Serum or plasma morphine concentration (mass concentration)

Why This Test Is Done

Your healthcare provider may order this test if you’re taking morphine for pain relief, if you’ve experienced symptoms like confusion, slow breathing, or unusual sleepiness, or if you’re being evaluated for drug use or toxicity.

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. If you’re concerned about needles, let your doctor know—they may use a different method, like a fingerstick for a quick sample.

What the Test Results Mean

Results show how much morphine is in your blood at the time of testing. High levels may indicate recent use, overdose, or improper metabolism. Very low levels might suggest the drug isn’t working as expected or you’re not taking it as prescribed.

Possible Side Effects or Risks

The most common side effect is a small bruise or slight discomfort at the injection site. Rarely, blood tests can cause allergic reactions or infections, though these are uncommon with modern medical practices.