B12 is critical and so many, I'm sure are low, and I've known of many who even went for B12 injections. I think I did one of those years ago, but I take B12 methylcob daily for many years and my B12 levels are HIGH, but fatigue still continues and pain is chronic fatigue as I see it now later with all my issues. I was a ball of fire before menopause and I know thyroid is also big with fatigue...so many are mis-dx'd and under treated or not treated for sluggish thyroid...I was one of them for 10 miserable years from 1991 to 2002. Thyroid addresses some 60+ health issues.