where to inject b12 intramuscular How Give a Injection: Step-By-Step Instructions Vitamin B12 Injection Sites: All
Description
According to Mayo Clinic.org , vitamin B12 (cobalamin) plays an essential role in the formation of red blood cells, cell metabolism, nerve function and the production of DNA

Ultrasound helps confirm the exact location of the needle, ensuring its placed in the right spot without damaging surrounding structures

Gluten-free shouldnt be an issue
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It suggests to me that you were given it when you didn't need it and if this is the case I'm not surprised at your skin's reaction
