hit a vein while injecting b12 What Happens If You Inject Wrong? · PA Relief Best Vitamin B12 Injection Sites
Description
The AAFP advises that injectable therapy leads to more rapid improvement and should be considered in patients with severe deficiency or severe neurologic symptoms (Langan RC, Goodbred AJ, 2017)

When performed, this test can diagnose and show the extent of nerve injury
Low potassium levels (hypokalemia) This may occur after rapid correction of severe B12 deficiency

Nutr., 6 , 93

A small amount of iron may be through the urine and feces cleared