Potential side effects: what to watch for and how to act

Medications help a lot, but they can also cause unwanted reactions. Some side effects are mild and predictable—like an upset stomach after antibiotics—while others can be serious. This page gives clear, practical steps to spot problems fast, reduce risk, and get the right help when you need it.

How to recognize side effects

Timing matters. A side effect might show up right after the first dose, after a few days, or only after weeks. Watch for new or worsening symptoms that start after you begin a drug. Common warning signs include severe rash or itching, swelling of face or throat, trouble breathing, chest pain, fainting, sudden confusion, high fever, yellowing skin or eyes, dark urine, or unexplained bruising and bleeding.

Some drugs have typical patterns. For example: steroids (like prednisone) can change mood and appetite; proton pump inhibitors (like pantoprazole) sometimes cause headaches or diarrhea; antifungals (like terbinafine/Lamisil) rarely affect the liver; certain antibiotics (like azithromycin) can upset the stomach or, rarely, affect heart rhythm. Dapsone can cause anemia in people with G6PD deficiency. These are examples—each person reacts differently.

What to do if you suspect a side effect

If symptoms are life‑threatening—difficulty breathing, swelling of throat, fainting, chest pain—call emergency services immediately. For less urgent but worrying effects, stop the new medication and contact your prescriber or pharmacist. Don’t abruptly stop some drugs (notably steroids); ask a clinician first because stopping suddenly can be risky.

Write down when symptoms started, what you took, and any other meds or supplements you’re using. This makes it faster for your provider to spot interactions or allergic reactions. Keep a single list of all prescriptions, OTC drugs, and herbal products and share it at every visit.

Check reliable sources for side effect info: the drug leaflet, Health Canada, or FDA databases. If you bought meds online, verify the pharmacy’s legitimacy and compare the pill appearance with trusted images. Counterfeit drugs can cause unexpected effects.

Talk to a pharmacist about interactions—many side effects come from drugs that don’t play well together. Use apps or interaction checkers for a quick look, but always confirm with a pharmacist or doctor before changing anything.

Report serious reactions to your local drug safety authority (for example, Health Canada or FDA MedWatch). Reporting helps track risks and can protect others. If a medication is in short supply or you get a different brand, ask your provider about alternatives and monitor for new reactions.

Side effects can be scary, but acting quickly and knowing the right steps lowers risk. Keep records, ask questions, and when in doubt, get professional advice—fast.