Drug Side Effects
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Search any drug to see its adverse reactions, warnings, and cautions directly from the official FDA drug labeling. Data is sourced from OpenFDA — the same information on the package insert.
How to read a drug side effects list
The information displayed on this page is taken directly from the official FDA drug label (also called the prescribing information or package insert). These labels are written by the drug manufacturer and approved by the FDA. Understanding what you're reading helps you use this information appropriately.
This section lists side effects that were observed during clinical trials. It typically includes both common and rare effects. "Adverse reaction" in FDA labeling means a harmful and unintended response to a drug at any dose.
Warnings describe serious adverse reactions that may be life-threatening. Boxed warnings (the "black box") are the FDA's strongest warning and indicate serious risks. These should be carefully reviewed before starting a medication.
This section covers serious adverse reactions that are not in the boxed warning but require careful monitoring. It also includes special populations such as patients with kidney or liver disease, or who are pregnant.
Side effects listed do not mean you will experience them. Common side effects (occurring in more than 1 in 10 people) are different from rare but serious ones. Your risk depends on your dose, health status, and other medications.
Common vs. serious side effects
Not all side effects are equally concerning. Most medications cause minor side effects that resolve on their own. Understanding the difference helps you decide when to seek medical attention:
- Very common (>1 in 10): Typically listed prominently; often mild (e.g., nausea, headache, drowsiness)
- Common (1–10 in 100): Reported by a meaningful proportion of users; should be mentioned to your doctor if troublesome
- Uncommon (1–10 in 1,000): Less frequent but still documented; worth knowing about
- Rare (<1 in 1,000): Unlikely to occur but can be serious; listed so patients can recognize them
- Very rare (<1 in 10,000): Documented in post-marketing reports; often serious reactions that emerged after approval
What to do if you experience a side effect
⚠ If you experience a serious side effect — difficulty breathing, severe allergic reaction, chest pain, severe rash, or any symptom that feels dangerous — call 911 immediately or go to your nearest emergency room. For non-emergency side effects, contact your doctor or pharmacist. Do not stop a prescribed medication abruptly without medical guidance.
- Keep a note of when the side effect started, how severe it is, and anything that makes it better or worse
- Contact your doctor if a side effect is bothersome or persisting beyond a few days
- Do not stop a medication suddenly unless instructed — abrupt discontinuation can sometimes be more dangerous than the side effect
- Report side effects to the FDA via MedWatch (fda.gov/safety/medwatch) — this helps improve drug safety for everyone
- Verify that what you are experiencing is not actually a symptom of the condition being treated, which can be hard to distinguish
- Check for drug interactions if you recently started an additional medication — new symptoms may be an interaction, not a side effect
Why side effects vary between people
The same drug can cause very different reactions in different people. Your individual response to a medication depends on many factors:
- Genetics: Pharmacogenomics — how your genes affect drug metabolism — accounts for many individual differences in both efficacy and side effects
- Age: Older adults often process drugs more slowly, increasing the risk of side effects and drug accumulation
- Kidney and liver function: These organs clear most drugs; impaired function raises drug levels and the chance of adverse effects
- Body weight: Affects drug distribution throughout the body; fixed doses may be too high or too low depending on size
- Other medications: Drug interactions can amplify or mask side effects
- Diet and lifestyle: Foods, alcohol, and smoking can alter how drugs are absorbed and broken down
About our data
Side effect information on this page is sourced from OpenFDA, the U.S. Food and Drug Administration's open data platform. The content reflects the official drug labeling approved by the FDA and is the same information found in the package insert. Labels are updated when new safety information becomes available. Always consult a licensed healthcare professional for personalized medical advice.