B12 therapy also significantly changed hematologic parameters from baseline even though the patients in the study didn’t have anemia. Mean corpuscular volume, for example, decreased from 100 to 90 fL with oral therapy and 102 to 97 fL with IM therapy (P<.005 for each). Neurologic symptoms (memory loss, paresthesias, ataxia) either cleared or improved markedly in all patients. Investigators compared all parameters against baseline values but didn’t directly compare oral with IM therapy. The trial didn’t assess safety outcomes.2
Recommendations
Canada’s British Columbia Medical Association and Ministry of Health recommend oral replacement of B12 (1000-2000 mcg/d) for most cases of vitamin B12 deficiency, including pernicious anemia. For patients with neurologic symptoms, they recommend an initial B12 injection (1000 mcg IM) followed by oral replacement.3
The US Centers for Disease Control and Prevention recommends either oral (1000 mcg daily) or parenteral B12 replacement. They advise giving parenteral therapy either subcutaneously (to reduce the burning sensation) or IM (1000 mcg per week for 8 weeks, then monthly for life).4