What are the common causes of vitamin B12 deficiency in a young adult female?

Common Causes of Vitamin B12 Deficiency in a 26-Year-Old Female

The most common causes of vitamin B12 deficiency in a young adult female include inadequate dietary intake (especially in vegetarians/vegans), malabsorption issues, medication use, and certain autoimmune conditions. 1, 2

Primary Causes

• Dietary factors:

  • Vegetarian or vegan diet - B12 is not present in foods of plant origin, making strict vegetarians who consume no animal products (including milk or eggs) at high risk 3, 1
  • Poor consumption of B12-rich foods (meat, dairy, eggs, fortified cereals) 1, 4

• Malabsorption conditions:

  • Food-bound malabsorption - inability to release B12 from food proteins 5, 6
  • Atrophic gastritis affecting the gastric body 7, 6
  • Autoimmune gastritis (pernicious anemia) - lack of intrinsic factor needed for B12 absorption 8, 3
  • Inflammatory bowel disease 2
  • History of bariatric surgery or other gastrointestinal surgeries 2, 9

• Medication-induced deficiency:

  • Proton pump inhibitors or H2 blockers (especially if used >12 months) 7, 2
  • Metformin (especially if used >4 months) 7, 2
  • Other medications: colchicine, anticonvulsants, sulfasalazine, methotrexate 10, 7

• Autoimmune conditions:

  • Thyroid disease, type 1 diabetes 7
  • Autoimmune gastritis with anti-intrinsic factor antibodies 8, 3

Diagnostic Considerations

• Laboratory assessment:

  • Initial testing should include complete blood count and serum vitamin B12 level 2, 4
  • B12 levels <180 pg/mL are diagnostic for deficiency 4
  • For borderline levels (180-350 pg/mL), methylmalonic acid (MMA) measurement is recommended 7, 4
  • Standard total B12 tests may not accurately reflect biologically active B12 7

• Additional testing for unclear cases:

  • Consider testing for Helicobacter pylori and autoantibodies associated with autoimmune gastritis 4
  • Topographical biopsies may be needed to determine anatomic extent and histologic severity 8

Treatment Approach

• Supplementation:

  • Oral high-dose vitamin B12 (1-2 mg daily) is effective for most patients 2, 9
  • Intramuscular therapy should be considered for severe deficiency or neurological symptoms 3, 2
  • For vegetarians/vegans: daily supplementation or consumption of fortified foods is recommended 3, 2

• Monitoring:

  • Follow-up B12 levels and complete blood count to ensure adequate response 3
  • Long-term supplementation is often required, especially if the underlying cause cannot be corrected 9

Important Considerations

• Vitamin B12 deficiency left untreated for more than 3 months may produce permanent degenerative lesions of the spinal cord 3
• Folic acid supplementation may mask B12 deficiency symptoms while allowing neurological damage to progress 3
• Early diagnosis and treatment are essential to prevent irreversible neurological complications 9

Remember that young women may have increased B12 requirements during pregnancy and lactation, making adequate diagnosis and treatment particularly important in this population 3.