Several online Canada-based pharmacies offer prescription B12 injections for sale, including CanadaPharmacyOnline.com, CanadaDrugs.com, CanadaDrugSuperstore.com and B12-Shot.com. B12 is responsible for carrying oxygen throughout the body, and a deficiency can cause anemia, states WebMD. This condition occurs when the digestive system does not absorb enough of the vitamin.
Those who have a condition called pernicious anemia have cells in the stomach that destroy B12, states WebMD. Those with celiac disease, Crohn's disease, excessive bacteria growth in the small intestine or parasites can also develop a B12 deficiency. The daily recommended dose of B12 for those 14 and older is 2.4 micrograms, while women who are pregnant or breastfeeding require more.