Azithromycin: Uses, Dosing, Side Effects

Azithromycin is a commonly prescribed antibiotic used for many bacterial infections, from sinus and ear infections to certain STIs and some chest infections. It doesn’t work on viruses, so it won’t help with the common cold or most cases of bronchitis caused by viruses. Doctors like azithromycin because it’s easy to take and often works when other antibiotics don’t.

How to take azithromycin

Typical adult dosing depends on the infection. A common regimen for respiratory infections is 500 mg on day 1 then 250 mg once daily for the next 4 days. For some infections, a shorter course of 500 mg once daily for 3 days is used. A single 1 g dose is a standard option for chlamydia. Follow your prescriber's exact instructions—don’t change the dose on your own.

Take azithromycin with or without food. If you feel stomach upset, take it with a light meal. Avoid taking it at the same time as antacids that contain aluminum or magnesium; these can cut absorption. Space antacids at least 2 hours apart from azithromycin.

Finish the full course even if you feel better, unless your doctor tells you to stop. Stopping early can let bacteria survive and become resistant.

Safety, side effects and buying tips

Common side effects are mild: nausea, diarrhea, stomach pain, and headache. These usually pass quickly. Watch for serious signs like rash, swelling, fainting, trouble breathing, or fast/irregular heartbeat—these need immediate medical attention. Rarely, azithromycin can affect the liver or prolong the heart’s QT interval. If you already take medications that affect heart rhythm, tell your doctor before starting azithromycin.

Azithromycin can interact with other drugs. It may increase bleeding risk if you take warfarin. Combining it with other QT-prolonging drugs (certain antidepressants, antipsychotics, and some antiarrhythmics) raises the chance of heart rhythm problems. Always list your current medicines when a prescriber asks.

Pregnancy and breastfeeding: many doctors consider azithromycin a reasonable option during pregnancy and while breastfeeding, but always check with your clinician first. They’ll weigh benefits and risks for your situation.

Resistance is real. Overuse and improper use of azithromycin help bacteria become resistant, making future infections harder to treat. Use antibiotics only when prescribed for a confirmed or likely bacterial infection.

If you plan to buy azithromycin online, use a licensed pharmacy and expect to provide a valid prescription. Avoid sites that offer antibiotics without a prescription or that sell at unrealistically low prices. Check reviews, verify contact details, and look for secure payment methods. If something feels off, walk away and consult your doctor or a trusted pharmacy.

If you miss a dose, take it as soon as you remember unless the next dose is near—then skip the missed dose. Don’t double up. Store azithromycin at room temperature away from moisture and heat. If symptoms worsen or don’t improve in a few days, contact your provider for a re-check or a different treatment.