b12 injections safe in pregnancy Building a baby takes vitamin – here's why it matters Vitamin B-12 Injections: Use, Deficiency,
Description
doi:10.1097/gme.0b013e3181732953

Those shots, which are unapproved, are sold online under the names Aqualyx, Lipodissolve, Lipo Lab and Kabelline, the FDA said
My best guess is that its because of some local damage/irritation you caused during the injection (ie

This is an autoimmune disorder caused by a lack of red blood cells when the body is not able to absorb enough vitamin B12

The most important things are a positive attitude and patience
