Enter up to 20 medications to check for interactions.
For informational purposes only. Not a substitute for professional medical advice. Always consult your doctor or pharmacist.
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Type or scan your medications
Autocomplete resolves each drug to its exact FDA identity. Or tap the camera icon to scan a pill bottle label directly.
Add up to 20 drugs at once
CDI computes every possible pair combination simultaneously — unlike most checkers that handle only two drugs.
See severity-ranked results
Contraindicated interactions surface first. Every result links back to the actual FDA label — not a third-party summary.
Every approved U.S. drug label parsed for interaction warnings.
Unique drug-pair interactions with severity classifications.
Every possible pair combination — so nothing slips through.
Contraindicated, major, moderate, and minor — not just a yes/no answer.
A drug interaction occurs when one medication alters the way another works in your body — raising or lowering blood levels, amplifying side effects, or blocking the intended effect altogether. Interactions can occur between two prescription medications, between a prescription and an over-the-counter drug, or between a drug and a food, supplement, or herbal product.
The consequences range widely. A minor interaction might cause a slight reduction in a drug's effectiveness with no immediate danger. A moderate interaction may require dosage adjustments or closer monitoring. A major interaction can cause clinically significant harm and usually means one drug should be substituted. A contraindicated combination should never be used together under any circumstances.
The U.S. FDA estimates that drug interactions account for approximately 3–5% of all in-hospital medication errors — the vast majority of which are preventable with proper screening. That is why checking interactions before starting a new medication matters, particularly for patients managing multiple chronic conditions.
The following are some of the most clinically significant interactions documented in FDA drug labeling. They illustrate why routine interaction screening is part of standard pharmacy practice.
Combining warfarin with aspirin significantly increases bleeding risk. Aspirin inhibits platelet aggregation while warfarin reduces clotting-factor synthesis — the combination can cause serious gastrointestinal or intracranial bleeding.
NSAIDs like ibuprofen can blunt the antihypertensive effect of ACE inhibitors such as lisinopril by inhibiting prostaglandin synthesis and reducing renal blood flow. Blood pressure should be monitored when both are used.
Amiodarone inhibits CYP3A4, the enzyme responsible for metabolizing simvastatin. Co-administration can raise simvastatin blood levels dramatically, increasing the risk of myopathy and rhabdomyolysis.
Iodinated contrast agents used in imaging can temporarily impair kidney function. Since metformin is cleared by the kidneys, reduced clearance can lead to lactic acidosis — a rare but serious condition. Metformin is typically held 48 hours before and after contrast procedures.
Enter any drug name — brand or generic — into the search fields above. Our autocomplete draws from the NIH RxNorm database to identify the canonical drug name and its RxCUI identifier. Once you have confirmed at least two drugs, click Check Interactions to see every pair evaluated simultaneously.
Results are ranked by severity — contraindicated interactions surface first so the most urgent risks are never buried. Each result card shows the FDA-documented description, the pharmacological mechanism where available, and the specific FDA drug label the data was sourced from.
The checker supports up to 20 drugs at once — covering the full complexity of polypharmacy regimens common in elderly patients, oncology, and chronic disease management. On mobile, you can photograph a pill bottle label and our OCR feature will extract and search the drug name automatically.
A drug interaction occurs when one medication changes the way another medication works in your body. Interactions can increase a drug's side effects, reduce its effectiveness, or — in serious cases — cause life-threatening reactions. They can happen between two prescription drugs, between a prescription and an over-the-counter drug, or between a drug and a food or supplement.
Drug interactions range from minor (slight reduction in effectiveness, no action needed) to moderate (may require monitoring or dosage adjustment) to major (serious harm possible, generally avoid the combination) to contraindicated (should never be taken together). The FDA estimates drug interactions account for 3–5% of all in-hospital medication errors.
Every interaction on checkdruginteractions.com is sourced directly from U.S. FDA-approved drug labeling, processed through the openFDA API and the NIH National Library of Medicine's DailyMed database. We index over 257,000 FDA drug labels. We do not invent or infer interactions — if it appears here, it is explicitly documented in official FDA labeling.
Yes. Our checker supports up to 20 drugs simultaneously. When you enter multiple drugs, we calculate every possible pair (n choose 2) and display all interactions ranked by severity — contraindicated results first, then major, moderate, and minor. This makes it easy to review a full medication list at once.
Not necessarily. "No interaction found" means no interaction between those two drugs appears in our FDA label dataset. Interaction databases are updated as new information emerges, and individual patient factors — kidney function, genetics, other medications — can affect risk. Always confirm with your pharmacist or physician before combining medications.
No. checkdruginteractions.com is an informational reference tool. Your pharmacist has access to your full medication history and can apply clinical judgment to your specific situation. This tool helps you arrive at that conversation informed — not replace it.