Quick answer: on a folate blood test, MedlinePlus gives a normal serum folate of 2.7 to 17.0 ng/mL (6.12 to 38.52 nmol/L). The NIH Office of Dietary Supplements says serum folate above 3 ng/mL indicates adequacy, and red blood cell (RBC) folate above 140 ng/mL indicates adequate longer-term status. Serum folate swings with what you ate recently, so MedlinePlus asks for 6 hours without food or drink before the test.
Folate normal range
| Test | Value | Meaning | Source |
|---|---|---|---|
| Serum folate | 2.7 to 17.0 ng/mL (6.12 to 38.52 nmol/L) | Normal range | MedlinePlus |
| Serum folate | Above 3 ng/mL (about 6.8 nmol/L) | Adequate | NIH ODS |
| RBC folate | Above 140 ng/mL | Adequate longer-term status | NIH ODS |
To convert ng/mL to nmol/L, multiply by 2.266. Labs vary slightly, so read your result against the range on your report.
MedlinePlus. The NIH treats a serum folate above 3 ng/mL (about 6.8 nmol/L) as adequate. To convert, multiply ng/mL by 2.266.
What is folate?
Folate (vitamin B9) is needed to make DNA and new cells, including red blood cells. It is found in leafy greens, beans and citrus, and as folic acid in supplements and fortified grain products. Low folate causes the same kind of anemia as low vitamin B12, with large, immature red cells, which is why the two are tested together. Folate also matters before and in early pregnancy for the baby's development.
Serum folate or RBC folate?
Serum folate is the common test and the one most panels include. The NIH notes it is sensitive to recent intake, so one folate-rich meal or supplement can lift it even if your stores are low. RBC folate, measured inside red cells, is the NIH's longer-term measure of intake, but fewer labs offer it. If a serum result is borderline, ask your doctor whether an RBC folate or a B12 check is the better next step.
What low folate means
Low folate can lead to anemia and tiredness. MedlinePlus lists these causes:
- Poor diet with too few folate-rich foods
- Malabsorption, for example from celiac disease
- Conditions that increase needs, such as pregnancy
- Medicines that interfere with folate, including some antiepileptic drugs and some antibiotics
Cleveland Clinic adds alcohol use disorder, kidney dialysis, hemolytic anemia, some skin conditions and medicines for seizures, infections or immune disorders, and notes that people 60 and older are more likely to be low. Because low B12 and low folate look alike on a blood count, a doctor will usually check both.
How to read your folate result
- Check whether you fasted. A meal or supplement beforehand can lift serum folate into the normal range.
- Compare with 3 ng/mL. The NIH treats above 3 ng/mL as adequate; your lab's lower limit may be 2.7.
- Read it with B12. Low folate and low B12 cause the same anemia, so both need checking.
- Consider RBC folate if the serum value is borderline and you want a longer-term picture.
Worked example: folate of 3.4 before pregnancy
Say a 31-year-old woman planning a pregnancy gets a fasting serum folate of 3.4 ng/mL (about 7.7 nmol/L). It is inside the MedlinePlus normal range of 2.7 to 17.0 and above the NIH adequacy line of 3 ng/mL, but only by 0.4. Because serum folate reflects recent intake, a week of low-folate meals could explain it as easily as low stores.
What might explain it: a diet light on leafy greens, beans and fortified grains, or, less often, malabsorption such as celiac disease (MedlinePlus).
Questions to take to her doctor:
- Should I start folic acid now, and at what dose, since I am planning a pregnancy?
- Would an RBC folate (adequate above 140 ng/mL, per NIH) give a clearer picture of my stores?
- Should my B12 be checked before I take folic acid?
What high folate means
MedlinePlus does not set a clinical meaning for a high serum folate. In practice, a result above the range usually reflects recent intake, often from supplements or fortified foods, since the NIH notes serum folate tracks recent intake. It is rarely a problem in itself, but if you take high-dose folic acid, make sure your B12 has been checked too.
What moves folate
- Food: leafy greens, beans, lentils and fortified cereals.
- Supplements: folic acid raises serum folate quickly. People who could become pregnant are commonly advised to take folic acid; ask your doctor what applies to you.
- Alcohol and medicines: alcohol use disorder and some drugs lower folate (Cleveland Clinic). Do not stop a prescribed medicine without advice.
- Timing: a meal or a supplement before the test raises the serum value, so fast as instructed.
Folate blood test: how to prepare
MedlinePlus says not to eat or drink for 6 hours before the test, and to tell your provider about medicines such as birth control pills, some antibiotics and antiepileptic drugs. You may be told to stop folic acid supplements before the test; only do so if your provider says so. Test with B12 and a blood count if you are investigating anemia or fatigue.
Which at-home tests include folate
Folate is on two SiPhox panels: Ultimate 360 and GLP Optimization. The four included core panels do not measure it.
| SiPhox panel | Biomarkers per test | Per test, with shipping | Listed as |
|---|---|---|---|
| Ultimate 360 | 62 | $274 | Folate (Nutrition) |
| GLP Optimization | 46 | $224 | Folate (Nutrition) |
SiPhox measures serum folate, not RBC folate, so treat a single low-normal result as a prompt to recheck rather than a verdict. Because serum folate responds to your last meal, collect before eating if you can and keep that the same each time; the EasyDraw instructions we read do not set a fasting rule. Both panels also include B12, ferritin and iron. There is no included doctor review. See the GLP-1 blood test page and our SiPhox review.
Ultimate 360
Everything on the four core panels plus iron studies, B12 and folate, GGT and PSA.
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GLP Optimization
Built for people on GLP-1 medication: metabolic, liver, kidney, nutrient and iron markers.
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Frequently asked questions
What is a normal folate level?
2.7 to 17.0 ng/mL (6.12 to 38.52 nmol/L) for serum folate, according to MedlinePlus. The NIH says above 3 ng/mL indicates adequate folate.
Do I need to fast for a folate blood test?
Yes. MedlinePlus says not to eat or drink for 6 hours beforehand, because recent intake raises serum folate.
What is the difference between serum and RBC folate?
Serum folate reflects recent intake; RBC folate is a longer-term measure. The NIH uses above 3 ng/mL (serum) and above 140 ng/mL (RBC) as adequate.
What causes low folate?
A diet low in folate, malabsorption such as celiac disease, pregnancy, alcohol use disorder, dialysis and some medicines, including some seizure drugs (MedlinePlus; Cleveland Clinic).