Clarithromycin (Serum/Plasma) Concentration Measurement

Why This Test Is Done

Doctors may order this test if you’re taking clarithromycin (a medication like Biaxin) to treat or prevent bacterial infections, such as pneumonia, ear infections, or certain types of skin or urinary infections. It’s also used in cases where the infection is resistant to other antibiotics. Your doctor might also check levels if you’re taking clarithromycin long-term or have a condition that affects how your body processes drugs.

What to Expect Before the Test

No special preparation is needed for this test. You’ll have a small needle inserted into your arm or vein to draw a blood sample. It usually takes a few minutes. If you’re on a blood thinner, let your doctor know before the test.

What the Test Results Mean

The test result shows your current level of clarithromycin in your blood. This helps your doctor determine if your dose is too high, too low, or just right. For example, low levels might mean the antibiotic isn’t working well, while high levels could increase your risk of side effects like stomach upset or rash.

Possible Side Effects

Clarithromycin is generally well-tolerated, but some people may experience mild side effects like nausea, diarrhea, or stomach pain. Rarely, it can cause more serious reactions, such as liver problems or allergic reactions. If you notice unusual tiredness, yellowing of the skin/eyes, or severe rash, contact your doctor immediately.