Type the folate from your lab report — serum or red blood cell — and, if the same report prints it, the vitamin B12. You see the folate against the lines NIH ODS, MedlinePlus and the WHO print, what those sources say lowers it, and the B12 beside it. Your lab’s own range and your doctor have the last word.
Serum folate 10 ng/mL is
Above all four low lines 10 ng/mL = 22.7 nmol/L
Serum folate 10 ng/mL: above NIH ODS’s adequacy line (“above 3 ng/mL”); inside MedlinePlus’s 2.7–17.0 ng/mL range; not under WHO’s 2005 deficiency cut-off (under 4 ng/mL); in the “normal range” band of WHO’s 1968 table.
That is above every low line the sources print. The range on your own lab report is the one your doctor reads it against.
What the sources say about it
- MedlinePlus: “Normal value ranges may vary slightly among different labs. Talk to your provider about the meaning of your test results.”
- NIH ODS: “This indicator, however, is sensitive to recent dietary intake, so it might not reflect long-term status.”
MMA, the test that confirms a low B12, and where a B12 alone sits: the Vitamin B12 Level Checker.
| Source | Serum folate | Red blood cell folate |
|---|---|---|
| NIH ODS (adequacy) | Above 3 ng/mL (6.8 nmol/L, converted) | Above 140 ng/mL (317.1 nmol/L, converted) |
| MedlinePlus (normal range) | 2.7–17.0 ng/mL (6.12–38.52 nmol/L) | none printed |
| WHO 2005 (deficiency, by homocysteine) | Under 4 ng/mL (10 nmol/L) | Under 151 ng/mL (340 nmol/L) |
| WHO 1968 (by anaemia) | Deficiency under 3; possible deficiency 3–5.9; normal 6–20; elevated over 20 ng/mL | Deficiency under 100 ng/mL (226.5 nmol/L) |
| WHO 2015 (women of reproductive age, population level) | none set | Sufficiency above 400 ng/mL (906 nmol/L) |
This is not medical advice and it does not diagnose anything. It shows where a number sits against published lines; what your result means for you depends on your lab, your B12, your blood count, your history and your doctor.
MedlinePlus prints a normal serum folate of 2.7 to 17.0 ng/mL (6.12 to 38.52 nmol/L). NIH ODS says a serum folate “above 3 ng/mL indicates adequacy”, and a red blood cell folate “above 140 ng/mL indicates adequate folate status”. The WHO’s deficiency cut-offs are under 4 ng/mL in serum and under 151 ng/mL in red cells. Your lab’s printed range comes first.
How to use it
Pick the test your report shows — serum (or plasma) folate, or red blood cell folate — type the number and say whether it is printed in ng/mL, mcg/L (the same number) or nmol/L. If the same report prints a vitamin B12, type it too. You see the folate against each line the sources print, how many of the low lines it is under, what the sources say lowers it, and the B12 beside it with the reason the two are read together. It does not diagnose anything: it places a number and quotes the sources.
Serum folate or red blood cell folate?
NIH ODS: “Serum folate concentrations are commonly used to assess folate status; a value above 3 ng/mL indicates adequacy”. “This indicator, however, is sensitive to recent dietary intake, so it might not reflect long-term status.” “Erythrocyte folate concentrations provide a longer term measure of folate intakes; a concentration above 140 ng/mL indicates adequate folate status”. Erythrocyte means red blood cell. MedlinePlus calls the blood test “Folic acid – test” and adds: “It is often done together with a vitamin B12 test of the blood.”
The lines the sources print
| Source | Serum folate | Red blood cell folate |
|---|---|---|
| NIH ODS (adequacy) | Above 3 ng/mL (6.8 nmol/L, converted) | Above 140 ng/mL (317.1 nmol/L, converted) |
| MedlinePlus (normal range) | 2.7–17.0 ng/mL (6.12–38.52 nmol/L) | none printed |
| WHO 2005 (deficiency, by homocysteine) | Under 4 ng/mL (10 nmol/L) | Under 151 ng/mL (340 nmol/L) |
| WHO 1968 (by anaemia) | Deficiency under 3; possible deficiency 3–5.9; normal 6–20; elevated over 20 ng/mL | Deficiency under 100 ng/mL (226.5 nmol/L) |
| WHO 2015 (women of reproductive age, population level) | none set | Sufficiency above 400 ng/mL (906 nmol/L) |
MedlinePlus (reviewed 2/3/2025): “The normal range is 2.7 to 17.0 nanograms per milliliter (ng/mL) or 6.12 to 38.52 nanomoles per liter (nmol/L).” “Normal value ranges may vary slightly among different labs. Talk to your provider about the meaning of your test results.” The WHO’s three tables come from its 2015 summary, Serum and red blood cell folate concentrations for assessing folate status in populations, which prints its own factor: “Folic acid conversion factor: 1 ng/mL = 2.265 nmol/L.” mcg/L on a report is the same number as ng/mL.
What the WHO’s lines are for
The WHO’s lines were set for populations, and the WHO says what each is not. On “elevated” in its 1968 table: “It should be noted that folate concentrations defined as “elevated” were based on the assay’s upper-limit capabilities without dilutions, and not on the biological implications for health.” On its 2005 cut-offs: “These values apply to all age groups, although the consultation recognized that the values may not be appropriate to assess folate status in pregnant women, since folate concentrations typically decline during pregnancy, nor are they adequate thresholds for the prevention of NTDs”. And on its 2015 red-cell line of 400 ng/mL for women who could become pregnant: “These thresholds should not be used at an individual level for determination of risk of a neural tube defect-affected pregnancy.” The test method matters too: “Protein-binding assays were found to be less accurate, with one measuring ~30% lower concentrations of red blood cell folate and serum folate relative to the microbiological assay and liquid chromatography-tandem mass spectrometry (LC-MS/MS)”.
What lowers it
MedlinePlus: “Lower-than-normal folic acid levels may indicate: Poor diet; Malabsorption syndrome (for example, celiac disease); Malnutrition”. “Medicines that can decrease folic acid measurements include: Alcohol; Aminosalicylic acid; Birth control pills; Estrogens; Tetracyclines; Ampicillin; Chloramphenicol; Erythromycin; Methotrexate; Penicillin; Aminopterin; Phenobarbital; Phenytoin; Medicines to treat malaria”. NIH ODS: “Isolated folate deficiency is uncommon; folate deficiency usually coexists with other nutrient deficiencies because of its strong association with poor diet, alcoholism, and malabsorptive disorders”. On alcohol: “Even moderate alcohol consumption of 240 ml (8 fluid ounces) red wine per day or 80 ml (2.7 fluid ounces) vodka per day for 2 weeks can significantly decrease serum folate concentrations in healthy men, although not to levels below the cutoff for folate adequacy of 3 ng/ml”. On epilepsy medicines: “These medications can reduce serum folate levels”.
Folate and vitamin B12 are read together
NIH ODS gives the reason: “Large amounts of folate can correct the megaloblastic anemia, but not the neurological damage, that can result from vitamin B12 deficiency.” Its B12 fact sheet reports one survey of older adults: “For example, an analysis of cross-sectional 2011–2014 NHANES data on 2,420 adults age 60 years or older found that low vitamin B12 (MMA greater than 0.27 micromol/L or serum vitamin B12 less than 203 pg/mL [150 pmol/L]) combined with high folic acid—unmetabolized serum folic acid greater than 0.44 mcg/L (1 nmol/L) or serum total folate higher than 32.7 mcg/L (74.1 nmol/L)—was associated with an almost two to three times higher risk of cognitive impairment”. That is an association in a survey. The checker shows it only when both of its conditions hold, and places the B12 against the same lines the Vitamin B12 Level Checker uses.
Before the blood draw
MedlinePlus: “You should not eat or drink for 6 hours before the test.” “Your health care provider may tell you to stop taking any medicines that may interfere with test results, including folic acid supplements.” Ask the person who ordered the test before stopping anything.
Worked examples
- Serum 10 ng/mL (the page’s example): above all four low lines, inside MedlinePlus’s range, in WHO 1968’s “normal range” band.
- Serum 3 ng/mL: not above ODS’s “above 3” — the line itself is not above it — inside MedlinePlus’s range from 2.7, under WHO’s 4 and in WHO 1968’s “possible deficiency” band: under 3 of the 4 low lines.
- Serum 25 ng/mL: above MedlinePlus’s 17.0 and in WHO 1968’s “elevated” band — with WHO’s sentence that “elevated” was the assay’s limit, not a health line.
- Red blood cell 300 ng/mL: above all three low lines; under WHO’s 2015 population line of 400 for women who could become pregnant, which the WHO says is not for individuals.
- Serum 40 ng/mL with a B12 of 180 pg/mL: the folate is above MedlinePlus’s range and the B12 under both of ODS’s subnormal lines, so ODS’s NHANES sentence is shown.
Common mistakes
- Reading a serum folate as a long-term measure. ODS: it “might not reflect long-term status”. Red cell folate does.
- Comparing a red cell folate with a serum range. Red cell numbers run in the hundreds; serum in single and low double figures.
- Treating mcg/L as a different unit. It is the same number as ng/mL.
- Reading folate without the B12. ODS: folate “can correct the megaloblastic anemia, but not the neurological damage, that can result from vitamin B12 deficiency.”
- Using the WHO’s 400 ng/mL as a personal pregnancy test. The WHO says it should not be used at an individual level.
Frequently asked questions
What is a normal folate level?
MedlinePlus prints 2.7 to 17.0 ng/mL (6.12 to 38.52 nmol/L) for serum folate. NIH ODS calls a serum folate above 3 ng/mL, and a red blood cell folate above 140 ng/mL, adequate. Your lab’s printed range is the one your doctor uses.
What does a folate blood test show?
How much folate is in your blood. A serum test follows the last few days’ meals — ODS: it “is sensitive to recent dietary intake” — and a red blood cell test gives “a longer term measure of folate intakes”.
What level of folate is deficient?
The WHO’s 2005 cut-offs for deficiency are under 4 ng/mL (10 nmol/L) in serum and under 151 ng/mL (340 nmol/L) in red blood cells. Its older 1968 table puts deficiency under 3 ng/mL in serum and under 100 ng/mL in red cells. What a low result means for you is your doctor’s reading, with your B12 and blood count.
What does high folate mean?
MedlinePlus’s range ends at 17.0 ng/mL. The WHO’s 1968 table calls over 20 ng/mL “elevated”, and adds that this was based on “the assay’s upper-limit capabilities without dilutions, and not on the biological implications for health.” A high folate is read with your B12 and what you take.
Do I need to fast for a folate blood test?
MedlinePlus: “You should not eat or drink for 6 hours before the test.”
Why are folate and B12 tested together?
NIH ODS: “Large amounts of folate can correct the megaloblastic anemia, but not the neurological damage, that can result from vitamin B12 deficiency.” MedlinePlus: “It is often done together with a vitamin B12 test of the blood.”
How do you convert folate from ng/mL to nmol/L?
Multiply by 2.265 — the WHO’s “Folic acid conversion factor: 1 ng/mL = 2.265 nmol/L.” 10 ng/mL is 22.7 nmol/L.
More blood-test checkers: the Vitamin B12 Level Checker, the MCV Level Checker, the Hemoglobin Level Checker, the Ferritin Level Checker and the Homocysteine Level Checker, the line NIH ODS reads beside folate. Folate’s RDA and upper limit for your age: the Vitamin & Mineral Dose Lookup. A supplement label’s folic acid or methylfolate in mcg DFE: the Folate vs Folic Acid (DFE) Calculator.
Read next
- Vitamin B9 — folate, what it does and where it comes from.
- Folic acid for women and men
- Vitamin B12 as a nootropic — the vitamin folate is read with.
- The best vitamins for women at 30+
This is not medical advice, and nothing here diagnoses or treats anything. It shows where a number sits against published lines and quotes what the sources say about it; your lab’s own range, your B12, your blood count, your history and your doctor decide what it means. Some links on this site are affiliate links: I buy what I review at full price, and a commission never changes a verdict.