From the Guidelines
A healthy erythrocyte (Red Blood Cell) folate level for adult females is above 340 nmol/L, which is equivalent to approximately 140-160 ng/mL, considering the molecular weight of folate. This recommendation is based on the most recent and highest quality study available, which suggests that serum folate levels should be 10 nmol/L and red blood cell folate 340 nmol/L 1. It is essential to note that folate status is conventionally assessed by measuring levels of folate in serum/plasma or RBC, with RBC folate being a sensitive marker of long-term folate status.
Some key points to consider:
- Folate is crucial for DNA synthesis, cell division, and proper neural tube development during pregnancy, making adequate levels particularly important for women of childbearing age.
- Low folate levels can lead to megaloblastic anemia, while pregnant women with insufficient folate face increased risk of neural tube defects in their babies.
- The RBC folate test is preferred over serum folate as it reflects long-term folate status rather than recent dietary intake.
- Certain medications, such as anticonvulsants and methotrexate, can deplete folate, so women taking these medications may need higher supplementation 1.
In terms of measurement, plasma/serum and whole blood folate concentrations can be measured by a microbiological assay (MBA) using Lactobacillus rhamnosus, which is viewed as the gold standard technique for folate status assessment 1. However, it is crucial to follow pre-analytical precautions to ensure reliable results, such as using ascorbic acid to protect folate from oxidation.
Overall, maintaining adequate folate levels is vital for optimal health, particularly for women of childbearing age, and RBC folate levels above 340 nmol/L (approximately 140-160 ng/mL) are recommended 1.
From the FDA Drug Label
Normal erythrocyte folate levels have been reported to range from 175 to 316 ng/mL.
A healthy erythrocyte (Red Blood Cell) folate level for adult females is between 175 and 316 ng/mL 2.
From the Research
Healthy Erythrocyte Folate Levels
- A healthy erythrocyte (Red Blood Cell) folate level in adult females is generally considered to be above 400 ng/mL 3, 4, 5.
- Studies have shown that red cell folate levels higher than 906 nmol/L (400 ng/mL) may be optimal for the prevention of folate-responsive neural tube defects 3.
- The median red blood cell (RBC) folate level of the U.S. population 4 years of age and older was 266 ng/mL in 2005-2006, with a prevalence of low RBC folate (less than 140 ng/mL) among U.S. women of childbearing age (15-45 years) of 4.5% 4.
- A study in Belgium found that the median RBC folate concentration was 436 ng/ml among first trimester and 496 ng/ml among third trimester women, with 39% of women in the first trimester having a RBC concentration below 400 ng/ml 5.
Factors Influencing Folate Levels
- Folic acid supplements, folic acid intake from fortified cereals, vitamin C supplements, and serum zinc level (inverse) were found to predict red cell folate levels 3.
- The use of folic acid supplements was associated with higher red cell folate levels, with 69.1% of women in the first trimester reporting taking folic acid-containing supplements 5.
- Folate status increased significantly with education level and was significantly higher among women who planned the pregnancy and who did not smoke 5.
Measurement of Folate Levels
- The accuracy of RBC folate assays remains a concern, with different assays yielding different results 6.
- A study comparing four different assays found that baseline RBC folate levels ranked low to high by assay, with supplementation raising RBC folate levels to varying degrees depending on the assay used 6.