Medication Side Effects
Unwanted effects caused by medicines
Quick Facts
- Type: Adverse effects of medication
- Range: Mild and temporary to serious
- Higher risk: Multiple medications, older adults
- Emergency sign: Trouble breathing, swelling, severe rash
Overview
A medication side effect is any unwanted effect that occurs alongside a medicine's intended action. Almost all medications, including prescription drugs, over-the-counter products, supplements, and herbal remedies, can cause side effects in some people. Most are mild and go away as the body adjusts or after the medicine is stopped, but some can be serious.
Side effects are a very common and often overlooked reason for new or unexplained symptoms. Recognizing when a symptom might be caused by a medication, rather than by a new illness, can prevent unnecessary tests and additional prescriptions. This page gives a general overview; it is not a substitute for the specific information that comes with each medicine or for advice from a doctor or pharmacist about your own medications.
Symptoms
Side effects vary widely by medication, but some patterns are common. Frequently reported effects include:
- Nausea, stomach upset, diarrhea, or constipation
- Drowsiness, dizziness, or feeling lightheaded
- Headache
- Dry mouth
- Skin rash or itching
- Changes in appetite or weight
- A persistent dry cough (with certain blood pressure medicines)
More serious reactions can include severe allergic responses, abnormal bleeding, marked changes in heart rhythm, confusion, or signs of organ injury. A severe allergic reaction, with swelling of the face or throat, difficulty breathing, or a widespread rash, is a medical emergency.
Causes
Side effects arise for several reasons related to how medicines act in the body:
- The drug's action: A medicine often affects more than its intended target, producing predictable effects elsewhere.
- Dose: Higher doses or buildup of a drug, especially with reduced kidney or liver function, increases risk.
- Drug interactions: Combining medicines can amplify effects or create new ones.
- Individual differences: Age, body weight, genetics, and other health conditions affect how people respond.
- Allergy: The immune system may react to a medicine, sometimes severely.
Risk Factors
- Taking several medications at once (polypharmacy)
- Older age, with changes in how the body processes drugs
- Kidney or liver disease
- A history of drug allergies or previous reactions
- Starting a new medication or changing a dose
- Using supplements or herbal products alongside prescription drugs
Diagnosis
Identifying a medication side effect involves linking a symptom to a drug:
- Medication review: Listing all prescription drugs, over-the-counter products, and supplements, and when each was started.
- Timing: Noting whether symptoms began after starting or changing a medicine.
- Checking for interactions: A doctor or pharmacist can review combinations that may cause problems.
- Tests when needed: Blood tests to check drug levels or organ function, depending on the medicine.
Bringing an up-to-date list of all your medicines to appointments makes this much easier.
Treatment
How a side effect is managed depends on its type and severity, and should be guided by a clinician:
- Adjusting the medication: Lowering the dose, changing the timing, or switching to an alternative.
- Managing the symptom: Taking a medicine with food to reduce nausea, or treating a mild rash, when appropriate.
- Stopping the drug: Some side effects require stopping the medicine, but many drugs should not be stopped abruptly without medical advice.
- Treating serious reactions: Severe allergic or other dangerous reactions need urgent medical care.
Do not stop a prescribed medication on your own without checking with your doctor or pharmacist, as stopping some drugs suddenly can be harmful.
Prevention
- Keep an up-to-date list of all your medicines and supplements
- Tell your doctor and pharmacist about allergies and past reactions
- Use one pharmacy when possible so interactions can be checked
- Read the information that comes with each medicine
- Take medicines exactly as prescribed and ask questions if anything is unclear
- Review your medications periodically with your doctor, especially if you take several
When to See a Doctor
Contact your doctor or pharmacist if you think a medicine is causing bothersome or unexpected symptoms, rather than stopping it on your own. Call emergency services immediately for signs of a severe reaction, such as:
- Swelling of the face, lips, tongue, or throat, or difficulty breathing
- A widespread, blistering, or peeling rash
- Fainting, chest pain, or a very fast or irregular heartbeat
- Sudden severe weakness, confusion, or uncontrolled bleeding
These can be life-threatening and require urgent care. For overdose or poisoning, contact emergency services or a poison control center right away.
Frequently Asked Questions
What are medication side effects?
They are unwanted effects that a medicine can cause in addition to its intended benefit. Almost any drug, supplement, or herbal product can cause them. Most are mild and temporary, easing as the body adjusts or after stopping the medicine, but some can be serious and need medical attention.
How do I know if a symptom is a medication side effect?
Consider whether the symptom started after beginning or changing a medicine. Reviewing the timing with all your medications, including over-the-counter products and supplements, helps. A doctor or pharmacist can check for known side effects and drug interactions and advise whether the medicine is the likely cause.
Should I stop my medication if I have side effects?
Not on your own. Many drugs should not be stopped abruptly, and doing so can be harmful. Contact your doctor or pharmacist first; they may lower the dose, change the timing, switch you to an alternative, or reassure you that a mild effect will pass.
When is a medication reaction an emergency?
Call emergency services for swelling of the face or throat, difficulty breathing, a widespread blistering or peeling rash, fainting, chest pain, a very fast or irregular heartbeat, severe confusion, or uncontrolled bleeding. For a suspected overdose, contact emergency services or poison control immediately.
How can I reduce my risk of side effects?
Keep an up-to-date list of all your medicines and supplements, tell providers about allergies and past reactions, use one pharmacy so interactions can be checked, and take medicines exactly as prescribed. Periodic medication reviews are especially helpful if you take several drugs.
References
- U.S. Food and Drug Administration (FDA). Finding and learning about side effects.
- MedlinePlus, U.S. National Library of Medicine. Drug reactions.
- Mayo Clinic. Drug allergy — Symptoms and causes.
- Institute for Safe Medication Practices (ISMP).