Serum Codeine Concentration (Free)

Why This Test Is Done

Your healthcare provider may order this test if you’re taking codeine for pain or cough relief, or if they suspect issues like drug interactions, liver problems, or how well your body is breaking down the medication. It can also help monitor overdose risks or guide dosage adjustments.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm or vein to draw blood. The process takes about 5 minutes, and you may feel a brief pinch. If you’re on blood thinners, let your provider know before the test.

What the Results Mean

Results show the concentration of free codeine in your blood. High levels may indicate overdose, poor metabolism, or improper dosing. Very low levels might suggest the medication isn’t working as expected or you’re metabolizing it too quickly. Always discuss results with your provider.

Common Causes of Abnormal Results

Abnormally high free codeine levels could be due to recent codeine use, liver disease (which slows metabolism), or drug interactions (e.g., with other painkillers or antidepressants). Low levels may result from rapid metabolism, skipping doses, or using codeine alternatives.