Folic Acid (Vitamin B9)
Pronunciation: Not established from the source reviewed for this draft..
- Generic name
- folic acid
- Drug class
- Water-soluble B vitamin
- Form
- Not established from the source reviewed for this draft.
- Route
- Not established from the source reviewed for this draft.
- Legal status
- Available as an over-the-counter dietary supplement and as a prescription-strength therapeutic agent for folate-deficiency conditions; specific jurisdictional availability was not established from the source reviewed.
Availability and supply rules vary by country
Trade names by country: United States · Canada
Australia: · Full directory
What folic acid is and how it works
Folate is vitamin B9, needed for red blood cell production and healthy cell growth. Folic acid is the synthetic form used in supplements and food fortification. (1)
Folic acid is used to prevent neural tube defects when taken before and during early pregnancy, and to treat folate deficiency. It also helps manage blood homocysteine levels together with vitamins B6 and B12. Other possible uses, such as reducing cancer risk, depression, or autism-risk when taken in pregnancy, remain areas of ongoing research and are not established indications.
Mechanism of action: how folic acid works
Folic acid is the synthetic form of folate (vitamin B9), a water-soluble vitamin. Detailed mechanism-of-action wording beyond this class-level description was not established from the source reviewed for this draft. (1)
What folic acid is used for
Prevention of neural tube defects
Folic acid supplements taken before and during early pregnancy can prevent birth defects affecting the brain and spinal cord (neural tube defects). The recommended intake for people who can become pregnant is 400–800 micrograms (mcg) daily, ideally starting at least one month before conception and continuing through the first 12 weeks of pregnancy. (1)
Folate deficiency
Supplementation is used when dietary folate intake is inadequate or absorption is impaired, as determined by a healthcare provider. (1)
Homocysteine management
Folate works together with vitamins B6 and B12 to help manage blood homocysteine levels, which may relate to cardiovascular disease and stroke risk. This is an area of research and not a proven treatment indication for folic acid alone. (1)
Before taking folic acid
Do not take / not appropriate for
- Tell your healthcare provider or pharmacist before taking folic acid if you have ever had an allergic reaction to it or any of its ingredients; allergic reactions, though rare, can include skin rash, itching, difficulty breathing, and skin discoloration. Let them decide whether folic acid is appropriate for you. (all products) (1)
Tell your clinician about
- Whether you are pregnant, planning pregnancy, or breastfeeding, and any dietary or health concerns.
- Any known or suspected vitamin B12 deficiency; high-dose folic acid can correct the anemia of B12 deficiency without correcting nerve damage, allowing neurological injury to progress unnoticed.
- All prescription and over‑the‑counter medicines you take, especially anticonvulsants (carbamazepine, phenytoin, valproate), barbiturates, methotrexate, or pyrimethamine.
- Any previous allergic reaction to folic acid or other supplements.
How to take folic acid
- Take folic acid exactly as directed by your healthcare provider or the product label. For general adult health, the typical daily intake is about 400 micrograms (mcg). During pregnancy, 400–800 mcg daily is generally advised, starting at least one month before conception and through the first 12 weeks.
- Specific administration instructions (such as whether to take with or without food, or with a particular amount of water) were not established from the source reviewed for this draft; follow the instructions on your specific product label.
- Contact your healthcare provider before making any change to your folic acid use or dose, especially if you are taking other medicines that folic acid may interact with; let them advise on whether and how to adjust it.
Procedures and treatment changes
Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1)
Missed dose
The reviewed source did not include specific missed-dose guidance. Ask your pharmacist or healthcare provider for advice about a missed dose rather than making a scheduling decision on your own.
Overdose
Because excess folic acid is excreted in the urine, toxicity from typical over-supplementation is considered unlikely. However, high-dose use can mask vitamin B12 deficiency. A specific overdose-management protocol was not established from the source reviewed; if an overdose is suspected or you experience unusual symptoms, seek medical attention promptly and let the clinician assessing you advise on next steps. (1)
Side effects
Side effects are more common at high doses. Allergic reactions are rare but can be serious.
Bitter or unpleasant taste
What to notice: A lingering bitter taste in the mouth after taking the supplement.
What to do: This effect is usually mild; if it persists or bothers you, discuss it with your healthcare provider. (1)
Gastrointestinal discomfort
What to notice: Nausea, loose stools/diarrhea, stomach cramps.
What to do: If symptoms are severe or persistent, consult your healthcare provider. (1)
Nervous system effects (high doses)
What to notice: Confusion, irritability, trouble sleeping.
What to do: Contact your healthcare provider for evaluation; they can advise on next steps regarding your dose. (1)
Allergic reaction
What to notice: Skin rash, itching, difficulty breathing, skin discoloration.
What to do: Seek medical attention promptly and let the clinician assessing you advise on whether to continue or stop the supplement. (1)
Serious warnings
Allergic reaction — emergency
Symptoms: Skin rash, itching, difficulty breathing, or skin discoloration, as reported in the source reviewed. A more detailed anaphylaxis symptom checklist (e.g., facial/throat swelling) was not established from the source reviewed.
Action: Seek prompt medical attention for any of these symptoms. (1)
Vitamin B12 deficiency masking — caution
Symptoms: High-dose folic acid can correct the anemia caused by vitamin B12 deficiency without stopping the associated neurological damage. Specific symptom examples of progressing nerve damage were not established from the source reviewed.
Action: Discuss your vitamin B12 status with your healthcare provider before starting high-dose folic acid, and let your provider know about any new or unusual symptoms. (1)
Interactions
| Medicine or test | Effect | Action |
|---|---|---|
| Anticonvulsant/antiepileptic medicines (carbamazepine, phenytoin, valproate) | Folic acid may reduce the effectiveness of these medicines. | Consult your healthcare provider before combining folic acid with any of these medicines. (1) |
| Barbiturates | Folic acid may decrease the effectiveness of barbiturate medicines. | Consult your healthcare provider before combining folic acid with any barbiturate. (1) |
| Methotrexate | Folic acid may affect the intended effectiveness of methotrexate, which is a folate‑pathway antagonist used in cancer and autoimmune treatment. | If you are taking methotrexate, seek advice from the prescribing clinician before using folic acid; they will determine whether and how it should be used alongside your treatment. (1) |
| Pyrimethamine (an antimalarial/antiparasitic medicine) | Folic acid may reduce pyrimethamine’s effectiveness. | Seek medical advice before taking folic acid if you are using pyrimethamine. (1) |
Pregnancy, breastfeeding, kidney/liver function, age
Pregnancy and breastfeeding
Folic acid is recommended before conception and during early pregnancy to prevent neural tube defects (400‑800 mcg/day). Adequate folate is important for fetal development. Discuss your specific dose with a healthcare provider. Breastfeeding requirements were not detailed in the reviewed source; consult your provider. (1)
Children
No pediatric‑specific dosing was found in the reviewed source. Folic acid needs should be assessed by a paediatric healthcare professional based on age, diet, and any medical conditions.
Monitoring
Before starting
- Specific pre-treatment monitoring or laboratory-testing guidance was not established from the source reviewed for this draft.
During treatment
- Be aware of signs of allergic reaction.
- Specific laboratory-monitoring tests and intervals were not established from the source reviewed for this draft; follow your clinician's guidance.
Storage
Storage instructions were not established from the source reviewed for this draft. Always follow the specific directions on your product's packaging and patient information leaflet.
Professional information
Clinician‑facing context only. This monograph is based solely on the Mayo Clinic drugs and supplements monograph for folate (folic acid); no prescription product label was reviewed. Use current local prescribing information and clinical guidelines for deficiency management.
General
Indication: Adult supplementation (general health)
Dose summary: Typically 400 mcg daily.
Renal context: Renal impairment dosing was not reviewed in the source. (1)
General
Indication: Pregnancy / neural tube defect prevention
Dose summary: 400–800 mcg daily, starting at least 1 month before conception and through the first 12 weeks of pregnancy.
Renal context: Renal impairment dosing was not reviewed in the source. (1)
Hepatic guidance
Hepatic impairment dosing was not reviewed in this source; consult product‑specific information.
Overdose note
Excess folic acid is largely eliminated via urine, and toxicity from typical over-supplementation is considered unlikely. High-dose use can mask vitamin B12 deficiency. No specific overdose-management protocol was established from the source reviewed. (1)
Frequently asked questions
What is folic acid used for?
Folic acid is used to prevent birth defects of the brain and spinal cord (neural tube defects) when taken before and during early pregnancy. It is also used to treat folate deficiency and, together with vitamins B6 and B12, to help control homocysteine levels. (1)
How much folic acid should I take if I am pregnant or planning to become pregnant?
Current guidance suggests 400–800 micrograms (mcg) daily, ideally starting at least one month before conception and continuing through the first 12 weeks of pregnancy. Always discuss the exact dose with your healthcare provider. (1)
Can taking folic acid hide a vitamin B12 deficiency?
Yes. High‑dose folic acid can correct the anemia caused by B12 deficiency without improving the associated nerve damage, allowing the neurological effects to progress unnoticed. For this reason, supplements that combine folic acid with 100% of the Daily Value of vitamin B12 are often recommended. Always inform your healthcare provider if you have concerns about B12 status. (1)
What is the mechanism of action of folic acid?
Folic acid is the synthetic form of folate (vitamin B9), a water-soluble vitamin. Detailed mechanism-of-action wording beyond this class-level description was not established from the source reviewed for this draft. (1)
What is the generic name of Folic Acid (Vitamin B9)?
The generic name is folic acid. (1)
What class of drug is folic acid?
Folic Acid (Vitamin B9) is classed as: Water-soluble B vitamin. (1)
References
- Folate (folic acid) drugs and supplements monographMayo Clinic · United States · accessed 2026-08-05 · source 1
- FOLIC ACID TABLET [RISING PHARMA HOLDINGS, INC.] — US prescribing information (DailyMed SPL)U.S. National Library of Medicine (DailyMed) · US · accessed 2026-08-14 · source 2
- Folic Acid — patient drug information (MedlinePlus)U.S. National Library of Medicine (MedlinePlus) · US · accessed 2026-08-14 · source 3
- folic acid — RxNorm normalized drug concept (RXCUI 4511)U.S. National Library of Medicine (RxNorm) · US · accessed 2026-08-14 · source 4
Brand names by country
Single-ingredient folic acid names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.
Priority countries
United States
- QUIOFIC1 mg/5mL · solubiomix, llc
Canada
- EURO-FOLIC