Low Vitamin B12 (deficiency)

Quick Overview

  • Normal B12: ≥180 ng/L → No further action if asymptomatic
  • Borderline B12: 145–180 ng/L → Check IFAB if concern or mild symptoms
  • Low B12 (<145 ng/L): Always treat - do not delay if symptomatic
  • Neurological symptoms? → Start IM treatment immediately, even before IFAB

If B12 is <145 ng/L and NO neurological symptoms

  • Start treatment immediately - do not wait for IFAB
  • IM Hydroxocobalamin 1 mg on alternate days, 3 times per week for 2 weeks
  • Then:
    • If dietary cause (e.g. vegan): switch to daily OTC oral B12 (50-150 mcg)
    • If IFAB positive → lifelong IM every 3 months

If B12 is <145 ng/L and NEUROLOGICAL symptoms present

  • Start IM hydroxocobalamin 1 mg every other day immediately
  • Do not wait for IFAB or further bloods
  • Continue every other day until symptoms stabilise or improve
  • Then continue IM every 2-3 months (lifelong if needed)

Neurological symptoms may include:

  • Pins and needles in feet or hands
  • Unsteady gait, balance issues, frequent falls
  • Numbness or burning in limbs
  • Memory issues or confusion
  • Visual disturbance (e.g. blurred vision)
  • Low mood, depression, or psychiatric changes

If B12 is 145–180 ng/L

  • Advise dietary B12 intake or consider OTC oral B12 daily
  • Check IFAB if high suspicion or mild symptoms present
  • Repeat B12 in 3 months
  • If IFAB positive → manage as pernicious anaemia
  • If asymptomatic + IFAB negative → monitor or continue OTC B12

When to Refer or Seek Specialist Advice

  • Neurological symptoms are progressing or not improving with IM therapy
  • Unclear cause (e.g. negative IFAB, not dietary)
  • No improvement in Hb after 3 months
  • Use local referral pathways (Consultant Connect, ERS)

References

mypanotes