Folate deficiency (B9) ✅
🤰🌱 Folate supplementation should be offered to anyone planning pregnancy or in early pregnancy to reduce the risk of neural tube defects such as spina bifida.
Folate is also essential for DNA synthesis, red cell production and rapidly dividing tissues.
ℹ️ About
- 🍞 The UK has introduced mandatory folic acid fortification of non-wholemeal wheat flour to help reduce neural tube defects.
- 🥦 Folate is vitamin B9 and is naturally found in green vegetables, legumes, citrus fruits and fortified foods.
- 🧬 Folic acid is the synthetic form used in supplements and food fortification.
- 👶 Periconception folic acid is most important because the neural tube closes very early in pregnancy, often before pregnancy is recognised.
🧬 Aetiology / Pathophysiology
- 🧪 Folate is required for DNA synthesis, especially thymidine production.
- 🩸 Deficiency impairs nuclear maturation in red cell precursors, causing megaloblastic anaemia.
- 👅 Rapidly dividing tissues are affected first, so patients may develop glossitis, mouth ulcers and anaemia symptoms.
- 📦 Folate stores are limited and may last only a few months, so deficiency can develop relatively quickly with poor intake or increased demand.
- 🏥 Folate is absorbed mainly in the small bowel, especially the proximal jejunum.
⚠️ Causes of Folate Deficiency
- 🥗 Poor intake: Malnutrition, alcohol excess, restrictive diets, anorexia, food fads, frailty or poor social circumstances.
- 🌾 Malabsorption: Coeliac disease, tropical sprue, inflammatory bowel disease or small bowel resection.
- 🤰 Increased requirements: Pregnancy, lactation, prematurity, malignancy and chronic inflammatory states.
- 🩸 Chronic blood disorders: Haemolytic anaemia, sickle cell disease and other high-turnover marrow states.
- 🧬 Metabolic disorders: Homocystinuria and rare inherited folate pathway disorders.
- 🧫 Dialysis: Haemodialysis or peritoneal dialysis may increase folate loss.
- 💊 Drug-induced: Methotrexate, trimethoprim, phenytoin, some anticonvulsants, sulfasalazine, nitrofurantoin and alcohol.
- 🧬 Rare genetic causes: Folate transporter deficiency, including SLC46A1-related disease.
🩺 Clinical Features
- 😴 Fatigue, lethargy, weakness or reduced exercise tolerance.
- 💓 Palpitations, breathlessness or dizziness from anaemia.
- 👅 Glossitis, angular cheilitis or mouth ulcers.
- 🩸 Macrocytic anaemia, often with raised MCV.
- 🧠 Mood change, irritability or depression may occur.
- ⚠️ Neurological symptoms such as numbness, paraesthesia or gait disturbance should raise concern for vitamin B12 deficiency, not simple folate deficiency.
🔍 Differential Diagnoses
- 🧠 Vitamin B12 deficiency - especially if neurological symptoms are present.
- 🍷 Alcohol excess.
- 🧫 Liver disease.
- 🦋 Hypothyroidism.
- 🤰 Pregnancy-related macrocytosis.
- 🩸 Reticulocytosis after bleeding or haemolysis.
- 🧬 Bone marrow disorders, including myelodysplasia, aplastic anaemia and pure red cell aplasia.
🔎 Investigations
- 🩸 FBC: Macrocytic anaemia with raised MCV, often >96 fL.
- 🔬 Blood film: Megaloblastic changes with macro-ovalocytes and hypersegmented neutrophils.
- 🌱 Serum folate: Low levels support deficiency, but recent folate intake can falsely reassure.
- 📦 Red cell folate: May better reflect longer-term folate stores, depending on local laboratory practice.
- 🧠 Vitamin B12: Check before or alongside folate replacement, because folic acid can mask haematological features of B12 deficiency.
- 🧪 Consider: LFTs, TFTs, coeliac screen, haematinics and reticulocyte count depending on the clinical picture.
💊 Management
- 🌱 Treat confirmed folate deficiency with folic acid 5 mg once daily.
- ⏳ Most adults require treatment for around 4 months, or longer if the underlying cause persists.
- 🤰 In pregnancy, continue treatment according to indication and local guidance; higher-dose folic acid may be needed in high-risk groups.
- 🌾 Treat reversible causes such as coeliac disease, poor diet, alcohol excess or drug-related deficiency.
- 🥗 Give dietary advice: leafy greens, pulses, beans, peas, citrus fruit and fortified foods.
- 🧠 If vitamin B12 deficiency is present or suspected, replace B12 first or at the same time to reduce the risk of neurological deterioration.
🤰 Pregnancy Supplementation
- ✅ Standard prevention: folic acid is advised before conception and during early pregnancy.
- ⚠️ Higher-dose folic acid may be required for high-risk patients, such as previous neural tube defect, certain anti-epileptic medicines, diabetes, malabsorption or high BMI.
- 🕒 The key window is before conception and the first 12 weeks of pregnancy, because neural tube development occurs very early.
🧠 Exam Pearls
- 💡 Folate deficiency causes megaloblastic macrocytic anaemia.
- 💡 Neurological signs point more strongly towards B12 deficiency.
- 💡 Never treat macrocytosis with folate alone without considering B12.
- 💡 Pregnancy increases folate requirement because of rapid fetal and placental growth.
📚 References
📝 Revisions
- ✅ Added pregnancy prevention advice, B12 safety warning and emoji-enhanced teaching points.
- ✅ Clarified that neurological symptoms should prompt concern for B12 deficiency.
- ✅ Added UK flour fortification context.
