Vitamins
Folate (RBC or serum)
1-carbon donor; deficiency causes macrocytic anemia, neural tube defects, and homocysteinemia.
Sample
Serum or RBC
Clinical reference range
5 to 20 ng/mL
Serum
Conv: 5–20 ng/mL
Biology
What it measures
Reduced to tetrahydrofolate; cofactor in DNA synthesis and methionine metabolism.
Clinical use
Why we order it
Workup of macrocytosis; preconception and pregnancy supplementation (400–800 µg/day).
Differential
Causes of abnormal values
Causes of LOW
- ↓Inadequate intake
- ↓Alcoholism
- ↓Methotrexate, trimethoprim
- ↓Sulfasalazine
- ↓Phenytoin
Pitfalls
Pre-analytic & interpretation traps
- !Always replete B12 before folate to avoid masking neurologic deterioration of B12 deficiency.
Related