On this page
- What are the symptoms of folate deficiency?
- Why folate deficiency is easy to confuse with other problems
- What causes folate deficiency?
- Which medicines can lower folate?
- How is folate deficiency diagnosed?
- How is folate deficiency treated?
- Folate deficiency and pregnancy
- When to see a clinician
- Frequently asked questions
- Sources
- Folate deficiency can cause megaloblastic anemia, with fatigue, weakness, headache, palpitations, and shortness of breath.
- The symptoms overlap with vitamin B12 deficiency, iron deficiency, thyroid disease, and other conditions, so symptoms alone cannot confirm it.
- Common causes include low intake, alcohol use disorder, malabsorption, gastric surgery, pregnancy, and certain medicines.
- Diagnosis uses blood tests read alongside a complete blood count and vitamin B12, not a symptom checklist.
- Folic acid treats folate-deficiency anemia, but vitamin B12 deficiency should be assessed before treating unexplained anemia.
Folic acid deficiency (more precisely, folate deficiency) mainly shows up as megaloblastic anemia, which can cause fatigue, weakness, difficulty concentrating, irritability, headache, palpitations, and shortness of breath.1 Other signs include a sore or ulcerated tongue and mouth, digestive symptoms, and pigment changes in the skin, hair, or nails.1 This page covers the symptoms, why they are easy to mistake for other conditions, who is at risk, and how deficiency is tested and treated.
What are the symptoms of folate deficiency?
Folate is needed to make DNA and to support rapidly dividing cells, including red blood cells.1 When folate runs low, red blood cell production is disrupted, which can lead to megaloblastic anemia (large, immature red blood cells).1
| Symptom group | What people may notice |
|---|---|
| Anemia symptoms | Fatigue, weakness, shortness of breath, palpitations, headache 1 |
| Thinking and mood | Difficulty concentrating, irritability 1 |
| Mouth | Sore or ulcerated tongue and mouth 1 |
| Digestive | Gastrointestinal symptoms 1 |
| Skin, hair, and nails | Pigment changes 1 |
| Lab finding | High homocysteine 1 |
Why folate deficiency is easy to confuse with other problems
Folate and vitamin B12 are both needed to make healthy red blood cells, and a shortage of either can cause anemia.3 Folate is also not the same nutrient as iron, even though prenatal and anemia products often combine them.31
The most important overlap is with vitamin B12 deficiency. Large amounts of folate can correct the anemia of B12 deficiency without fixing the underlying nerve damage.41 That is why clinicians check B12 whenever megaloblastic anemia or nerve symptoms are possible, rather than treating with folic acid alone.1 Our page on how folic acid and vitamin B12 work together explains this in more detail.
Signs that point toward a broader workup
Numbness, tingling, balance problems, or changes in memory and thinking alongside anemia are reasons to ask about B12 deficiency, not just folate.24
What causes folate deficiency?
Isolated folate deficiency is uncommon in the U.S., where many enriched grain products are fortified with folic acid, and it often occurs together with other nutrient deficiencies.1 Most cases trace back to one or more of these causes.
| Cause or risk context | Why it matters |
|---|---|
| Low dietary intake | Not enough folate from food or fortified products 1 |
| Alcohol use disorder | Reduces absorption and liver uptake, speeds breakdown, and increases urinary loss 1 |
| Malabsorption, celiac disease, inflammatory bowel disease | Less folate absorbed from the gut 1 |
| Bariatric or other gastric surgery | Can impair absorption 1 |
| Pregnancy | Increased needs (RDA rises to 600 mcg DFE per day) 1 |
| Certain medicines | Some drugs impair folate absorption or metabolism 1 |
How alcohol lowers folate
Alcohol affects folate at several steps. It can reduce absorption in the intestine and uptake by the liver, accelerate folate breakdown, and increase how much is lost in urine.1 Heavy drinking also commonly comes with an inadequate diet, which compounds the problem.1
Which medicines can lower folate?
Several medicines interfere with folate absorption or metabolism. Do not stop or change any of these on your own; the right response depends on the drug, dose, and condition.
| Medicine or class | Effect on folate |
|---|---|
| Methotrexate | Blocks folate pathways; prescribed folic acid often reduces side effects in low-dose regimens 56 |
| Phenytoin, carbamazepine, valproate | Can lower folate status; supplements can also affect drug levels or seizure control 1 |
| Sulfasalazine | Can inhibit intestinal folate absorption 1 |
| Trimethoprim and other folate antagonists | Can interfere with folate metabolism 7 |
If you take methotrexate, see our guide to methotrexate and folic acid and follow your prescriber's exact schedule.6
How is folate deficiency diagnosed?
A clinician usually reads a folate test together with a complete blood count, red cell indices, a blood smear, vitamin B12, and your history of diet, alcohol use, medicines, and possible malabsorption.82 Large red blood cells (macrocytosis) should prompt testing for both folate and B12 rather than automatic folic acid treatment.2
| Test | What it shows |
|---|---|
| Serum folate | Recent intake; generally the first-line folate test 91 |
| Red blood cell folate | Longer-term status; not routinely needed when serum results and the clinical picture are clear 91 |
| Homocysteine | Can rise with folate deficiency, but also with B12 deficiency and kidney problems 91 |
Reference ranges differ by laboratory. Our folate blood test guide explains what normal, low, and high results mean.1
How is folate deficiency treated?
Folic acid treats folate-deficiency megaloblastic anemia when the diagnosis is correct.104 Treatment also has to address the cause, such as malabsorption, poor diet, alcohol exposure, or a medicine that interferes with folate.10
The dose and duration depend on the diagnosis and are set by the treating clinician.10 Treatment doses are different from everyday prevention doses, so do not use a treatment dose you have read about online.106
Prevention is a different question
For healthy adults, the recommended intake is 400 mcg DFE per day, and many people meet it through food, especially fortified foods.111 Our page on how much folic acid to take covers everyday amounts, and our list of foods high in folic acid and folate shows where it comes from in the diet.
Folate deficiency and pregnancy
Low maternal folate increases the risk of neural tube defects (NTDs), and inadequate status has also been associated with low birth weight, preterm delivery, and impaired fetal growth.1 Those associations do not mean that extra folic acid above recommended amounts prevents every adverse pregnancy outcome.1
CDC recommends 400 mcg of folic acid every day for everyone who could become pregnant, from supplements, fortified foods, or both, in addition to a varied diet.1211 USPSTF recommends a daily supplement of 400 to 800 mcg starting at least one month before conception and continuing through the first two to three months of pregnancy.13 See how much folic acid to take for pregnancy for the full guidance, including higher-risk situations.
When to see a clinician
A clinician can order the right tests, check vitamin B12 at the same time, and find the cause rather than only treating the number on a lab report.82
Frequently asked questions
What are the first signs of low folate?
Can folate deficiency cause hair loss?
How common is folate deficiency in the US?
Isolated folate deficiency is uncommon in the United States because many grain products are fortified with folic acid. When it does occur, it often appears alongside other nutrient deficiencies 1.
Should I just take folic acid if I think I am deficient?
Does alcohol cause folate deficiency?
It can. Alcohol can reduce absorption in the gut and uptake by the liver, speed up folate breakdown, and increase loss in urine. Heavy drinking also often goes with a poor diet 1.
Sources
- NIH Office of Dietary Supplements. Folate - Health Professional Fact Sheet.
- PubMed Central, NIH. Diagnosis and Treatment of Macrocytic Anemias in Adults (Nagao, 2017).
- National Heart, Lung, and Blood Institute (NHLBI). Anemia in Brief.
- PubMed Central, NIH. Excess Folic Acid and Vitamin B12 Deficiency (Miller, 2024).
- MedlinePlus, U.S. National Library of Medicine. Methotrexate: Drug Information.
- NHS Specialist Pharmacy Service. Using folic acid with methotrexate in rheumatoid arthritis.
- NHS Specialist Pharmacy Service. Managing interactions with methotrexate.
- NCBI Bookshelf, NIH. Folate Testing: Main Study Findings and Authors' Conclusions.
- PubMed, NIH. Guidelines for the Diagnosis and Treatment of Cobalamin and Folate Disorders (Devalia, 2014).
- NHS (UK National Health Service). Folic Acid: Medicine Information.
- Centers for Disease Control and Prevention (CDC). About Folic Acid.
- Centers for Disease Control and Prevention (CDC). Folic Acid: Sources and Recommended Intake.
- U.S. Preventive Services Task Force (USPSTF). Folic Acid Supplementation to Prevent Neural Tube Defects: Recommendation.
This article is for general education and is not medical advice. Doses and needs differ from person to person, so talk with your clinician or pharmacist about your situation. Read our editorial policy and medical disclaimer.
