Why Does Nitrous Oxide Cause B12 Deficiency? [2026 Update] King Law Vitamin B12 deficiency, sometimes called cobalamin deficiency, happens when your body is either not getting enough or not absorbing enough vitamin B12 from the foods you eat. Vitamin B12 is an important Consequences of Excess or Deficiency of Vitamin B12 Vinmec Cyanocobalamin Injection: Vitamin B12 Deficiency Relief Mountainside Medical Vitamin B12 deficiency is more common than you think Frequent urination, tingling or burning in feet, numbness in hands & feet, cracked lips or tongue sores these are NOT normal