B12 Deficiency – Finding the Cause of Malabsorption

Step 1 – Confirm B12 Deficiency

• Vitamin B12
• CBC + MCV + Peripheral Smear
• Methylmalonic Acid (MMA)
• Serum Folate
• Iron Studies (Ferritin, Iron, TIBC, Transferrin Saturation)

Step 2 – Check for Intrinsic Factor Problems

• Intrinsic Factor Antibody ⭐ (Most important)
• Parietal Cell Antibody

Step 3 – Check for Other Absorption Disorders

• Celiac Disease Panel

  • Tissue Transglutaminase IgA (tTG-IgA)
  • Total IgA

• Gastroscopy (Endoscopy) with biopsy (if advised by gastroenterologist)

Step 4 – If Symptoms Suggest Other Causes

• SIBO Breath Test
• Fecal Calprotectin
• Colonoscopy (if indicated)
• Small Bowel Imaging (if indicated)

Additional Helpful Tests

• Vitamin D
• TSH (Thyroid Profile)
• Comprehensive Metabolic Panel (CMP)

My Testing Priority

1. Vitamin B12
2. CBC + MCV
3. Methylmalonic Acid (MMA)
4. Intrinsic Factor Antibody
5. Parietal Cell Antibody
6. Folate
7. Iron Studies
8. Celiac Panel
9. Gastroscopy (if needed)

Key Point: If B12 intake is adequate (eggs, meat, fish) but deficiency persists, think malabsorption rather than low intake. Start with blood tests before moving to invasive investigations.