Vitamin B12 Deficiency
What Is It?
Deficiency of vitamin B12 causing megaloblastic anemia, peripheral neuropathy, subacute combined degeneration of the spinal cord, and cognitive impairment. Common in vegans, elderly, and those on metformin or PPIs.
How Is It Diagnosed?
Serum B12 <200 pg/mL (borderline 200-300). Elevated methylmalonic acid and homocysteine confirm functional deficiency.
How Is It Treated?
Intramuscular B12 (cyanocobalamin) 1,000 mcg weekly x4, then monthly. High-dose oral B12 (1,000-2,000 mcg daily) equally effective for many patients. Dietary counseling.
Tests and Imaging Typically Needed
CBC, serum B12, methylmalonic acid, homocysteine, peripheral smear, intrinsic factor antibodies if pernicious anemia suspected.
Approximate Self-Pay Costs
Office visit: $95-$150. B12 level: $20-$35. IM B12 injections: $10-$25 each. High-dose oral B12: $5-$10/month.