Blood levels of homocysteine, folate, vitamin B-6 and B-12 in women using oral contraceptives compared to non-users

Background and objectives: To compare the levels of total homocysteine (tHcy), folate, vitamin B-6 and B-12, in women not using oral contraceptives (OC) vs. those using OC. Materials and methods: 219 healthy women were enrolled in the study; 159 of them had not been using OC for at least 12 months prior to their enrolment, while 60 were on regular OC treatment. Results: The median levels of vitamin B-6 and B-12 were significantly lower in OC users than in non-users (24.2 vs. 32.9 nmol/l, p = 0.029; 278 vs. 429 ng/ml, p < 0.001). There were no statistically significant differences in the levels of tHcy (fasting and post-methionine loading) and folate. Conclusions: In our cross-sectional study, OC use was associated with low vitamin B-6 and B-12 levels. Since low vitamin B-6 levels are independently associated with heightened risks for arterial and venous thromboembolism (TE), they could partly account for the increased TE risk of OC users.