Clarithromycin: what it treats, how to take it, side effects
Last updated September 3, 2026.
Clarithromycin is a macrolide antibiotic - it stops bacteria from growing. A workhorse for respiratory and skin infections, and a notorious mixer: its interaction list is one of the longest in the antibiotic cabinet.
What does it treat?
Certain bacterial infections - ears, sinuses, throat, lungs, and skin among them. Like every antibiotic: nothing for colds, flu, or any virus.
How do you take it?
Exactly as directed, on the schedule written for you - immediate-release tablets with or without food, extended-release with food, the suspension shaken well. A metallic or changed taste is common and temporary. Finish the full course. The complete medication list matters more on this drug than most: it blocks a major drug-metabolizing enzyme, so statins, colchicine, blood thinners, and many others need the pharmacist screen. Missed dose: take it when you remember unless the next one is close; never double up.
Side effects to know
- Common: diarrhea, nausea, vomiting, stomach pain, heartburn, gas, change in taste, and headache.
- Serious - call your doctor immediately or get emergency care: chest pain, shortness of breath, trouble breathing, pain or weakness on one side of the body, or slurred speech - the heart and stroke set; severe watery or bloody diarrhea during or up to 2 months after; and the allergic set - rash, itching, hives, swelling of face, throat, tongue, lips, eyes, or lower legs, difficulty breathing or swallowing, hoarseness.
Who should not take it?
Flag heart-rhythm problems - macrolides can disturb the rhythm - plus liver and kidney disease, and myasthenia gravis, which macrolides can worsen. Anyone on a statin, colchicine, or a blood thinner: the combination decision belongs to the prescriber, not the medicine cabinet. If you become pregnant, call your doctor.
When is it an emergency?
Chest pain with trouble breathing, slurred speech, one-sided weakness, or throat swelling is a 911 call. For an overdose, call Poison Control at 1-800-222-1222. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
What a Pymander AI doctor consult looks like
Illustrative example, not a real member's messages.
Common questions
Why did the pharmacist hold my statin?
Clarithromycin blocks the enzyme that clears many statins - levels climb, and with them the risk of muscle damage. The standard move is pausing the statin for the antibiotic week: safe, simple, and arranged through the pharmacist or prescriber. Colchicine, some blood thinners, and a long list of others get the same screen. On this antibiotic, "the pharmacist checked my list" is the safety system working, not a hassle.
Why does everything taste like metal?
A known, harmless effect - clarithromycin reaches saliva and distorts taste, usually metallic. It lasts the course and clears after. Cold drinks, mints, and brushing before meals take the edge off. Annoying, but a fair trade for an infection on the run - and it resolves completely when the drug does.
Why the heart questions before prescribing?
Macrolides can prolong the heart's electrical cycle - in people with rhythm problems or certain interacting medications, that tips toward dangerous rhythms. The chest pain, shortness of breath, one-sided weakness, and slurred speech items on the serious list are the reason the screening happens first. Most people take it without incident; the questions are what keep it that way.
Why finish the course if the pressure is gone?
Symptom relief means bacterial numbers are down, not out - the survivors of a half-finished course are the resistant ones, and they regrow the infection harder to treat. Antibiotics also carry a delayed tail: severe watery or bloody diarrhea can appear during treatment or up to 2 months after - that pattern is always a call, not a wait.
How is this different from amoxicillin?
Different families, different coverage: clarithromycin is a macrolide - the standard alternative when penicillin allergy rules out amoxicillin, and the better fit for some bacteria and for combination regimens. The trade-off is the interaction load: amoxicillin mixes with almost everything; clarithromycin mixes carefully. Which one is yours depends on the bug, your allergy history, and your medication list.
What happens if I miss a dose of clarithromycin?
Take it as soon as you remember, unless it is almost time for the next one - then skip it and never double up. Twice-daily antibiotics work on steady levels: the breakfast-and-dinner anchor keeps the gaps from becoming the pattern that breeds resistance.