Need conventional B-12 replacement, want insurance to pay, don’t mind monthly shots | Cyanocobalamin (1 mg IM/SC monthly) | Readily stocked; CPT J3420 billing; lowest cost. |
Want the fewest injections and can obtain product (or live in EU/UK) | Hydroxocobalamin (1 mg IM every 8–12 weeks once replete) | Superior tissue retention; accepted first-line abroad. |
Are targeting peripheral neuropathy or high-dose “neuroprotection” and self-pay is OK | Methylcobalamin (5–10 mg SC two-three times weekly) | Small trials show symptom and nerve-conduction benefits at supraphysiologic doses; patients often tolerate large SC doses well (Safety and efficacy of intravenous ultra-high dose methylcobalamin ..., Methylcobalamin as a candidate for chronic peripheral neuropathic ...). |
Treating cyanide poisoning or severe nitroprusside toxicity | Hydroxocobalamin 5 g IV | Only formulation FDA-approved for this indication. |
Have chronic kidney disease and worry about added cyanide moiety | Either hydroxo- or methyl-… | They lack the cyanide ligand present in cyano; no large trials show harm, but many nephrologists prefer cyanide-free forms. |