Background. The data on vitamin D (VD) supplementation rationales and rates among undergraduates of medical universities is limited. We aimed to investigate the rate of students who declare VD supplementation, and factors that influence the decision on VD supplementation. Material and methods. A cross-sectional survey study among medical university students was performed from November 2018 through April 2019. The anonymous questionnaire contained questions about VD supplementation, persons from a student environment, who supplement or recommend VD intake, the most important personal rationale for initiation of or resignation from VD supplementation, the daily dose of VD, the period of supplementation, sex, BMI category, and age. In statistical analysis logistic regression analysis was performed. Results. A total of 595 completed surveys were collected. 303 (50.9%) of the respondents declared VD supplementation. The main personal rationales for VD intake were: knowledge acquired during the studies – 153 (52.1%), knowledge gained beyond the studies – 45 (14.9%), and medical specialist recommendation – 34 (11.2%). The main reasons for resignation from VD supplementation were: lack of motivation – 199 (68.2%), considering the supplementation as a waste of money – 20 (6.8%), and personal belief in little significance of VD for health – 14 (4.8%). VD supplementation was positively associated with studying in the medicine faculty (OR, 95% CI: 1.89, 1.33–2.68), family doctor’s recommendation (1.82, 1.05–3.14), and medical specialist’s recommendation (4.03, 2.15–7.54), and negatively related to friends’ recommendations (0.58, 0.38–0.90). Conclusion. Half of the undergraduates declared VD supplementation. Studying in the medicine faculty and physician’s recommendations were positively associated with VD intake. VD supplementation should be promoted among students.