Background: Methylenetetrahydrofolate reductase (MTHFR) polymorphisms may cause various medical disorders through different mechanisms. We aimed to determine the allelic frequency and the prevalence of homozygous MTHFR polymorphisms in a tertiary university hospital population that necessitated MTHFR polymorphism investigation owing to various reasons. Methods: Our study consisted of 10449 patients who necessitated MTHFR polymorphism investigation owing to various reasons (coronary artery diseases, thrombotic events, epilepsy, migraine, repeated miscarriages, various obstetric complications) during 2008-2017. Results: The allelic frequency of MTHFR 677 and MTHFR 1298 mutations were 0.296 and 0.283 respectively. The prevalence of homozygous MTHFR C677T and MTHFR A1298C polymorphisms were 10.2 % and 11.1 %, respectively. Conclusion: MTHFR polymorphisms are more frequent than was expected and one should be cautious when drawing disorder specific conclusions.