Folate
Also known as: Folic Acid, Vitamin B9
What Does Folate Measure?
Folate, also known as vitamin B9, is a water-soluble B vitamin that the body uses to make and repair DNA, produce red blood cells, and support cell division. A blood folate test measures the level of folate circulating in your bloodstream, and can be measured either as serum folate (reflecting recent dietary intake) or red blood cell (RBC) folate (reflecting longer-term folate status over the past 2-3 months). The test is typically reported in nanograms per milliliter (ng/mL) or nanomoles per liter (nmol/L).
Why Does Folate Matter?
Adequate folate levels are essential for healthy cell growth and function throughout the entire body. It plays a critical role in the synthesis of nucleotides — the building blocks of DNA — making it especially important during periods of rapid cell division such as pregnancy, infancy, and adolescence. Folate deficiency can lead to megaloblastic anemia, where red blood cells become abnormally large and dysfunctional, causing fatigue, weakness, and shortness of breath. Perhaps most critically, insufficient folate during early pregnancy significantly increases the risk of neural tube defects such as spina bifida and anencephaly in the developing fetus. Folate also works alongside vitamin B12 to regulate homocysteine levels, and chronically elevated homocysteine is associated with increased risk of cardiovascular disease and cognitive decline.
Normal Ranges
Males
2.7–17.0 ng/mL (serum); RBC folate: 140–628 ng/mL
Females
2.7–17.0 ng/mL (serum); RBC folate: 140–628 ng/mL
Children
Varies by age; generally 2.0–17.0 ng/mL for children over 1 year
Causes of High Levels
- High dietary intake of folate-rich foods such as leafy greens, legumes, and fortified cereals
- Folic acid supplementation or multivitamin use containing high-dose B9
- Vitamin B12 deficiency, which can cause serum folate to appear elevated due to impaired cellular uptake
- Folate injections or intravenous supplementation used in medical treatment
- Recent consumption of a meal high in folate shortly before blood draw (affects serum folate specifically)
Causes of Low Levels
- Poor dietary intake of folate-rich foods, common in restrictive diets or food insecurity
- Alcohol use disorder, which impairs folate absorption and increases urinary excretion
- Malabsorption disorders such as celiac disease, Crohn's disease, or inflammatory bowel disease
How to Improve Your Folate
Diet
- Eat dark leafy greens daily — spinach, romaine lettuce, kale, and asparagus are among the richest natural sources (1 cup cooked spinach provides ~263 mcg folate)
- Include legumes such as lentils, black beans, and chickpeas regularly (1 cup cooked lentils provides ~358 mcg folate)
- Choose fortified foods such as breakfast cereals, enriched bread, and pasta, which have folic acid added by law in many countries
- Add avocado to meals — one medium avocado provides approximately 163 mcg of folate
- Minimize alcohol consumption, as alcohol significantly inhibits folate absorption and accelerates its breakdown
Supplements
- Folic acid 400–800 mcg/day is the standard recommended dose for most adults; women planning pregnancy should take 400–800 mcg daily
- L-methylfolate (5-MTHF) at 400–1,000 mcg/day is the active, bioavailable form — preferred for individuals with MTHFR gene variants who cannot efficiently convert folic acid
- Prenatal vitamins typically contain 400–800 mcg of folic acid and are recommended before and during pregnancy
- B-complex vitamins containing folate alongside B12 and B6 can support overall B-vitamin metabolism and homocysteine regulation
Related Biomarkers
Frequently Asked Questions
What is the difference between folate and folic acid?
Folate is the naturally occurring form of vitamin B9 found in whole foods like leafy greens, beans, and citrus fruits. Folic acid is the synthetic form used in dietary supplements and added to fortified foods. While both serve the same fundamental purpose, folic acid must be converted by the body into its active form (5-methyltetrahydrofolate or 5-MTHF) before it can be used. People with MTHFR gene mutations may have reduced ability to make this conversion efficiently, making the active form L-methylfolate a better supplementation choice for them.
Why is folate so important during pregnancy?
Folate is critical during the first 28 days of pregnancy — often before a woman even knows she is pregnant — because it is essential for the proper closure of the neural tube, which develops into the baby's brain and spinal cord. Insufficient folate at this stage can lead to neural tube defects such as spina bifida (incomplete spinal cord closure) or anencephaly (absence of a major portion of the brain). Most health authorities recommend that all women of childbearing age consume at least 400 mcg of folic acid daily, increasing to 600 mcg during pregnancy.
Can you have normal folate but still have a deficiency?
Yes, this is possible. Serum folate reflects your intake over just the past few days and can appear normal even when your body's stored folate is low. Red blood cell (RBC) folate is a more reliable indicator of long-term folate status, as it reflects folate levels over the past 2–3 months. Additionally, people with MTHFR gene mutations may have 'normal' folate levels in blood tests but still have functional folate deficiency because their body cannot convert it into the active form efficiently, leading to elevated homocysteine despite seemingly adequate folate.