Why am I asking this question on a Q board? Because Q people are probably a lot smarter than the other internet forums I frequent. Besides that, I don't think Q would mind anyway.
The vitamins subject is a deep rabbit hole. I don't have time to go down that rabbit hole, so I figure starting a thread and asking the Q community would be way quicker.
I've been feeling tired all the time for several weeks now. I'll throw in fatigued and lethargic too. I've got my mind made up that it's a vitamin deficiency. I think all of us could benefit from this knowledge about vitamins. I've heard that taking vitamin D3 can boost energy levels. What other vitamins are important?
Niacin is great. It completely wiped out restless leg syndrome with my first dose 2 years ago. As side benefits I no longer get drowsy during the day, I'm now far more alert during all my waking hours. Iodine, from which the thyroid hormone is produced, is now deficient in the American diet, leading to sub-grade thyroid hormone. Supplementation of Iodine should quickly lessen lethargy and fatigue as good thyroide hormone leads to improved mitochondial action at the cellular level. After 4 major surgeries Iodine did the most to put back the fire in my life. Many of the other recommendations below are also a part of my personal daily supplements. Try any/all and see what works for you.