If I took vitamin B12 injections and folic acid along with magnesium, a B complex, and carnitine, but there was no improvement and my condition actually worsened with increased anxiety, does this mean Feeling worse after B12 Injection: Answering concerns. La Vie Med Spa You might need a B12 injection if you're constantly feeling tired, run down, or low on energy. B12 supports energy levels, metabolism, mood, and neurological health. to help your body feel its Vitamin B12 for Anxiety & Mood: What Science Says