Folate (Folic) acid (B9) 💊
⚠️ Safety Tip:
Always check Vitamin B12 levels first.
❌ Never give folic acid alone in suspected or confirmed pernicious anaemia, as it can precipitate subacute combined degeneration of the spinal cord.
📖 About
Always check the BNF link here.
- 🧬 Essential vitamin for synthesis of nitrogenous bases in DNA and RNA.
- 🔄 Needed for red cell production and rapid cell turnover (pregnancy, haemolysis).
⚡ Mechanism of Action
- Coenzyme in one-carbon transfer reactions in purine/pyrimidine synthesis.
- Supports erythropoiesis and prevents megaloblastic changes.
🩺 Indications
- 👩🍼 Pre-pregnancy: reduces risk of neural tube defects.
- 🤰 First trimester: prevents neural tube defects; higher dose for high-risk women (epilepsy meds, diabetes, obesity, FHx NTDs).
- 🍽️ Folate deficiency – dietary, malabsorption, alcoholism, high metabolic states.
- 🩸 Chronic haemolytic anaemias (e.g. sickle cell, thalassaemia).
- 📉 Drug-induced folate deficiency (methotrexate, phenytoin, trimethoprim).
💊 Dose
- 📉 Folate deficiency: 5 mg PO OD for 4 months (up to 15 mg daily in severe deficiency).
- 🤰 Pregnancy: 5 mg PO OD from pre-conception until week 12 of pregnancy.
- 🧬 Chronic haemolysis: 5 mg PO daily (1–7x per week depending on severity).
- 📌 If B12 deficiency co-exists → replace both simultaneously.
⚠️ Interactions
- See BNF – interactions with anticonvulsants (phenytoin), antifolates (methotrexate, trimethoprim).
⚠️ Cautions
- ❌ Do not give in undiagnosed macrocytic anaemia until B12 deficiency excluded.
- Risk of masking B12 deficiency → can allow neurological damage to progress.
🚫 Contraindications
- Untreated or unrecognised Vitamin B12 deficiency (pernicious anaemia, dietary deficiency, malabsorption).
- Unexplained megaloblastic anaemia without full workup.
💥 Side Effects
- 🧠 Subacute combined degeneration of the spinal cord (if B12 deficiency not corrected at same time).
- 🤢 GI upset: dyspepsia, nausea, bloating.
- 🌡️ Rare: allergic reactions, pruritus, erythema.
- 🩸 May rarely precipitate seizures in predisposed patients on anticonvulsants.
📑 References
- BNF: Folic Acid
- UK Chief Medical Officer: Neural Tube Defect Prevention Guidance
