Several of my elderly patients (older than age 75 years) were initially vitamin B12-deficient. A few months after treatment with oral and/or intramuscular supplements, laboratory reports showed B12 levels above the reported reference range. What are the implications of this elevation? What could have caused this drastic increase, and what course of action is required?—BARBARA VASSALLO, NP, Willingboro, N.J.

As a water-soluble vitamin, B12 does not put patients at risk, as do such fat-soluble vitamins as A, D, and K. There is no one set of guidelines for B12 replacement, and depending on the level of absorption, patients can respond quickly to supplementation. The most common cause of B12 deficiency in the elderly is malabsorption (older stomachs do not produce as much acid, which is crucial to B12 metabolism). Malabsorption can also be caused by prolonged use of proton pump inhibitors, metformin, and gastric bypass, as well as iliectomy (common in patients suffering from Crohn’s disease). Since B12 deficiency can cause significant—and after a time, irreversible—neurologic changes, it is important to identify this and address it. Patients who demonstrate such neurologic changes as burning feet, sore tongue, loss of balance, and memory loss should receive 1,000 μg intramuscular B12 weekly for four weeks and then monthly for four to six months. This gives the best chance of reversing neurologic impairment. For those who are asymptomatic or have subtle symptoms, oral supplementation is sufficient: 1,000 μg b.i.d. for two weeks and then daily thereafter. It is reasonable to recheck B12 levels after three to six months.—Rebecca H. Bryan, APRN, CNP, Lecturer, Family Health Nurse Practitioner Program, University of Pennsylvania School of Nursing, Philadelphia (148-11)