do b12 injections cause headaches Why I feel worse after a injection? Vitamin B12 Deficiency Anemia: Symptoms,

It depends on how bad your deficiency is and how you react to treatment

Some patients feel as though they want more frequent injections, and occasionally we test levels to see if they are receiving adequate replacement, but Im not sure how strong the evidence is to support this. GPs should consider periodic vitamin B12 testing of higher-risk patients who take metformin, even if they dont display symptoms of deficiency, the UK medicines regulator said earlier this year

Adjusting the Normal Dose of B12 Injection for Severe Cases For severe vitamin B12 deficiency, higher doses might be needed to quickly fill up body stores

You can get Vitamin B12 shots in three ways: intramuscularly (IM), subcutaneously, or intravenously (IV)