Folate (folic acid)

What it measures

Measures folate, a B vitamin needed for DNA synthesis. Ordered with vitamin B12 in macrocytic anemia and to assess nutrition, especially in pregnancy and alcohol use.

Specimen and preparation

• Specimen: Serum (or EDTA whole blood for red cell folate)
• Tube: Gold top
• Preparation: Fasting sample preferred because a recent meal raises serum folate. Avoid hemolysis.

Reference range

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

• Folic acid supplements or fortified foods
• Vitamin B12 deficiency (folate trapping)
• Hemolyzed sample (red cell release)

Causes of low values

• Poor diet
• Alcohol use
• Malabsorption (celiac disease)
• Pregnancy and hemolytic anemias (higher demand)
• Drugs: methotrexate, phenytoin, trimethoprim

Method

Competitive immunoassay using folate-binding protein

Good to know

Red cell folate reflects stores over 2–3 months, while serum folate reflects recent intake. Treating folate deficiency without checking B12 can worsen neurological damage.

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