Main benefits of B12 injections 1) Increased energy & reduced fatigue B12 helps convert food into usable energy Deficiency often causes tiredness, weakness, and low stamina 2) Healthy red blood cells Prevents B12 Injections: Who Should Get Them and How Long Do They Last? Vitamin B12 Injections: Boost Energy & Support Weight Loss B12 Shots Dosage for Adults: How Much, How Often, and Key Injection Guidelines Liv Hospital Could you be low on Vitamin B12? It's more common than you think, and often overlooked. Signs may include: Headaches Lightheadedness Sore tongue Difficulty concentrating Low mood Fatigue Lethargy A little insight to the importance of the b12 injections. My client hadn't been feeling well & had some bloods done with her GP. The results identified a severe deficiency in b12.