Oral contraceptives can cause falsely low vitamin B(12) levels

Acta Haematol. 2000;104(1):22-4. doi: 10.1159/000041064.


Serum vitamin B(12) radioimmunoassays may give falsely low results in patients with folate deficiency, multiple myeloma, megadose of vitamin C and following radioisotope organ scan. We evaluated 10 consecutive healthy women on oral contraceptives (OC) who had falsely low vitamin B(12) levels, as reflected by normal urine methylmalonic acid and plasma homocysteine. After 1-month cessation of OCs, vitamin B(12) returned to the normal range in all women. Transcobalamin I (TCI) blood level was decreased in 60% of patients. OCs may cause temporary low vitamin B(12) blood levels of no clinical significance that can be associated with low TCI levels

MeSH terms

  • Adult
  • Contraceptives, Oral / administration & dosage
  • Contraceptives, Oral / adverse effects*
  • Contraceptives, Oral / blood
  • Diagnostic Errors
  • False Positive Reactions
  • Female
  • Homocysteine / blood
  • Humans
  • Methylmalonic Acid / urine
  • Transcobalamins / drug effects
  • Transcobalamins / metabolism
  • Vitamin B 12 Deficiency / diagnosis*
  • Vitamin B 12 Deficiency / etiology


  • Contraceptives, Oral
  • Transcobalamins
  • Homocysteine
  • Methylmalonic Acid