Toxicology tests can indicate the presence and concentration of medications or other substances, but interpreting those results requires context about dosage, timing, and individual response. Laboratory values alone do not automatically prove impairment; factors such as metabolism, tolerance, and medical conditions can affect how a medication shows up in blood or urine. The methods used by labs and the chain of custody for samples are also important considerations that can impact how the results are used in court. Challenging toxicology evidence often involves reviewing lab procedures, calibration records, and documentation of sample handling. Medical interpretation can explain whether measured levels are consistent with impairment at the time of driving. Because lab reports can be subject to procedural errors, careful review and, when appropriate, independent analysis can be a key part of defending against prescription drug DUI charges in Fayette.