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 Vitamin B12 deficiency can cause symptoms like headaches, fatigue, depressive mood, gastrointestinal issues, and more. While vegetarians are at a higher risk of vitamin B12 deficiency, it can affect non vegetarians too. Check Why Do I Feel Worse After My B12 Injection? PA Relief Feeling tired, foggy, or low on energy? Vitamin B12 plays an important role in keeping your body functioning at its best. B12 injections may help: Individuals with low B12 levels