Finding and Learning about Side Effects (adverse reactions)

Finding and Learning about Side Effects (adverse reactions)

From Minor to Life Threatening

Unwanted or Unexpected Drug Reactions

Drugs approved by the U.S. Food and Drug Administration (FDA) for sale in the United States must be safe --

which means that the benefits of the drug appear to be greater than the known risks --and effective. However, both prescription and over-the-counter (OTC) drugs have side effects. Side effects, also known as adverse events, are unwanted or unexpected events or reactions to a drug. Side effects can vary from minor problems like a runny nose to life-threatening events, such as an increased risk of a heart attack.

Several things can affect who does and does not have a side effect when taking a drug – age, gender, allergies, how the body absorbs the drug, other drugs, vitamins and dietary supplements that you may be taking. Common side effects include upset stomach, dry mouth, and drowsiness. A side effect is considered serious if the result is: death; life-threatening; hospitalization; disability or permanent damage; or exposure prior to conception or during pregnancy caused birth defect.

Side effects can happen when you:


  • start taking a new drug, dietary supplement, or vitamin/mineral
  • stop taking a drug that you’ve been on for a while, or
  • when you increase or decrease the amount of a drug that you take.

Reducing Your Risk

There are several ways to learn about side effects for your drugs and to reduce your risk of experiencing a side effect.

  • Ask your health care professional about any possible side effects and what, if any steps should be taken to reduce the risk when you are prescribed a drug. For example, he or she may recommend taking the drug with food to lower the chance of getting nausea.
  • Ask your pharmacist for the patient prescribing information when you receive your prescription. This document will include possible common and serious side effects.
  • Read the pharmacy label and any stickers that may be attached to the prescription bottle. The label and stickers have information on how to take the drug and possible side effects.

Read the Drug Facts Label for over-the-counter drugs. Prescription drug information on side effects is available through FDA’s web-based Index to Drug-Specific Information and Drugs@FDA database.

When a Side Effect Occurs

Should you experience a side effect, you may be able to lessen or eliminate the effects. Work with your health care professional to see if adjusting the dosage or switching to a different medication will ease or eliminate the side effect. Sometimes simply switching from two separate medications to a combination product, if available, will make a difference. Other options, such as a lifestyle or dietary change, may be suggested by your health care professional.

Reporting Side Effects

When side effects do occur, you are encouraged to report them to FDA’s MedWatch, a program for reporting serious problems with human medical products including drugs.

MedWatch has a consumer reporting form, FDA 3500B. Written in plain language and designed to be consumer friendly, the form starts off with a page of some commonly asked questions and answers to help guide the user in submitting the form, and then asks simple questions about the problem. In addition to formal reports, MedWatch has a toll free line (1-800-332-1088) to answer questions.

Be an active member of your health care team. By taking time to learn about the possible side effects of a drug and working with your health care provider and pharmacist, you will be better prepared to reduce your chance of experiencing a side effect or coping with any side effect that you may experience.

Where Can I Find Detailed Side Effect Information for a Drug?

DailyMed, from NIH, contains detailed information about FDA-approved drugs. Please use these instructions to find information about a particular drug.

Find Drug Side Effects (Adverse Reactions)- Go to Daily Med (NIH) - Enter Drug Name DailyMed - Click on drug name and scroll down to Adverse Reactions

 Resources with Side Effect Information