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Vitamin B group (folate) Pregnancy: Essential in early pregnancy (NTD prevention). Safe and recommended.

Folic Acid

Brand names: Folic Acid, Lexpec

Adult dose

Dose: Folate deficiency anaemia: 5 mg once daily for 4 months; Prevention in pregnancy: 400 micrograms daily; High risk (previous NTD): 5 mg daily
Route: Oral
Frequency: Once daily
Max: 15 mg/day in some haematological conditions
Treatment of megaloblastic anaemia: 5 mg OD for 4 months (or longer if underlying cause not corrected). Prevention of neural tube defects: 400 micrograms/day at least 1 month before conception and for first 12 weeks. High risk: 5 mg/day.

Paediatric dose

Route: Oral
Frequency: Once daily
Max: 5 mg/day
Folate deficiency: 1–12 months: 0.5 mg OD; 1–17 years: 5 mg OD for 4 months. Prevention in haemolytic anaemia: 2.5–5 mg every 1–7 days depending on rate of haemolysis.

Dose adjustments

Renal

No dose adjustment required.

Hepatic

No dose adjustment required.

Clinical pearls

  • ALWAYS exclude B12 deficiency before starting folic acid alone — can precipitate SCD of cord
  • Women with diabetes, on antiepileptics, or with previous NTD should take 5 mg preconceptually
  • Haemolytic anaemias (sickle cell, thalassaemia) require regular folate supplementation
  • Folinic acid (leucovorin) used for methotrexate rescue — NOT folic acid

Contraindications

  • Untreated pernicious anaemia or Vitamin B12 deficiency (treat B12 simultaneously to avoid precipitating subacute combined degeneration of cord)

Side effects

  • Nausea (high doses)
  • Hypersensitivity reactions (rare)

Interactions

  • Methotrexate — antagonised by folic acid (give rescue folinic acid, not folic acid, after methotrexate)
  • Antiepileptics (phenytoin, carbamazepine, valproate) — reduced folic acid levels; folic acid 5 mg/day recommended

Monitoring

  • FBC
  • Serum folate
  • Serum B12 (before and during treatment)

Reference: BNFc; BNF; BNFc; NICE PH11 Folic Acid; RCOG Green-Top. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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