Serum/plasma concentration of angiotensin II receptor blocker (losartan) measured by immunoassay

Why This Test Is Done

Your healthcare provider may order this test if you’re taking losartan (a medication for blood pressure) and want to monitor your response to the treatment. It can also help assess whether your dose needs to be changed, especially if you’re experiencing side effects or not seeing improvements in your blood pressure.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if it’s a blood draw, but this depends on the lab’s instructions. Bring a list of all medications you’re taking, including over-the-counter drugs and supplements, to share with your provider.

What the Test Involves

A healthcare professional will draw blood from a vein in your arm. The sample is then sent to a lab for testing using an immunoassay method to detect losartan in your serum or plasma.

What the Results Mean

Results are typically reported as a concentration in nanograms per milliliter (ng/mL). While reference ranges vary by lab, lower-than-expected levels may suggest your medication isn’t working as intended, while very high levels could indicate potential issues like improper dosing or kidney problems.