Objectives An important risk factor for the occurrence of side effects during azathioprine treatment is the Genotipizacija TPMT), a metabolic enzyme responsible for the balance between the therapeutic and cytotoxic effects of thiopurine. The aim of this paper is to present the situation in the implementation of TPMT genotyping in the Croatian population, that is to determine the frequency of variant alleles (TPMT*2, *3A, *3C) responsible for the reduced TPMT activity. Also, the aim is to present the distribution of TPMT gene polymorphisms by age and sex and the distribution of requirements for TPMT analysis according to the level of health care (primary, secondary, tertiary). Material and Methods The research was conducted in the Department of Pharmacogenomics and Individualization of Therapy at the Clinical Institute for Laboratory Diagnostics of the Clinical Hospital Center Zagreb. The results of 494 received requests for routine TPMT genotyping in patients with inflammatory bowel disease in 2019 were analyzed. Data obtained from TPMT genotyping were analyzed retrospectively. Genotyping was performed from a 3 ml blood sample in a Na-EDTA tube. Genotyping of TPMT*2, TPMT*3B and TPMT*3C polymorphisms was performed by the TaqMan® real-time polymerase chain reaction method for detection and analysis of single nucleotide polymorphisms. Determination of polymorphisms was performed on a real-time PCR device by allelic discrimination analysis. Results The wild genotype was found in 93,9 % of the examined samples, and 6,07 % were heterozygous and harbored polymorphisms. The most commonly reported variant genotype was TPMT*1/*3A (5,9 %), and a variant genotype TPMT*1/*3C was found in one patient. Most patients were referred for testing by a selected primary care physician, as recommended by a gastroenterologist. This is followed by the frequency of requests from tertiary institutions - clinical hospitals and clinical hospital centers, and requests from general hospitals and institutions of the secondary level of health care. Conclusion The results of this research coincide with the results of previous research conducted in the Croatian population. The frequency of variant genotypes is similar to that in other European populations. Genotyping TPMT is a useful tool for screening patients with inflammatory bowel disease who have an increased risk of myelotoxicity, when standard doses of azathioprine are administered. In individuals who are heterozygous or homozygous for the mutant allele and therefore have reduced TPMT enzyme activity, the starting dose as well as further dose titration should be adjusted.