Vitamin B12 deficiency has been linked to fatigue, tingling or loss of feeling in the extremities, irritability, memory impairment, depression, anemia, irritable bowel syndrome (IBS), constipation, poor wound healing, dry or damaged looking skin, and neurological disorders
Incidentally, the healthy reference range is 191-663 pg/ml and correlates closely with oral cobalamin intake, which is why the vitamin B12 blood level alone is not an adequate parameter to diagnose a deficiency (Herrmann and Obeid, 2014)
Patients should contact their GP urgently if neurological symptoms worsen, new symptoms develop, or signs of liver decompensation appear, as this may indicate inadequate treatment response or disease progression requiring specialist review
Cobalamin deficiencies or a lack of Vitamin B12 can also lead to issues such as anemia or the feeling of fatigue and cognitive problems in most people