What is the treatment and management for a 68-year-old patient with a serum active B12 level indicating deficiency?

Treatment for Vitamin B12 Deficiency in a 68-Year-Old Patient

For a 68-year-old patient with low serum active B12 levels, treatment with intramuscular hydroxocobalamin 1 mg three times a week for 2 weeks, followed by maintenance therapy of 1 mg every 2-3 months for life is recommended. 1

Diagnosis Confirmation

• Low serum active B12 (holotranscobalamin) is a more accurate test than total B12 for vitamin B12 deficiency as it measures the biologically active form available for cellular use 1
• Consider measuring methylmalonic acid (MMA) as a confirmatory test if initial results are indeterminate 1
• Clinical B12 deficiency is diagnosed when low serum cobalamin levels (<148 pM) are accompanied by elevated functional biomarkers (homocysteine >15 μM or methylmalonic acid >270 μM) plus macrocytosis and/or neurological symptoms 1

Treatment Protocol

For patients WITHOUT neurological involvement:

• Administer hydroxocobalamin 1 mg intramuscularly three times a week for 2 weeks 1
• Follow with maintenance treatment of 1 mg intramuscularly every 2-3 months for life 1, 2

For patients WITH neurological involvement:

• Administer hydroxocobalamin 1 mg intramuscularly on alternate days until no further improvement is observed 1
• Then continue with 1 mg intramuscularly every 2 months 1
• Seek urgent specialist advice from a neurologist and hematologist 1

Alternative oral therapy:

• High-dose oral vitamin B12 (1000-2000 mcg daily) may be effective in patients with normal intestinal absorption 3, 4, 5
• However, parenteral administration remains the reference standard, especially for patients with malabsorption 1, 6

Special Considerations

• Check for folic acid deficiency before initiating B12 treatment, as B12 deficiency must be treated first to avoid precipitating subacute combined degeneration of the spinal cord 1
• In patients with Crohn's disease who have had >20 cm of distal ileum resected, prophylactic vitamin B12 (1000 mg monthly) is required indefinitely 1
• Patients taking certain medications (metformin, proton pump inhibitors, H2 receptor antagonists) have increased risk of B12 deficiency and may require more frequent monitoring 1, 7
• Older adults (>75 years) have higher prevalence of B12 deficiency and may benefit from more aggressive supplementation 5, 7

Monitoring

• Follow-up with serum B12 levels after 3 months of treatment 6
• Monitor for clinical improvement in symptoms such as fatigue, cognitive difficulties, and neurological symptoms 1, 5
• Titration of injection frequency should be based on clinical response rather than serum B12 levels alone 6

Common Pitfalls to Avoid

• Do not administer folic acid before correcting B12 deficiency, as this may mask B12 deficiency and worsen neurological complications 1
• Do not use the intravenous route for B12 administration as most of the vitamin will be lost in the urine 3, 2
• Do not assume normal serum B12 levels rule out deficiency; metabolic B12 deficiency can occur with normal serum levels 1
• Do not discontinue treatment prematurely, as maintenance therapy is typically required for life in cases of malabsorption 1