Increase Energy and Combat Fatigue With A Vitamin B12 Injection Vitamin B 12 intramuscular injections are also used therapeutically to help restore energy and combat various symptoms related to such deficiencies. Vitamin B 12 is essential to the development of healthy blood cells, nerve Feeling tired, foggy, or run down? It could be a B12 deficiency Weekly B12 injections help support: Increased energy + reduced fatigue Sharper focus + better mood Boosted Is it too soon to administer another vitamin B12 (cyanocobalamin) injection to a patient with a vitamin B12 level of 308 pg mL who received an injection 6 days ago for fatigue?