A 36-year-old man presents to your office complaining of generalized weakness, and a ‘pins and needles’ feeling in his hands and feet. He wakes up from sleep due to tingling sensations in his fingers. On physical examination, you note that he is ataxic and has decreased vibration and position sense in both his arms and legs. He has decreased sensitivity to light touch, pinprick and vibration. Deep tendon reflexes are hypoactive. The Romberg test is positive. He drinks 1 or two drinks a day. His past medical history is significant for celiac disease and dermatitis herpetiformis. Laboratory tests reveal macrocytic anemia with mean corpuscular volume of 105 fl. Peripheral smear shows macro-ovalocytes, hypersegmented neutrophils, and anisopoikilocytosis. He also has a positive Schilling test. Next best step in the management of this patient?
