therapeutic-drug-monitoring
Reviewed
Therapeutic drug monitoring (TDM) measures the amount of certain medicines in your blood to check whether the dose is safe and effective. It helps your provider determine the right dose for medicines that must stay within a specific range in your blood to work well and avoid dangerous side effects.
Preparation and collection
Depending on the type of medicine you are taking, you may need to schedule your test before or after taking your regular dose. Tell your provider about any other medicines or supplements you take, as they may affect the results.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- The therapeutic range varies depending on the type of medicine and your own health needs.
- Many factors such as aging, pregnancy, illness, infection, and other medicines can affect how quickly your body processes the medicine, leading to changes in blood levels.
- Results are interpreted by your healthcare provider, who will adjust your dosage as needed.
What to do next
If your results are not in the therapeutic range, your provider may need to adjust your dosages. If your dosages change, you may get repeated tests until your medicine levels fall into the therapeutic range. Talk to your provider if you have questions about your results.
Evidence source
U.S. National Library of Medicine: therapeutic-drug-monitoring