Effect of storage on serum vitamin B12 and folate stability.

To facilitate transport from remote locations, the stability of vitamin B12 and folate was investigated in serum specimens. Serum vitamin B12 proved to be highly unstable, emphasizing that specimens should be frozen if not analyzed immediately. Light protection is necessary if the sample cannot be analyzed within 4 hours. In contrast, folate is a more robust analyte. In refrigerated serum specimens, folate was stable up to 7 days of storage. In situations where specimen stability is important, vitamin B12 status is better assessed with serum or urine methylmalonic acid measurements. Although folate status can be assessed in a similar fashion with homocysteine, specimen stability indicates that direct measurement of folate is a better strategy.