B vitamins, especially B12, are very important in energy production. most people will feel a bit more energy with a daily B complex. they are also helpful with nerve pain. if the issue is damaged nerves in the body instead of signals from the brain, mega doses of B vitamins can help the nerves heal, and reduce pain.

Get blood test for this. I’m deficient. Know where you stand

I tried a vit b 12 supplements. I didn’t have low b 12 in my blood work. You don’t need vit D unless it’s low in blood work. I knew that but thought I would try it. I was trying them for fibro fatigue. They didn’t help.

This can help but only if you are low in the first place it wont help if you aren't low in this in your body and diet.

Ever since I can remember I have had low vitamin b12. They finally agreed to let me have a course of weekly vital b12 injections weekly on the NHS but they made no difference. I still have low levels and still feel exhausted all the time