b12 injection 5000 mcg Vitamin (5,000 mcg/ml) [100 mL] such as Compounded Methylcobalamin (Vitamin B12) Injection,

William Castle demonstrated that gastric juice contained an "intrinsic factor" which when combined with meat ingestion resulted in absorption of the vitamin in this condition

For example, a 1 mL solution with 1000 mcg/mL is the same as 1 mg/mL

Calcium and Magnesium Dr Lapp recommended 1,000mg to 1,500mg of calcium daily and 500-750mg magnesium daily

If you combine the methyl B12 with ginkgo biloba, or L-methylfolate and pyridoxal 5-phosphate, improvements may be even better

A common question when addressing low B12 is whether an injection is actually necessary

[DOI] [PMC free article] [PubMed] [Google Scholar] Higgins 2011a Higgins JPT, Green S (editors)