Therapy
Usually, 1 mg/day of cobalamin given intramuscularly for a week, followed by 1 mg/week for
four weeks and then 1 mg/month for life, is an appropriate therapeutic regimen. Obviously, therapy
should be started after the vitamin deficiency has been established and the causes thoroughly looked
for. Oral daily doses of 1–2 mg seem also to be suitable for patients refusing parenteral therapy who
have cobalamin malabsorption or pernicious anemia, provided that cobalamin stores have been rapidly
supplied by parenteral cobalamin.
Effective therapy reverses megaloblastosis in 24 h and reestablishes normal marrow hematopoiesis
in 48 h. The reticulocyte count increases after 3–4 days and peaks after a week; hypersegmented
neutrophils remain in the peripheral blood up to two weeks. Rising red blood cell count and
hemoglobin will take one week; normalization of the complete blood count requires about eight weeks.