Folate (Vitamin B9)
B vitamin for DNA synthesis, cell growth, and homocysteine breakdown
Also known as
Definition
Folic acid (synthetic form) or folate (natural form in foods) is a water-soluble B vitamin essential for DNA synthesis, cell division, and methylation reactions. Particularly important during pregnancy (neural tube defect prevention) and with elevated homocysteine. The MTHFR polymorphism impairs conversion of folic acid to the active form (methyltetrahydrofolate).
| Parameter | Value |
|---|---|
| Unit | nmol/l (ng/ml) |
| Reference Range | 7–45 nmol/l (serum); red blood cell folate: 360–900 nmol/l |
| Optimal Range (lab2go) | > 20 nmol/l serum (lab2go Optimum Zone; RBC folate > 500 nmol/l for tissue supply) |
Conversion: 1 ng/ml = 2.266 nmol/l. US labs use ng/ml (normal value 2.7–17 ng/ml).
↓ What a low value means
Low folate indicates inadequate intake (little vegetables/legumes), alcohol abuse, malabsorption, MTHFR polymorphism, or elevated demand (pregnancy). Consequences: megaloblastic anemia, elevated homocysteine, neural tube defects in fetuses, increased depression risk.
↑ What a high value means
Very high folate values typically result from supplementation and are harmless for most people. Uncontrolled high synthetic folic acid intake can mask a B12 deficiency and in individuals with the MTHFR variant may lead to unmetabolized folic acid (UMFA) in the blood.
✓ How to optimize this marker
Dietary sources: leafy vegetables (spinach, broccoli), legumes, liver, oranges, avocado. Supplementation: 400 µg/day (preventive), 800 µg/day (pregnancy). With MTHFR polymorphism: prefer 5-MTHF (active methylfolate). Alcohol reduction significantly improves folate status.
When to test
For family planning/pregnancy (before conception), elevated homocysteine, vegan diet, alcohol consumption, or MTHFR diagnostics. Red blood cell folate reflects long-term status (3 months) better than serum folate.
Frequently asked questions
What is the difference between folic acid and folate? +
Folate is the natural umbrella term for all forms of vitamin B9 in foods. Folic acid is the synthetic, oxidized form found in supplements and fortified foods. Folic acid must be converted in the body to active 5-MTHF — a step that is impaired with MTHFR polymorphisms.
When should I start folic acid in pregnancy? +
At least 4 weeks before conception and through the end of the first trimester (week 12). The neural tube closes as early as weeks 4–6 of pregnancy, often before pregnancy is known. Major health agencies recommend 400 µg daily in addition to dietary intake.
Does the MTHFR polymorphism have clinical significance for folate status? +
The common MTHFR C677T variant reduces enzyme activity by 30–70%. Carriers may benefit from active 5-MTHF instead of folic acid, but with adequate folate intake often show no clinical symptoms. Elevated homocysteine is the most sensitive functional indicator.
Can too much folic acid be harmful? +
Excessively high synthetic folic acid doses (> 1,000 µg/day) can mask a B12 deficiency and delay recognition of neurological damage. Unmetabolized folic acid in blood in MTHFR carriers is a debated concern. EFSA sets the tolerable upper limit for synthetic folic acid at 1,000 µg/day.
Sources
Last Reviewed: May 28, 2026 · sina
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.