Anyone at any age, can become B12 deficient. However, certain people are at an elevated risk. They include the following:
Vegetarians, vegans and people eating macrobiotic diets.
People aged sixty and over
People who’ve undergone any gastric and/or intestinal surgery, including bariatric surgery for weight loss purposes (Gastric bypass).
People who regularly use proton-pump- inhibitors. H2 blockers, antacids, Metformin, and related diabetes drugs, or other medications that can interfere with B12 absorption.
People who undergo surgeries or dental procedures involving nitrous oxide, or who use the drug recreationally.
People with a history of eating disorders (anorexia or bulimia).
People with a history of alcoholism.
People with a family history of pernicious anaemia.
People diagnosed with anaemia (including iron deficiency anaemia, sickle cell anaemia and thalassaemia).
People with Crohn’s disease, irritable bowel syndrome, gluten enteropathy (celiac disease), or any other disease that cause malabsorption of nutrients.
People with autoimmune disorders (especially thyroid disorders such as Hashimoto’s thyroiditis and Grave’s disease) Type 1 diabetes, vitiligo, lupus, Addison’s disease, ulcerative colitis, infertility, acquired agammaglobulinemia, or a family history of these disorders.
Women with a history of infertility or multiple miscarriages.
You score a "hit" with one or two of the above people and your symptoms certainly point toward a possible B12 and/or Folate deficiency.
Sadly the serum B12 tests are not all that reliable and what may be "Normal" for a normal person may not apply to you as an individual.
However the British Society for Haematology (BSH) guidelines say "In the presence of discordance between the test result and strong clinical features of deficiency, treatment should not be delayed to avoid neurological impairment".
This means that your doctor should ignore the "Normal" and treat your neurological symptoms post haste and in accordacce with the N.I.C.E guidelines on the treatment for Vitamin B12 Deficiency as follows:
Treatment for B12 deficiency
How should I treat a person with vitamin B12 deficiency anaemia?
For people with neurological involvement:
Seek urgent specialist advice from a haematologist.
Ideally, management should be guided by a specialist, but if specialist advice is not immediately available, consider the following:
Initially administer hydroxocobalamin 1 mg intramuscularly on alternate days until there is no further improvement, then administer hydroxocobalamin 1 mg intramuscularly every 2 months.Make a list of your symptoms and present this to your doctor and ask him to treat you according to your symptoms and (perhaps) even start you on loading doses "until there is no further improvement" according to the guidelines Also ask to have your Folate level tested as the two work together with your iron to make red blood cells and to function properly.
I'm not a medically trained person but have had P.A. (a form of B12 deficiency) for over 45 years.