The effect of medication on laboratory test results.

It is becoming common practice to order the SMA-12 battery or a similar group of blood chemistry tests on middle-aged or elderly adults who are under medical care. Test result abnormalities are often found. Their significance is not always obvious. In a survey of more than 2500 adult hospital admissions the incidence of abnormal test results was determined in patients with and without disease, receiving or not receiving 42 commonly administered medications. It was concluded that very few medications affect laboratory test results and that they do so only to a minimal extent or only in a few unusually idiosyncratic patients. Combinations of medication are also without effect. In the majority of cases, test result abnormalities should not be ascribed to a patient’s medication but to his underlying disease or metabolic state. In particular, elevations of serum uric acid correlate better with the presence of congestive heart failure or hypertension than they do with the ingestion of thiazide drugs.