin you take to every provider. In a medical emergency call 911, or reach Poison Control at 1-800-222-1222.
- A new medication has been prescribed while you are already taking other drugs
- You notice unexpected side effects after starting or changing a medication
- You feel unusually dizzy, confused, or have difficulty breathing
- Your blood pressure or heart rate changes unexpectedly
- You experience unusual or unexplained bruising or bleeding
- Your blood sugar becomes harder to control than usual
- You regularly take five or more medications (polypharmacy substantially increases interaction risk)
Common high-risk drug combinations
The following types of combinations are known to carry elevated risk and should always be discussed with a healthcare provider before taking them together:
- Warfarin + NSAIDs (ibuprofen, naproxen, aspirin) — significantly increased bleeding risk
- SSRIs + MAO inhibitors — risk of potentially fatal serotonin syndrome
- Statins + certain antibiotics or antifungals — risk of muscle breakdown (rhabdomyolysis)
- ACE inhibitors + potassium-sparing diuretics — risk of dangerous hyperkalemia
- Opioids + benzodiazepines — increased risk of respiratory depression and fatal overdose
- Metformin + iodinated contrast dye — risk of lactic acidosis; hold before imaging procedures
- Digoxin + amiodarone or verapamil — markedly elevated risk of digoxin toxicity
- Lithium + NSAIDs or thiazide diuretics — risk of lithium toxicity due to reduced renal clearance
Tips for managing multiple medications safely
If you take multiple medications — especially as you age — these strategies can substantially reduce your risk:
- Keep an up-to-date written list of all your medications, doses, frequencies, and reasons you take them
- Use the same pharmacy for all prescriptions — pharmacists can catch interactions across different prescribers
- Ask your doctor or pharmacist to review your complete medication list at every visit
- Read the patient information leaflet (PIL) that comes with every new medication
- Never stop a prescribed medication abruptly without consulting your prescriber first
- Always check for interactions before adding any over-the-counter drug or supplement
- Be aware that alcohol, grapefruit juice, and St. John's Wort have well-documented interactions with many common drugs