You might also try a B-complex vs
B12 only. All of the B vitamins
have to be present in adequate amounts, because they work together. Calcium and magnesium levels also have a bearing on energy. Calcium is calming, so can help you sleep better. I take mine at night.
There are so many things that affect our energy levels, it's really hard to pinpoint one single thing. There's the amount of sleep you get, weight, exercise, the types of food you eat.. It all affects our energy.