Catching a five-pound regain is far easier to address than a twenty-pound regain
Without the dietary component, they produce nothing measurable

monitoring may be required Polycythemia vera: Correcting B12 deficiency may unmask underlying polycythemia Masking folate deficiency: B12 supplementation can mask the hematologic signs of folate deficiency while allowing neurological damage to progress Allergic reactions: Rare hypersensitivity reactions have been reported, including anaphylactic shock with cyanocobalamin Common Side Effects Mild diarrhea Injection site reactions: pain, swelling, itching Feeling of generalized body swelling Mild headache Temporary reddish urine (normal B12 is water-soluble and excreted) Seek Medical Attention For Signs of serious allergic reaction: rash, hives, facial swelling, difficulty breathing Chest pain or irregular heartbeat Signs of low potassium: muscle cramps, weakness, irregular heartbeat Vision changes (especially if you have Lebers disease) Drug Interactions Chloramphenicol: May antagonize the hematopoietic response to B12 Metformin, proton pump inhibitors, H2 blockers: Can reduce B12 absorption (these are reasons to use injectable B12 instead of oral) Nitrous oxide: Can inactivate B12 in the body Use in Pregnancy and Breastfeeding B12 is generally considered safe during pregnancy and breastfeeding when used at appropriate doses

Whether those 5 lbs are worth the higher side effect burden at 12mg is a personal decision
The cost of not covering these medications will be far greater in the long run.