injections of vitamin b12 are used successfully to treat Monthly Injection: Typical Dose & Schedule Best Vitamin B12 Injection Site:

However, a study found that taking 1,000 mcg of B12 by mouth or injecting the vitamin achieved similar results in treating the deficiencies

Type 1 pernicious anemia It is brought on by an autoimmune condition that impairs the stomach's ability to produce intrinsic factor, a protein required for vitamin B12 absorption

Disclaimer: Compounded medications are not FDA-approved

[DOI] [PMC free article] [PubMed] [Google Scholar] 31.Tian L.-W., Luo D., Chen D., Zhou H., Zhang X.-C., Yang X.-L., Wang Y.-L., Liu W

The withdrawal of whole blood is permitted for the purpose of separating and locally re-inject platelet-rich plasma

The catch is that your body cant store these vitamins for later use, meaning you need a more frequent intake to ensure you arent deficient in water-soluble vitamins