Objectives Laboratory services are an important part of the healthcare system. However many requested tests may be considered inappropriate or unnecessary. We evaluated laboratory use in a period of 3 years in terms of the inappropriate test repeats. Methods We analyzed inappropriate repeat rate (IRR) of hemoglobin A1c (HbA1c), 25-OH vitamin D [25(OH)D], thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), free thyroxine (FT4), anti-thyroid peroxidase antibody (anti-TPO), vitamin B12, folate, iron, ferritin and total cholesterol in the light of clinical guidelines. Results IRR of 3 year was found to be 10% on average (4.2-15.5%). In TSH, FT3, and FT4 parameters, IRR was between 4.2 and 5.3%, while it was between 12.9 and 15.5% for 25(OH)D, iron, ferritin, and total cholesterol. In all tests (except anti-TPO), IRRs were found to be higher in inpatients for each of the 3 years. Inappropriate repetition of total cholesterol, iron, and ferritin parameters were more frequent in men. Inappropriate repeats were performed in all parameters (except HbA1c) after a result that had been in the reference range. Conclusions Examined test repetitions were mostly inappropriate. To reduce the inappropriate laboratory test requests, it is important to analyze the causes and to ensure cooperation between laboratory specialists and clinicians.