Therapeutic Drug Monitoring

Therapeutic drug monitoring (TDM) is testing that measures the amount of certain medicines in your blood. It checks whether the amount of medicine you take is safe and effective. All medicines don't require therapeutic monitoring.

Usually, your health care provider can determine the right dose of medicine for you without special testing. But some medicines must maintain a certain level in your blood to work well. This is called the 'therapeutic dose level.' As soon as you take medicine, your body begins to process and remove the medicine from your body.

This means that the level of the medicine in your blood will vary over time. Many things can affect how quickly this process happens, including: Aging.; Pregnancy.; Illness.; Infection.; If you're taking a medicine that needs to be kept at a certain level, it can be hard to figure out which dose provides enough medicine to treat your condition without causing dangerous side effects. TDM helps your provider figure out if you are taking the right dose of your medicine.

Why this test is done

You may need testing when you first start taking a medicine. This helps your provider figure out the most effective dose for you. Once that dose is determined, you may be tested regularly to make sure the medicine is still effective without being harmful.

You may also need testing if you have symptoms of a serious side effect. Side effects can vary, depending on the medicine. Your provider will tell you which symptoms to watch out for.

How to prepare

Depending on the type of medicine you are taking, you may need to schedule your test before or after taking your regular dose. Be sure to tell your provider if you are taking other medicines or supplements, in case they affect the results.

Sample type

Blood

Other names for this test

medicine levels blood test, therapeutic drug levels