Background This investigation determines the nutritional state of serum and red blood cell (RBC) folate concentration and their relation with intake of folate, B 6 ,and B 12 , with serum vitamin B 12 , and with genetic variants after provision of 400 μg/day of folic acid for 3 months to a group of 34 Colombian women of reproductive age. Methods We evaluated nutrient intake using 24‐hr recall, assessing the levels of serum folate, RBC folate, serum B 12 , and homocysteine, as well as determining genetic variants of the enzyme MTHFR (C677T and A1298C) and CβS (844ins68pb). Results The results show that following intake of 400 μg/day of folic acid, the risk of folate deficiency as seen in regular dietary intake disappears and the nutritional status of this nutrient is increased ( p < 0.001). With respect to vitamin B 12, the risk of serum deficiency with folic acid consumption increased slightly, and those that were found to be B 12 deficient after supplementation also had decreased levels of serum homocysteine. Genetic factors did not influence the nutritional status of folate, although an association was found between the intake of nutrients and biochemical indicators. Conclusion Given the results of our study, subsequent studies evaluating folic acid supplementation should also consider evaluating the status of B 12 and B 6 , and serum and RBC folate, as they participate interdependently in the cycle of folate and methionine and in homocysteine metabolism.Birth Defects Research 109:564–573, 2017.© 2017 Wiley Periodicals, Inc.