Medicine blood level test

Certain types of medicine need to be monitored because:

• At a low blood level, they don't work as well as they should.
• At a high blood level, they may cause problems.

Your doctor may use your test results to adjust your dose.

You may need testing when you take medicines such as:

• Cyclosporine and tacrolimus, which help control the immune system.
• Digoxin, which helps the heart pump blood better.
• Gentamicin and vancomycin, which are antibiotics.
• Lithium, which affects brain chemicals.

A health professional uses a needle to take a blood sample, usually from the arm.

Depending on the kind of medicine you take, your doctor may schedule your test at a certain time of day. For example, you may have your test in the morning, before you take your medicine. Or your test might be after you take your medicine.

A medicine blood level test measures how much of your medicine is in your blood. Your doctor checks it to make sure that you're taking a safe and effective dose. This testing is also called therapeutic drug monitoring.

The medicine blood level is just a guide. Your doctor will also look at your results based on your age, health, and other factors to help decide whether you are taking the right amount of medicine.