B12 levels may test in the normal range but you still may be deficient. Methylmalonic Acid and Homocysteine are two additional tests that should be run to determine effectiveness of B vitamins - if any one of B12, B6, or Folic Acid are low, then one or both of these tests may be abnormal despite normal B vitamin levels. Also, it never hurts to take a daily multi-vitamin - B vitamins are water-soluble and thus hard to overdose on when taken at RDA levels. And there isn't any known bad effect of taking very high doses of B12 frequently (other than possible insomnia).
Gluten & Sulfite Sensitivity, Many Food/Inhalant/Medication Allergies, Asthma, Gut issues (dysmotility, non-specific inflammation), UCTD (Lupus?), Osteoporosis, Anemia, T- & B-Cell Lymphopenia, malabsorption/malnutrition, ?Lyme Disease (Igenex Lab IgM WesternBlot positive), etc.
Meds: Pulmicort, Injectable Vitamin B12, Herbs, Nutritional Supplements, Homeopathy.