What You Should Know About Clarithromycin Side Effects

If your doctor has prescribed Clarithromycin (brand name Biaxin), you're probably wondering what to expect in terms of side effects. Like all antibiotics, Clarithromycin can cause unwanted reactions — most of them mild and temporary, but a few that need immediate medical attention.

This guide covers the common and serious side effects of Clarithromycin, who's at higher risk, and exactly when you should call your doctor.

What Is Clarithromycin? (Quick Overview)

Clarithromycin is a macrolide antibiotic used to treat bacterial infections including pneumonia, bronchitis, sinusitis, strep throat, skin infections, and H. pylori (stomach ulcer bacteria). It works by stopping bacteria from making the proteins they need to grow. It comes in immediate-release tablets (250 mg and 500 mg), extended-release tablets (500 mg), and an oral suspension for children.

Common Side Effects

These are the side effects that occur most frequently with Clarithromycin. They're usually mild and go away on their own once you finish your course of treatment:

• Metallic or abnormal taste (dysgeusia) — This is one of the most distinctive Clarithromycin side effects. Many patients describe a persistent bitter or metallic taste that lasts throughout treatment. It's harmless but annoying.
• Diarrhea — Antibiotics can disrupt your gut bacteria, leading to loose stools. Mild diarrhea is common.
• Nausea — Stomach upset is fairly common, especially when taking Clarithromycin on an empty stomach.
• Vomiting — Less common than nausea but can occur, particularly in children.
• Abdominal pain or stomach discomfort — Cramping or a general "upset stomach" feeling.
• Headache — Usually mild and manageable with over-the-counter pain relievers.
• Dyspepsia (indigestion) — A burning or uncomfortable feeling in the upper stomach area.

Most of these common side effects affect roughly 3-10% of patients taking Clarithromycin.

Serious Side Effects — When to Call Your Doctor

While rare, some Clarithromycin side effects are serious and need immediate medical attention. Call your doctor or go to the emergency room if you experience any of the following:

Heart Rhythm Problems (QT Prolongation)

Clarithromycin can affect your heart's electrical system, causing a condition called QT prolongation. This can lead to dangerous irregular heartbeats (torsades de pointes). Seek emergency care if you notice:

• Fast, pounding, or irregular heartbeat
• Dizziness or feeling like you might faint
• Sudden loss of consciousness

Important FDA warning: In 2018, the FDA issued a safety communication about a potential increased risk of heart problems or death in patients with coronary artery disease who take Clarithromycin — even years after treatment. If you have heart disease, discuss this with your doctor.

Liver Problems (Hepatotoxicity)

Clarithromycin can, in rare cases, cause liver damage. Watch for:

• Yellowing of the skin or eyes (jaundice)
• Dark urine
• Severe fatigue
• Upper right abdominal pain
• Loss of appetite that doesn't improve

Severe Diarrhea (C. difficile Infection)

If diarrhea becomes severe, watery, or bloody — especially with stomach cramps and fever — it could be a sign of Clostridioides difficile (C. diff) infection. This can happen during or even weeks after finishing the antibiotic. Do not take anti-diarrheal medications without talking to your doctor first, as they can make C. diff worse.

Severe Allergic Reactions

Though uncommon, serious allergic reactions can occur. Call 911 or go to the ER immediately if you experience:

• Difficulty breathing or swelling of your face, lips, tongue, or throat (anaphylaxis)
• Severe skin rash, blistering, or peeling (could indicate Stevens-Johnson syndrome or toxic epidermal necrolysis)
• Hives with fever

Kidney Problems

Rarely, Clarithromycin can cause acute kidney injury, especially when combined with certain other medications like calcium channel blockers. Symptoms include decreased urination, swelling in your legs or feet, or unusual fatigue.

Hearing Changes

Some patients experience hearing loss or ringing in the ears (tinnitus) while taking Clarithromycin. This is usually reversible once the medication is stopped, but report it to your doctor right away.

Muscle Weakness

Clarithromycin can worsen myasthenia gravis, a condition that causes muscle weakness. If you have this condition and notice increased weakness, contact your doctor immediately.

Who's at Higher Risk for Side Effects?

Certain groups should be especially careful with Clarithromycin:

• People with heart disease — Higher risk of cardiac events, per the FDA's 2018 warning
• Patients with kidney impairment — Reduced clearance of the drug means higher blood levels and more side effects. Dose adjustment is needed when creatinine clearance is below 30 mL/min.
• Patients with liver problems — The liver metabolizes Clarithromycin; impaired liver function increases risk of toxicity
• Elderly patients — More susceptible to QT prolongation and drug interactions
• Pregnant women — Clarithromycin is Pregnancy Category C; animal studies showed adverse effects. Use only if the benefit clearly outweighs the risk.
• People taking multiple medications — Clarithromycin has many significant drug interactions that can increase side effects

How to Manage Common Side Effects

If you're experiencing mild side effects, these tips can help:

• For metallic taste: Try sugar-free mints, gum, or citrus-flavored drinks. The taste will go away after you finish treatment.
• For nausea or stomach upset: Take Clarithromycin with a small meal or snack. The extended-release version (Biaxin XL) must be taken with food.
• For diarrhea: Stay hydrated. Probiotics may help restore healthy gut bacteria. Avoid dairy if it makes symptoms worse.
• For headache: Over-the-counter pain relievers like Acetaminophen (Tylenol) are generally safe to take with Clarithromycin. Avoid Ibuprofen if you're having stomach issues.

Do not stop taking Clarithromycin early because of mild side effects unless your doctor tells you to. Stopping an antibiotic too soon can lead to antibiotic resistance and a return of the infection.

Final Thoughts

Most people who take Clarithromycin experience mild side effects — if any at all. The metallic taste and stomach upset are the most common complaints, and they go away once treatment ends. Serious side effects are rare but important to recognize.

The bottom line: take your full course as prescribed, know what to watch for, and don't hesitate to call your doctor if something doesn't feel right. If you're looking for the best price on your prescription, check our guide on saving money on Clarithromycin or use Medfinder to find it at a pharmacy near you.