Speaking of which, I think it's a great idea for everyone to get their vitamin levels checked. Your doctor is unlikely to order such a blood test unless you are in an extreme situation, but it's cheap (around $100) to get a pretty extensive panel done.

I did it recently and found out basically all my b vitamins were in the toilet along with my vitamin D level. I started taking a b complex vitamin and D3 supplement and found immediate improvements to brain fog and exhaustion.