Drug Concentration: Hydrocodone and Acetaminophen (Paracetamol) in Serum/Plasma

Why This Test Is Done

Doctors may order this test if you’re taking hydrocodone (e.g., Vicodin, Norco) and acetaminophen (e.g., Tylenol) together for pain management. It’s especially important if you have kidney or liver issues, are taking other medications, or if you’ve had recent changes in your dose. This test can also be used to monitor overdose risks or drug interactions.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if it involves a blood draw. Wear comfortable clothing and plan to stay near the testing site for a short time. If you’re on blood thinners, let your doctor know beforehand.

What Happens During the Test

A healthcare provider will take a blood sample from a vein in your arm. You may feel a slight pinch, but it’s usually over quickly. The blood is then sent to a lab for analysis. Results are typically ready within 24–48 hours, depending on your healthcare provider’s process.

What the Results Mean

Results show the concentration of hydrocodone and acetaminophen in your blood. Low levels may mean your medication isn’t working well, while very high levels could indicate overdose or poor metabolism. Your doctor will interpret these results in the context of your symptoms, other medications, and medical history.