Supplementing with folic acid in amounts as little as 300 to 800 mcg per day may increase vitamin B12 requirements. Therefore, it would be prudent for people taking folic acid to supplement with vitamin B12.
Supplementation with vitamin B12, even in relatively small amounts, can increase folic acid requirements, For that reason, people taking vitamin B12 supplements should also consider taking folic acid.
In addition, supplementing with folic acid can mask the laboratory diagnosis of vitamin B12 deficiency. Failure to identify and treat vitamin B12 deficiency in a timely manner can lead to permanent neurological damage. The relatively small amount of vitamin B12 present in most supplements is not sufficient to prevent or correct vitamin B12 deficiency in people who have pernicious anemia (a condition caused by vitamin B12 malabsorption). For that reason, people should tell their doctor if they are taking folic acid supplements, so that the doctor will order alternative laboratory tests if vitamin B12 deficiency is suspected.
- Smith AD. Folic acid fortification: the good, the bad, and the puzzle of vitamin B-12. Am J Clin Nutr 2007;85:3-5.
- Steiner I,Melamed E. Folic acid and the nervous system. Neurology. 1983 Dec;33(12):1634