Macrocytic; peripheral neuropathy, ↓proprioception, glossitis, hypersegmented neutrophils; alcoholism
Confirm: B12 + folate levels; ↑methylmalonic acid + ↑homocysteine (most accurate)
Treat: Cyanocobalamin 1000 µg IM daily×1 wk → weekly×4 → monthly (lifelong if pernicious)
Order set
- B12, folate
- MMA/homocysteine
- FBC, film
- Intrinsic factor/parietal antibodies
Criteria
AdmitSevere anaemia or neuro compromise
TransfuseRarely; only if severe symptomatic
DischargeReplacement started, cause identified, neuro monitored
Never
- Give folate alone — corrects anemia but NOT neuro damage; replace B12 first
Clinical detail — differentials, red flags, pitfalls, disposition
Red flags
- Subacute combined degeneration
- Pancytopenia
Differentials
- Folate deficiency
- Diabetic neuropathy
- MDS
Common mistakes
- Folate before B12 (worsens neuro)
- Missing pernicious anaemia
Disposition & follow-up
IM B12 replacement; treat cause; monitor response.
Discharge package
MedicationsMaintenance B12 (IM/oral); folate if co-deficient
Follow-upRecheck response; lifelong if pernicious
Warning symptomsWorsening neuropathy, imbalance
💊 Treatment detail — doses & preparation
Cyanocobalamin (B12)vitamin
Dose1000 mcg IM daily ×1 wk → weekly ×4 → monthly lifelong (pernicious/neuro)
Preparation1000 mcg/mL ampoule IM
MonitorReticulocytes day 5–7, K⁺ (can fall early); never give folate alone first
Folate cautionsafety
DoseNever give folic acid alone before B12 corrected — worsens neurology
Preparation—
MonitorReticulocyte rise day 5–7 confirms response
📖 BSH Cobalamin & FolateReviewed July 2026