Folate Forms — Clinical Comparison
| Form | Active? | Routes | Key Use | India Availability |
|---|
| Folic Acid | Prodrug (needs conversion) | Oral, IM, IV | Pregnancy prophylaxis, anaemia, deficiency | Universal; tablets 0.4 mg, 1 mg, 5 mg |
| Folinic Acid (Leucovorin / Calcium Folinate) | ✅ Active (bypasses DHFR) | Oral, IM, IV | Methotrexate rescue, DHFR-inhibitor rescue | Available (hospitals); 15 mg, 50 mg inj |
| L-Methylfolate (5-MTHF) | ✅ Active (final active form) | Oral only | MTHFR mutation, refractory deficiency, depression adjunct | Available (limited specialty brands) |
| Folinic Acid (Levoleucovorin) | ✅ Active L-isomer | IV | High-dose MTX rescue (oncology) | Oncology centres only |
Folic Acid in Pregnancy — India Guidelines
Standard dose: 400–500 mcg (0.4–0.5 mg) daily, started at least 1 month before conception and continued through 12 weeks of gestation — reduces neural tube defect (NTD) risk by 70%. India's NHM and FOGSI recommend 500 mcg/day throughout pregnancy due to high prevalence of folate deficiency. Most antenatal iron-folic acid (IFA) tablets contain 500 mcg folic acid.
High-risk dose (5 mg/day): Women with previous NTD-affected pregnancy, on antiepileptic drugs (phenytoin, carbamazepine, valproate), pre-existing diabetes, obesity (BMI >30), coeliac disease, malabsorption, thalassaemia, or on folate antagonists. Start 3 months before conception and continue through first trimester.
Folic Acid vs Folinic Acid — When Each Is Needed
Folic acid is a synthetic oxidised form that must be converted to active tetrahydrofolate (THF) via dihydrofolate reductase (DHFR). When DHFR is inhibited — by methotrexate, trimethoprim, pyrimethamine, or trimethoprim-sulfamethoxazole — folic acid cannot be converted and is ineffective. In these situations, folinic acid (leucovorin) must be used as it bypasses DHFR entirely. Critical distinction: do not use folic acid instead of folinic acid for methotrexate rescue — it will not work.
MTHFR Mutations and L-Methylfolate
The MTHFR C677T and A1298C polymorphisms — common in Indian populations — reduce the enzyme that converts folic acid to active L-methylfolate (5-MTHF). Women with homozygous MTHFR mutations may have suboptimal folic acid conversion. L-methylfolate (5-MTHF) bypasses this conversion and may be preferred in: MTHFR mutation carriers, recurrent pregnancy loss, unexplained infertility, and patients with depression/psychiatric conditions (folate-dependent serotonin synthesis). However, routine MTHFR testing before folic acid supplementation is not currently recommended by major guidelines — most individuals with MTHFR variants respond adequately to standard folic acid doses.
Normal Folate Levels
Serum folate: 3–17 ng/mL (normal); <3 ng/mL (deficient). Red cell folate (better indicator of tissue stores): 165–600 ng/mL; <140 ng/mL indicates deficiency. Red cell folate is the preferred test as it reflects long-term folate status (not affected by recent dietary intake). In pregnancy, target serum folate >5 ng/mL for adequate NTD protection.
Frequently Asked Questions
What is the folic acid dose for pregnancy in India?
Standard dose: 400–500 mcg (0.5 mg) daily, started at least 1 month before conception and continued through 12 weeks (first trimester). FOGSI and NHM India recommend 500 mcg throughout pregnancy. High-risk women (prior NTD baby, antiepileptics, diabetes, obesity, malabsorption): 5 mg/day started 3 months before conception through first trimester, then standard dose for rest of pregnancy. Government IFA tablets contain 500 mcg folic acid + 100 mg elemental iron.
What is the dose of folic acid for megaloblastic anaemia?
Folic acid 5 mg once daily orally for 4 months (or until complete haematological recovery). Always rule out or concurrently treat B12 deficiency — giving folic acid alone in B12 deficiency corrects the blood count but allows progressive neurological damage (subacute combined degeneration of spinal cord) to continue silently. Check serum B12 before or simultaneously starting treatment. If B12 deficiency confirmed: treat both B12 and folate together.
What is folinic acid (leucovorin) and when is it used?
Folinic acid (leucovorin, calcium folinate) is the reduced active form of folate that bypasses dihydrofolate reductase (DHFR). It is used: (1) Methotrexate rescue — 15 mg every 6 hours starting 24 hours after MTX, continued until MTX levels are safe; (2) When folic acid cannot work because DHFR is blocked (methotrexate, trimethoprim, pyrimethamine therapy); (3) Combined with 5-fluorouracil (5-FU) to enhance its anti-tumour effect. Do NOT substitute folic acid for folinic acid in methotrexate rescue — folic acid will not work and toxicity will not be prevented.
Why does folic acid supplementation during methotrexate therapy not require folinic acid?
When methotrexate is used at LOW doses for rheumatoid arthritis, psoriasis, or inflammatory bowel disease (7.5–25 mg/week), folic acid 1–5 mg/day (on non-MTX days) can partially restore folate without fully antagonising the anti-inflammatory effect. This is because DHFR inhibition is incomplete at these doses. Folinic acid (leucovorin) is reserved for HIGH-DOSE MTX chemotherapy rescue — where full DHFR inhibition occurs and folic acid is ineffective. In rheumatology practice: folic acid 5 mg/week reduces MTX side effects without compromising efficacy.
What is the folic acid dose for haemolytic anaemia?
Patients with haemolytic anaemia (sickle cell disease, thalassaemia, hereditary spherocytosis, G6PD deficiency with chronic haemolysis) have increased folate requirements due to high red cell turnover. Folic acid 5 mg/day orally is recommended for all patients with chronic haemolysis. Sickle cell disease: folic acid 1–5 mg/day throughout life. Thalassaemia major (on regular transfusions): folate supplementation is often included in management. Pregnancy + haemolytic anaemia: higher dose (5 mg/day) mandatory.
What drugs cause folate deficiency?
Drugs causing folate deficiency or depletion: Methotrexate (direct DHFR inhibitor); Trimethoprim / Co-trimoxazole (weak DHFR inhibitor — clinically significant in prolonged use); Pyrimethamine (for malaria/toxoplasmosis); Antiepileptics — phenytoin, carbamazepine, valproate (impair folate absorption/metabolism); Oral contraceptive pills (mild depletion); Sulfasalazine (impairs folate absorption); Cholestyramine; Alcohol (impairs absorption and increases excretion). Screen folate status in patients on chronic therapy with any of these drugs.
What is L-methylfolate (5-MTHF) and is it better than folic acid?
L-methylfolate (5-MTHF) is the final active form of folate in the body — the form that enters cells and the brain directly. It does not require MTHFR enzyme conversion. It may be preferred in: MTHFR mutation carriers (common in India), depression (folate-dependent serotonin synthesis), recurrent pregnancy loss, and refractory folate deficiency. However, standard folic acid works adequately for most people, including most MTHFR heterozygotes. L-methylfolate is significantly more expensive than folic acid. Routine testing for MTHFR mutations before prescribing folic acid is not recommended by major guidelines.
Is folic acid safe throughout pregnancy?
Yes — folic acid is safe throughout pregnancy at standard doses (0.4–5 mg/day). The critical window for NTD prevention is periconceptional (1 month before to 12 weeks after conception) as neural tube closure occurs at 28 days post-conception — often before pregnancy is confirmed. Continuing supplementation beyond 12 weeks reduces maternal anaemia, preterm birth risk, and supports placental development. No evidence of harm from doses up to 5 mg/day in pregnancy. Upper tolerable intake level: 1000 mcg (1 mg) for dietary folate equivalents — therapeutic doses above this are considered safe under medical supervision.