PMID 19713987
Our post on PCOS and hair thinning discusses how to distinguish nutritional causes from hormonal ones
For those with irreversible causes such as pernicious anaemia or malabsorption, injections are usually given every 23 months

Category : HUMAN PRESCRIPTION DRUG LABEL DEA Schedule : none Marketing Status : New Drug Application INGREDIENTS AND APPEARANCE LABELER - Hikma Pharmaceuticals USA Inc.(001230762) PRINCIPAL DISPLAY PANEL NDC 0143-9621-01 1 mL Vial Cyanocobalamin Injection, USP Rx only 1,000 mcg/mL For IM or SC use ONLY Protect from light Contains Benzyl Alcohol NDC 0143-9621-25 Rx only Cyanocobalamin Injection, USP 1,000 mcg/mL For Intramuscular or Subcutaneous use ONLY Contains Benzyl Alcohol as a Preservative 25 x 1 mL Vials PRINCIPAL DISPLAY PANEL NDC 0143-9620-01 10 mL Multiple Dose Vial Cyanocobalamin Injection, USP Rx only 10,000 mcg per 10 mL (1,000 mcg/mL) For Intramuscular or Subcutaneous use ONLY Contains Benzyl Alcohol as a Preservative NDC 0143-9620-10 Rx only Cyanocobalamin Injection, USP 10,000 mcg per 10 mL (1,000 mcg/mL) For Intramuscular or Subcutaneous use ONLY Contains Benzyl Alcohol as a Preservative 10 x 10 mL Multiple Dose Vials PRINCIPAL DISPLAY PANEL NDC 0143-9619-01 30 mL Multiple Dose Vial Cyanocobalamin Injection, USP Rx only 30,000 mcg per 30 mL (1,000 mcg/mL) For Intramuscular or Subcutaneous use ONLY Contains Benzyl Alcohol as a Preservative NDC 0143-9619-10 Rx only Cyanocobalamin Injection, USP 30,000 mcg per 30 mL (1,000 mcg/mL) For Intramuscular or Subcutaneous use ONLY Contains Benzyl Alcohol as a Preservative 10 x 30 mL Multiple Dose Vials NDC 0143-9619-01 Rx only Cyanocobalamin Injection, USP 30,000 mcg per 30 mL (1,000 mcg/mL) For Intramuscular or Subcutaneous use ONLY Contains Benzyl Alcohol as a Preservative 1 x 30 mL Multiple Dose Vials PRINCIPAL DISPLAY PANEL

Self injection with sub cut
Choosing between Vitamin B12 Injections and oral supplements ultimately depends on your health status, lifestyle, and personal preferences