• Vitamin deficiency usually develops slowly over several months to years
• Vitamin deficiency signs and symptoms may be subtle at first
• increase as the deficiency worsens

Symptoms

Neurological

• Numbness or paraesthesia
• Muscle weakness
• Unsteady movements

Megaloblastic anaemia

• Breathlessness
• Fatigue
• Dizziness

Non-specific

• Memory loss
• Personality changes
• Mental confusion or forgetfulness
• Irregular heartbeats

Signs

• Pale or yellowish skin
• Glossitis
• Peripheral neuropathy
• especially proprioception
• Sub-acute combined degeneration of the cord
• which may occur in the absence of anaemia

Assessment

• Diet
• Features of malabsorption
• Personal/FH of autoimmune conditions
• GI surgery
• Medication use
• e.g. proton pump inhibitors, metformin, OCP
• Pregnancy and OCP
• oestrogen reduces serum B₁₂ (but not functional B₁₂)
• by 25% on oral contraceptive pill
• by <30% by third trimester of pregnancy
• level >150 pg/mL may therefore be normal

Investigations

• FBC
• Folate
• Serum cobalamin (B₁₂)
• Anti-intrinsic factor Ab (anti-IF Ab)
• if suspect PA, test for anti-IFAB regardless of cobalamin levels

Pancytopenia

Refer to haematology

Symptoms/signs of B₁₂ deficiency present

B₁₂ low but symptoms/signs absent

• B₁₂ ≤200 pg/mL
• Non-specific symptoms

Pernicious anaemia

• Prescribe vitamin B₁₂ as hydroxocobalamin
• Treatment regimens are dependent on symptoms/signs. See BNF

Dietary cause

• Dietary sources of B₁₂ include eggs, milk/dairy products, salmon, fortified products e.g. cereals
• In the absence of neuropathy, consider oral cyanocobalamin 50-150 microgram daily taken between meals (although higher doses may be required)
• check B₁₂ levels at 1-3 months
• Duration of B₁₂ supplementation depends on the cause of the deficiency and response
• When using oral cyanocobalamin, caution regarding possible emerging PA

RBC transfusion in chronic anaemia

• If severe symptoms of anaemia, discuss with haematology before initiating transfusion which is rarely required

• If patient receiving IM hydroxocobalamin, do not routinely check B₁₂ levels
• Monitor for hypokalaemia after commencing B₁₂ replacement and consider replacement
• If PA, assess reticulocyte response at 7-10 days
• suboptimal response may indicate concomitant iron deficiency

• Inform GP of:
  • cause
  • treatment
  • monitoring required