Ideally, a serum drug level would be monitored frequently and consistently, providing the clinician with a detailed pharmacokinetic profile over time.
In reality, serum samples are often measured only during relatively infrequent clinic visits, which means that many days or weeks may pass before a drug concentration 'snap-shot' is taken.
The timing of when to collect for TDM testing is important to consider. Patients often rely on the lab to advise them on whether they should be collected for a drug level when they present to the lab phlebotomist.
