NCLEX Review Guide: Vitamin B12 Deficiency

Understanding B12 Deficiency

• Vitamin B12 (cobalamin) is essential for DNA synthesis, red blood cell formation, and neurological function. Deficiency leads to megaloblastic anemia and neurological complications.
• B12 requires intrinsic factor from gastric parietal cells for absorption in the terminal ileum. Without intrinsic factor, pernicious anemia develops.
• Body stores of B12 can last 3-5 years, so deficiency develops gradually and symptoms may be subtle initially.

Signs & Symptoms

• Hematological: Fatigue, weakness, pallor, dyspnea on exertion due to megaloblastic anemia with large, immature RBCs.
• Neurological: Paresthesias in hands/feet, loss of position and vibration sense, ataxia, memory problems, and potential irreversible spinal cord damage.
• GI symptoms: Smooth, beefy red tongue (glossitis), loss of appetite, weight loss, and diarrhea.
• Psychiatric symptoms may include depression, confusion, and in severe cases, dementia-like symptoms.

Laboratory Values & Interventions

• Serum B12 level <200 pg/mL indicates deficiency; levels 200-300 pg/mL may require additional testing like methylmalonic acid levels.
• Complete blood count shows macrocytic anemia with MCV >100 fL and hypersegmented neutrophils on peripheral smear.
• Schilling test (rarely used now) or anti-intrinsic factor antibodies help diagnose pernicious anemia.
• Treatment involves cyanocobalamin injections initially, then oral supplementation once B12 stores are replenished.

1. Administer initial B12 injections (1000 mcg IM) daily for 1 week
2. Continue weekly injections for 4 weeks
3. Maintain with monthly injections or high-dose oral supplements
4. Monitor CBC and B12 levels to assess response

Priority Interventions

• Monitor for falls risk due to neurological symptoms like ataxia and decreased position sense.
• Assess nutritional status and provide education about B12-rich foods (meat, fish, dairy, fortified cereals).
• Teach proper injection technique if patient will self-administer B12 injections at home.
• Monitor for improvement in energy levels and neurological symptoms, which may take weeks to months.

Quick Check Questions

• □ Can you list 3 neurological symptoms of B12 deficiency?
• □ Do you know the difference between B12 and folate deficiency?
• □ Can you explain why IM injections are initially required?
• □ Do you understand the role of intrinsic factor?