What does a serum drug test measure?

A serum drug test specifically measures the concentration of a drug in the blood serum. This is crucial for determining whether the drug levels are within a therapeutic range, which helps assess how well a patient is responding to a treatment. Monitoring serum drug levels can also help prevent toxicity, ensuring the drug is not at a level that could cause harm.

While the effectiveness of a drug in treating an illness is important, it cannot be directly measured through a serum drug test; rather, that effectiveness is often evaluated through clinical assessments and patient outcomes. Tissue distribution of a drug and the interval of drug administration are also relevant pharmacokinetic factors, but they do not pertain to the specific measure of drug concentration in blood serum that this test is designed to evaluate.