Trimethoprim Concentration in Serum/Plasma

Why This Test Is Done

Your healthcare provider may order this test if you’re taking trimethoprim (or a combination with sulfamethoxazole) to check whether the medication is at an appropriate level in your blood. This is especially important for managing infections like urinary tract infections, respiratory infections, or certain parasitic diseases.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for a few hours before the blood draw if your test involves fasting-related measurements. Bring a list of all medications, including over-the-counter drugs and supplements, to share with your provider.

During the Test

A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but it usually doesn’t cause discomfort. The process takes a few minutes, and you can resume normal activities afterward.

Possible Results and Interpretation

Results are compared to standard ranges for trimethoprim in blood, though exact values can vary based on your medical condition, dosage, and other factors. Your provider will discuss the results with you and explain what they mean in the context of your treatment.