Folate

Normal folate levels vary depending on the type of test performed and the laboratory conducting the analysis. For serum folate, normal levels are generally defined as above 4 ng/mL (above 9.1 nmol/L), while levels from 2-4 ng/mL (4.5-9.1 nmol/L) are considered borderline, and levels below 2 ng/mL (below 4.5 nmol/L) indicate deficiency [5].

Some laboratories use slightly different reference ranges, with normal serum folate levels reported as 2.7-17.0 ng/mL (6.1-38.4 nmol/L) for adults [5]. The variation in reference ranges emphasizes the importance of interpreting results within the context of the specific laboratory's standards.

For RBC folate, normal levels typically range from 140-628 ng/mL (317-1,422 nmol/L) for adults [5]. RBC folate concentrations are consistently higher than serum levels due to the concentration of folate within red blood cells. Deficiency is generally defined as RBC folate levels below 140 ng/mL (317 nmol/L) [1].

Pregnant women require higher folate levels to support fetal development and prevent neural tube defects. For pregnant individuals, serum folate levels should be maintained above 4.0 ng/mL (9.1 nmol/L) [5]. The recommended daily allowance (RDA) reflects these increased needs, with pregnant women requiring 600 mcg DFE (dietary folate equivalents) compared to 400 mcg DFE for non-pregnant adults [2].

It's important to note that reference ranges may vary between laboratories due to differences in testing methods and equipment. Healthcare providers should always interpret folate test results in conjunction with clinical symptoms and other laboratory findings to make accurate assessments of folate status and determine appropriate treatment recommendations.