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 |
Agree on your personal target range with your doctor.
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 (few 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.
✓ What can influence this value
The folate value is influenced by intake through the diet (leafy vegetables such as spinach and broccoli, legumes, liver, oranges, avocado), preparations containing folic acid, alcohol consumption (can lower folate status), pregnancy, and diseases of the gut. Certain medications such as methotrexate or some antiepileptic drugs can disturb folate metabolism. Genetic variants such as the MTHFR polymorphism affect utilization, not necessarily the serum value. The assessment is made by the treating doctor.
When to test
Reasons for a measurement can include family planning and pregnancy, elevated homocysteine, a vegan diet, alcohol consumption, or MTHFR diagnostics. Whether and when it is measured is decided by your doctor. 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.
Why does folate matter in early pregnancy? +
The embryo's neural tube closes as early as weeks 4–6 of pregnancy, often before pregnancy is known. Folate deficiency is linked to neural tube defects. According to the US CDC (Folic Acid information page), folic acid can prevent some of these birth defects if supply is already in place before conception; starting only once the pregnancy is known can be too late for this early period. Whether and how folic acid is taken is decided by your doctor.
Does the MTHFR polymorphism have clinical significance for folate status? +
The common MTHFR C677T variant reduces enzyme activity. With adequate folate intake, carriers often show no clinical symptoms. Elevated homocysteine is the most sensitive functional indicator.
Can too much folic acid be harmful? +
Very high doses of synthetic folic acid can mask a B12 deficiency and delay recognition of neurological damage. Unmetabolized folic acid (UMFA) in the blood of MTHFR carriers is also debated. In 2023 EFSA set a tolerable upper intake level for folic acid and added folate forms from supplements and fortified foods; folate naturally present in food is not included (EFSA overview of tolerable upper intake levels, version 11, August 2025). It is based on the risk that a B12 deficiency goes unrecognised and neurological damage progresses. This is a safety limit, not an intake recommendation.
Folate (Vitamin B9)
Sources
Last updated: May 28, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.