What is blood level testing?

Blood level testing, an important part of therapeutic drug monitoring (TDM), measures the amount of medication in the patient's blood.

Why do doctors monitor the blood levels of oral medications used to treat cancer?

Blood level testing lets the doctor check the amount of medication in a patient's blood. This information is important, because blood levels can cary from person to person, even with the same dose of medication. Also, blood levels may inform a doctor if a patient has been taking a medication incorrectly, or skipping doses.

When should medication blood levels be measured?

Some doctors have blood levels tested soon after the start of treatment, or after a change in dosing, to set a "baseline" level. Your doctor may also wish to measure the levels of medication in your blood at other times in the course of treatment, to compare the levels of medicine in your blood to the "baseline" level.