Also Known As
Folic Acid Test, Vitamin B9 Blood Test, Serum Folate Test
What Is a Folate Blood Test?
A folate RBC blood test measures the level of folate (vitamin B9) stored inside your red blood cells — giving a more accurate picture of your long-term folate status than a standard serum folate test. Folate is an essential B vitamin your body cannot produce on its own — it must come from food or supplements. It plays a critical role in DNA synthesis, red blood cell production, cell division, and fetal neural tube development.
Folate deficiency is one of the most common nutritional deficiencies in the United States, and it often goes undetected because its symptoms — fatigue, weakness, and brain fog — overlap with many other conditions. According to the CDC, adequate folate intake is essential for everyone, but especially for women of childbearing age and pregnant women, where deficiency dramatically increases the risk of serious birth defects.
What Does Folate Do in the Body?
Folate (the natural form found in food) and folic acid (the synthetic form in supplements and fortified foods) perform the same essential functions:
- DNA synthesis and repair — folate is required for building and repairing DNA in every cell
- Red blood cell production — without adequate folate, red blood cells become abnormally large and dysfunctional, causing megaloblastic anemia
- Cell division — rapidly dividing cells (bone marrow, fetal tissue) are especially dependent on folate
- Homocysteine metabolism — folate, along with B12 and B6, helps convert homocysteine into methionine, keeping cardiovascular risk low
- Fetal neural tube development — folate in the first weeks of pregnancy prevents neural tube defects like spina bifida and anencephaly
- Brain and mood health — folate supports neurotransmitter synthesis and is linked to depression risk when deficient
Folate Normal Reference Ranges
| Result | RBC Folate Level (ng/mL) | Interpretation |
|---|---|---|
| Deficient | Less than 140 | Folate deficiency, further evaluation needed |
| Borderline Low | 140–160 | May indicate early deficiency |
| Normal | 160–640 | Adequate long-term folate status |
| High | Greater than 640 | Often from supplementation |
Reference ranges may vary slightly by laboratory. Serum folate reflects recent dietary intake; RBC folate better reflects long-term stores.
What Does Low Folate Mean?
Low serum folate indicates inadequate folate status, which can result from:
- Poor diet — low intake of leafy greens, legumes, fortified grains, and citrus
- Malabsorption — celiac disease, Crohn’s disease, and other GI disorders impair folate absorption
- Alcoholism — alcohol interferes with folate absorption and increases urinary excretion
- Certain medications — methotrexate, metformin, sulfasalazine, and some anticonvulsants deplete folate
- Pregnancy — increased demand outpaces intake without supplementation
- MTHFR gene mutation — reduces the body’s ability to convert folate into its active form
Symptoms of folate deficiency include:
- Fatigue and weakness
- Mouth sores or a sore, red tongue
- Headaches
- Irritability, depression, or brain fog
- Pale skin
- Shortness of breath
- Diarrhea
- Heart palpitations or irregular heartbeat
If left untreated, folate deficiency can lead to:
- Megaloblastic anemia (large, dysfunctional red blood cells)
- Elevated homocysteine and increased cardiovascular risk
- Neural tube defects in pregnancy
- Cognitive decline and increased depression risk
Who Should Get a Folate Test?
- Women who are pregnant or planning to become pregnant
- Anyone experiencing unexplained fatigue, weakness, or brain fog
- People with a poor diet or restricted eating patterns
- Vegans and vegetarians — plant-based diets can be low in bioavailable folate
- Anyone with celiac disease, Crohn’s disease, or other GI disorders
- People who drink alcohol regularly
- Anyone taking methotrexate, metformin, or anticonvulsants long-term
- Anyone with known or suspected MTHFR gene mutation
- People with elevated homocysteine — folate deficiency is a primary cause
- Anyone recently diagnosed with anemia
Test Preparation
Fasting required: No fasting required for the RBC folate test..
Supplements: If you take folic acid supplements, note this when reviewing your results. High-dose supplementation will raise serum folate and may not reflect true tissue stores. For a more comprehensive picture of long-term folate status, consider ordering the RBC Folate test alongside this test.
How Much Does a Folate Test Cost?
| Where You Get Tested | Typical Cost | Notes |
|---|---|---|
| Personalabs (Quest) | $44 | Physician order included |
| Doctor’s office visit + lab | $150–$300+ | Office copay + lab fees |
| Hospital outpatient lab | $200–$500+ | Facility fees apply |
HSA and FSA eligible. Folate testing qualifies as a reimbursable medical expense.
How to Order Your Folate Test
Step 1: Order online — your physician-approved lab order is ready within 2–4 hours. Step 2: Find a lab near you using our Lab Locator. Step 3: Walk in for your blood draw. Step 4: Get results in your secure Personalabs account within 24–48 hours.
Frequently Asked Questions
What is the difference between folate and folic acid?
Folate is the naturally occurring form of vitamin B9 found in foods like leafy greens, legumes, and citrus fruits. Folic acid is the synthetic form used in dietary supplements and to fortify foods like bread and cereals. Both forms are converted by the body into the active form of folate (5-methyltetrahydrofolate or 5-MTHF). People with the MTHFR gene mutation may have difficulty converting folic acid efficiently and often benefit from methylated folate supplements instead.
What is the difference between serum folate and RBC folate?
Serum folate reflects your recent dietary intake — it rises quickly after eating folate-rich foods and drops within days of poor intake. RBC folate reflects your long-term folate stores over the past 2–3 months, similar to how A1c reflects long-term blood sugar. For a complete picture of folate status, testing both together is ideal. If you’re monitoring supplementation or evaluating chronic deficiency, RBC folate is generally the more informative marker.
Can folate deficiency cause depression?
Yes — low folate is consistently associated with depression and poor response to antidepressant medications. Folate is required for the synthesis of serotonin, dopamine, and norepinephrine — the neurotransmitters that regulate mood. Some research suggests that supplementing with methylfolate (the active form of folate) can improve antidepressant response in people with low folate levels, particularly those with the MTHFR mutation.
Should I test folate and B12 together?
Yes — folate and B12 work together closely, and deficiency in one can mask deficiency in the other. High folate can normalize red blood cell appearance even when B12 is dangerously low, hiding serious neurological damage. This is why the CDC recommends testing both together whenever folate deficiency is suspected. Personalabs offers a combined Vitamin B12 and Folate test for this reason.
How does folate relate to homocysteine?
Folate, B12, and B6 are the three key vitamins that break down homocysteine in the blood. When folate is deficient, homocysteine accumulates — raising cardiovascular risk and contributing to cognitive decline. If your homocysteine is elevated, testing folate and B12 together is one of the first steps in identifying the cause.
Is folate testing important during pregnancy?
Absolutely. Folate is critical in the first 28 days of pregnancy — often before a woman even knows she’s pregnant — for preventing neural tube defects like spina bifida. The CDC recommends 400 mcg of folic acid daily for all women of childbearing age. Testing folate levels before or early in pregnancy confirms whether intake and absorption are adequate and whether supplementation is working.
Related: 10 Natural Food Sources of Folate & Folic Acid for Pregnant Women
