Megaloblastic anaemia
Prescribing Notes:
- Megaloblastic anaemia is usually due to vitamin B12 or folate deficiency; the specific deficiency and underlying cause must be identified. Treatment is usually only begun once a firm diagnosis is made. In emergencies, where delayed treatment may be dangerous, both folate and vitamin B12 may be required initially, until assay results are known. Folate must not be used alone in undiagnosed megaloblastic anaemia due to the risk of B12 deficiency leading to peripheral neuropathy.
History Notes
20/04/2023
East Region Formulary content agreed.
By intramuscular injection.
Anaemia without neurological involvement, 1mg 3 times a week for 2 weeks then 1mg every 3 months.
Anaemia with neurological involvement, 1mg on alternate days until no further improvement then 1mg every 2 months.
Prophylaxis, 1mg every 3 months.
Tobacco amblyopia and Leber’s optic atrophy, 1mg daily for 2 weeks then 1mg twice weekly until no further improvement, thereafter 1mg every 1-3 months.
Prescribing Notes:
- Apart from dietary deficiency all other causes of vitamin B12 deficiency are attributable to malabsorption. Vitamin B12 should be given prophylactically after total gastrectomy or total ileal resection.
- There is little place for use of low dose vitamin B12 orally. However, cyanocobalamin tablets can be used in doses of 50-150micrograms daily for vegans or patients who have proven dietary deficiency.
- Oral cyanocobalamin in larger daily doses of 1-2mg (unlicensed dose) may be effective in patients who experience hypersensitivity reactions to the injection or are unable to receive intramuscular injections.
- There is no evidence that doses larger than those recommended provide any additional benefit in cases with neurological or ocular involvement.
- For local clinical guidelines, including advice for when intra-muscular B12 is required and where dietary advice is appropriate, please see RefHelp (NHS Lothian) and the NHS Fife B12 Investigation and Management
History Notes
06/02/2025
Update to prescribing information, ERWG Jan 2025
20/04/2023
East Region Formulary content agreed.
Liquid preparations should only be used when patients cannot tolerate or use solid formulations.
Folate deficient state (e.g. pregnancy, poor nutrition, concurrent antiepileptics), 5mg daily for 4 months (until term in pregnant women); doses up to 15mg daily may be required in malabsorption states.
Folate deficient state (e.g. pregnancy, poor nutrition, concurrent antiepileptics), 5mg daily for 4 months (until term in pregnant women); doses up to 15mg daily may be required in malabsorption states.
Prescribing Notes:
- There is no need to routinely prescribe a combined iron/folic acid preparation in pregnancy.
- Folic acid has few indications for long-term therapy since most causes of folate deficiency are self-limiting or will yield to a short course of therapy.
- Where B12 and folate deficiency are identified, B12 replacement should be initiated first.
History Notes
20/04/2023
East Region Formulary content agreed.
Liquid preparations should only be used when patients cannot tolerate or use solid formulations.
5mg every 1-7 days dependent on underlying disease.
5mg every 1-7 days dependent on underlying disease.
Prescribing Notes:
- There is no need to routinely prescribe a combined iron/folic acid preparation in pregnancy.
- Folic acid has few indications for long-term therapy since most causes of folate deficiency are self-limiting or will yield to a short course of therapy.
History Notes
20/04/2023
East Region Formulary content agreed.
See prescribing notes.
400micrograms daily, to be taken before conception and until week 12 of pregnancy.
5mg daily, to be taken before conception and until week 12 of pregnancy.
Prescribing Notes:
- There is no need to routinely prescribe a combined iron/folic acid preparation in pregnancy.
- Folic acid 400micrograms daily should be recommended for all women attempting to conceive and continued until the 12th week of pregnancy to reduce the risk of a neural tube defect.
- Women at high risk (women with epilepsy, with diabetes, with coeliac disease, with a chronic haemolytic state or with a BMI >30 and those with a previous affected pregnancy) should take 5mg from pre-conception until 12 weeks.
History Notes
20/04/2023
East Region Formulary content agreed.
Prescribing Notes:
- Megaloblastic anaemia is very rare in children and is usually due to vitamin B12 or folate deficiency; the specific deficiency and underlying cause must be identified. Treatment is usually only begun once a firm diagnosis is made. Folate must not be used alone in undiagnosed megaloblastic anaemia due to the risk of B12 deficiency leading to peripheral neuropathy.
History Notes
10/06/2020
Content migrated from LJF website.
All ages, confirmed vitamin B12 deficiency, by intramuscular injection, 250microgram-1mg 3 times weekly for 2 weeks then 250microgram once weekly until blood count is normal, then 1mg every 2-3 months.
Prescribing Notes:
- Hydroxocobalamin injection solution can be given orally.
- Neonates born to vitamin B12 deficient mothers may be vitamin B12 deficient themselves and require a course until the haemoglobin is normal. If there is malabsorption e.g. total Ileal Space resection, then maintenance doses of vitamin B12 may be required.
- Dietary deficiency of vitamin B12 is rare in children unless they are on a vegan diet.
- There is little place for use of low dose vitamin B12 orally. However, cyanocobalamin tablets can be used in doses of 50-105micrograms daily for vegans or children with proven dietary deficiency.
History Notes
10/06/2020
Content migrated from LJF website.
Neonate: initially 500micrograms/kg once daily for up to 4 months.
1-11 months: initially 500micrograms/kg once daily (max. per dose 5mg) for up to 4 months, doses up to 10mg daily may be required in malabsorption states.
1-17 years: 5mg daily for 4 months (until term in pregnant women), doses up to 15mg daily may be required in malabsorption states. Ongoing treatment may be required in those with uncorrectable causes.
Neonate: initially 500micrograms/kg once daily for up to 4 months.
1-11 months: initially 500micrograms/kg once daily (max. per dose 5mg) for up to 4 months, doses up to 10mg daily may be required in malabsorption states.
1-17 years: 5mg daily for 4 months (until term in pregnant women), doses up to 15mg daily may be required in malabsorption states. Ongoing treatment may be required in those with uncorrectable causes.
Prescribing Notes:
- Treatment is given for up to 4 months. For maintenance therapy, treatment doses may be given at daily to weekly intervals.
History Notes
10/06/2020
Content migrated from LJF website.
All ages - 250micrograms/kg daily for 6 months if a correctable cause or for life if uncorrectable cause.
All ages - 250micrograms/kg daily for 6 months if a correctable cause or for life if uncorrectable cause.
Prescribing Notes:
- Folate deficient states may develop due to different factors e.g. poor nutrition or treatment with antiepileptics, and as a co-factor in metabolic disorders.
History Notes
10/06/2020
Content migrated from LJF website.
1 month-11 years, 2.5-5mg once daily.
12-17 years, 5-10mg once daily.
1 month-11 years, 2.5-5mg once daily.
12-17 years, 5-10mg once daily.
History Notes
10/06/2020
Content migrated from LJF website.
All ages, 5mg once a week 24 hours after methotrexate.
All ages, 5mg once a week 24 hours after methotrexate.
History Notes
10/06/2020
Content migrated from LJF website.