Therapeutic Drug Monitoring Test
Therapeutic drug monitoring (TDM) measures the amount of certain medicines in your blood to check if the dose is safe and effective.
What this test measures
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.
What your results mean
Reference ranges vary by laboratory and by your age and sex. MedlinePlus does not publish a single normal range for this test — always read your result against the range printed on your own lab report and discuss it with your provider.
Higher-than-normal results
High levels of the medicine in your blood could make the drug unsafe.
Lower-than-normal results
Low levels of the medicine in your blood could make the drug less effective.
Frequently asked questions
What is therapeutic drug monitoring?
It is a blood test that measures the amount of certain medicines in your blood to see if the dose is safe and effective.
Which medicines need therapeutic drug monitoring?
Common ones include antibiotics (like vancomycin), heart medicines (like digoxin), anti-seizure medicines, and biologic medicines.
Why might I need TDM?
You may need TDM if you take a medicine that must stay at a certain level in your blood to work well and avoid side effects.
What can affect medicine levels in my blood?
Aging, pregnancy, illness, infection, and other medicines you take can affect medicine levels.
What do TDM results mean?
Results show if your medicine level is in the therapeutic range. If not, your provider may adjust your dose.
Related lab tests
Sources
- MedlinePlus: Therapeutic Drug Monitoring — NIH MedlinePlus
Last updated . Information is aggregated from official public sources and is not a substitute for professional medical care.