Statin-treated patients undergo frequent laboratory tests. This study evaluated the clinical impact of abnormal liver or muscle enzyme results.This clinical process evaluation study took place in six primary care clinics in Israel. Four hundred and eight patients (average age 63.8 ± 10.9 years) undergoing statin treatment, with at least one enzyme level > 10% normal, were categorized by symptomatology possibly related to statins. Aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase and creatine phosphokinase were measured. Management and etiology of the elevation were assessed.Changes in statin regimen.Thirty-six (8.8%) patients were symptomatic at the index encounter. One enzyme was elevated in 74.8%. Patients experiencing side effects had more repeat tests (36.1 vs 17.7%, p < 0.001). Musculoskeletal symptoms resulted in a change in treatment more than digestive symptoms did (73.3 vs 16.7%, p < 0.001). Of 40 (9.8%) patients who had additional evaluation, two symptomatic patients had treatment changes.There is little practical value in routine follow-up enzyme tests for patients on statins. Our findings strengthen reports that recommend muscle and liver enzyme tests for symptomatic patients only.