This handout is for vitamin b12 & folate deficiency anaemia (megaloblastic; pernicious anaemia + scd). Your care team identified this based on: macrocytosis mcv >100 fl on cbc (bsh devalia 2014 pmid 24942828).
Other reasons your team may use this plan: low / borderline serum b12 (<148 pmol/l definite; 148–221 borderline) (stabler nejm 2013 pmid 23301732); low serum / red-cell folate (bsh devalia 2014 pmid 24942828); fatigue / pallor / glossitis / anaemia symptoms.
Take these medications exactly as prescribed. Do not stop or change a dose without talking to your provider.
| Medication | Starting dose | How | When | What it does |
|---|---|---|---|---|
| hydroxocobalamin | 1 mg | IM | alternate days for 1–2 weeks (until no further neuro improvement), then 1 mg every 2–3 months | BSH Devalia 2014 (PMID 24942828) — parenteral loading then lifelong maintenance for pernicious anaemia / irreversible malabsorption; preferred when neurologic involvement present |
| cyanocobalamin | 1000–2000 mcg | PO | once daily | Cochrane Wang 2018 (PMID 29543316) — high-dose oral via passive absorption non-inferior to IM for short-term haematologic + neurologic response in many causes; also IM 1 mg form for parenteral course |
| folic acid | 1–5 mg | PO | once daily for ~4 months (lifelong if chronic haemolysis / malabsorption) | BSH Devalia 2014 (PMID 24942828) — folate 1–5 mg/day; MRC Vitamin Study (PMID 1677062) periconceptional 400 mcg (4–5 mg if prior NTD). NEVER folate-alone if B12 unmeasured (SCD risk) |
| leucovorin (folinic acid) | per indication | PO/IV | per protocol | Bypasses DHFR block — used when deficiency is driven by antifolate (methotrexate / trimethoprim / pyrimethamine) rather than dietary/absorptive folate lack |
| methylcobalamin | 500–1000 mcg | PO | once daily | Active cobalamin form; adjunct/alternative oral option (incl. N2O functional deficiency where methylation cycle is blocked) — evidence base weaker than hydroxocobalamin/cyanocobalamin |
| discontinue / deprescribe offending agent + dietary correction + treat underlying | — | — | — | Stop N2O; deprescribe-or-monitor metformin/PPI (Aroda DPPOS PMID 26900641; de Jager HOME PMID 20488910); B12-fortified diet/supplements for vegans; lifelong supplementation post-bariatric/ileal resection; route Crohn to gi.crohns.core.v1 |
| packed red blood cell transfusion | — | — | — | Rarely needed; reserved for life-threatening symptomatic anaemia — transfuse cautiously (slow, small volume) given high-output state and risk of fluid overload (BSH Devalia 2014 PMID 24942828) |
Plan: B12 / folate repletion (route- and aetiology-driven)
Contact your care team if any of the following happen:
Call 911 or go to the nearest emergency room right away if you have:
Pernicious anaemia: lifelong B12 + endoscopic gastric surveillance per local pathway (gastric adenocarcinoma/carcinoid risk, ~7× RR, PMID 23216458); annual FBC + thyroid (autoimmune association — panel.thyroid). Drug-induced: periodic B12 on continued metformin/PPI (Aroda DPPOS PMID 26900641). Pregnancy: periconceptional folate 400 mcg standard, 4–5 mg if prior NTD/high-risk, continue through 12 wk; B12 in vegans/post-bariatric; infants of B12-deficient mothers screened. Geriatric: re-screen cognition if dementia-mimic. Bariatric/ileal resection: lifelong supplementation + monitoring (BSH Devalia 2014 PMID 24942828; MRC Vitamin Study PMID 1677062)
Guideline: BSH/BCSH Guidelines for the diagnosis & treatment of cobalamin & folate disorders (Devalia, BJH 2014) + Stabler NEJM 2013 clinical practice review + Cochrane oral-vs-IM B12 (Wang 2018) + ACOG/MRC periconceptional folate + N2O-myeloneuropathy literature