nutritional disorders
Vitamin B12 Deficiency
Treatment of Vitamin B12 Deficiency
Supplemental vitamin B12 Vitamin B12 1000 to 2000 mcg orally can be given once a day to patients who do not have severe deficiency or neurologic symptoms or signs. A nasal gel preparation of vitamin B12 is available at a higher price. Large oral doses can be absorbed by mass action, even when intrinsic factor is absent. If the methylmalonic acid (MMA) level (sometimes used to monitor treatment) does not decrease, patients may not be taking vitamin B12. For more severe deficiency, vitamin B12 1 mg IM is usually given 1 to 4 times a week for several weeks until hematologic abnormalities are corrected; then it is given once a month. Although hematologic abnormalities are usually corrected within 6 weeks (reticulocyte count should improve within 1 week), resolution of neurologic symptoms may take much longer. Neurologic symptoms that persist for months or years become irreversible. In most older people with vitamin B12 deficiency and dementia, cognition does not improve after treatment. Vitamin B12 treatment must be continued for life unless the pathophysiologic mechanism for the deficiency is corrected. Infants of vegan mothers should receive supplemental vitamin B12 from birth. 