Learn about common and serious Clarithromycin side effects, who's at higher risk, and when to call your doctor. Includes tips for managing metallic taste, nausea, and more.
Clarithromycin (formerly sold as Biaxin) is a macrolide antibiotic prescribed for everything from sinus infections to H. pylori ulcers. Like all antibiotics, it comes with potential side effects — some annoying but harmless, and others that need immediate medical attention.
This guide covers what clinical trials and FDA labeling actually say about Clarithromycin's side effects, so you know what to expect and when to call your doctor.
Clarithromycin is a macrolide antibiotic that works by stopping bacteria from making the proteins they need to grow. It's used to treat bacterial infections of the lungs, sinuses, skin, and stomach. It comes as immediate-release tablets (250 mg, 500 mg), extended-release tablets (500 mg), and an oral suspension for children.
A typical course lasts 7 to 14 days, and most people tolerate it well. But side effects do happen — here's what to watch for.
These side effects are the most frequently reported in clinical trials. They're usually mild and go away on their own once you finish your course:
These are less common but require prompt medical attention. Contact your doctor immediately — or go to the emergency room — if you experience any of the following:
Clarithromycin can affect the electrical activity of your heart, leading to a condition called QT prolongation. This can cause dangerous irregular heartbeats (arrhythmias), including a potentially fatal rhythm called torsades de pointes.
Warning signs: Rapid or irregular heartbeat, dizziness, fainting, or feeling like your heart is "fluttering."
Important: In 2018, the FDA issued a safety communication warning about increased risk of heart problems or death in patients with heart disease who took Clarithromycin. If you have any heart condition, make sure your doctor knows before starting this medication.
Clarithromycin can cause liver injury, ranging from mild enzyme elevations to more serious conditions like cholestatic jaundice.
Warning signs: Yellowing of the skin or eyes (jaundice), dark urine, unusual fatigue, upper-right abdominal pain, loss of appetite.
All antibiotics can disrupt your normal gut bacteria and allow C. difficile to overgrow, causing severe, watery diarrhea that can become life-threatening.
Warning signs: Watery diarrhea that doesn't stop (more than 3 loose stools per day), fever, abdominal cramping or tenderness, blood or mucus in stool. This can occur during treatment or even weeks after finishing your course.
Anaphylaxis and severe skin reactions like Stevens-Johnson syndrome (SJS) are rare but documented with Clarithromycin.
Warning signs: Hives, swelling of the face/throat/tongue, difficulty breathing, widespread skin rash with blistering or peeling, fever with rash.
Kidney problems have been reported, particularly in patients taking other nephrotoxic medications.
Warning signs: Decreased urination, swelling in legs or feet, unusual fatigue, confusion.
Patients with myasthenia gravis may experience a flare-up of symptoms.
Warning signs: Increased muscle weakness, difficulty swallowing or breathing, drooping eyelids.
Reversible hearing loss or ringing in the ears (tinnitus) has been reported, usually at higher doses.
Warning signs: Muffled hearing, ringing or buzzing in the ears, difficulty understanding speech.
Patients over 65 may be more susceptible to QT prolongation and heart rhythm problems. Kidney function naturally declines with age, which can increase Clarithromycin levels in the blood and raise the risk of side effects.
In pediatric clinical trials, the most commonly reported side effects were diarrhea, vomiting, abdominal pain, and rash. The oral suspension may be better tolerated than tablets. Clarithromycin is not approved for infants under 6 months.
Clarithromycin is Pregnancy Category C — meaning animal studies showed adverse effects, and there aren't enough human studies to confirm safety. It should only be used during pregnancy if the potential benefit justifies the risk. Clarithromycin is excreted in breast milk, so breastfeeding mothers should discuss alternatives with their doctor.
If you have severe kidney impairment (CrCl below 30 mL/min), your doctor should reduce your dose or extend the dosing interval. Patients with liver disease should be monitored closely, as Clarithromycin is processed by the liver.
Most mild side effects can be managed with simple strategies:
Call your doctor promptly if you experience:
If you experience difficulty breathing, chest pain, or severe swelling, call 911 or go to the nearest emergency room.
Clarithromycin is an effective antibiotic for a wide range of infections, and most people complete their course without serious problems. The metallic taste is probably the most annoying side effect you'll encounter — and it goes away once you're done.
The key is knowing the difference between "uncomfortable but normal" and "call your doctor now." If you're not sure, err on the side of calling. That's what your doctor is there for.
Looking for more information? Read our full guide on what Clarithromycin is and how to take it, or check Clarithromycin drug interactions to make sure your other medications are compatible.
You focus on staying healthy. We'll handle the rest.
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