It's simple really. Have your doctor take a blood sample, get it tested for vitamin D deficiency and regulate your intake accordingly. I've had myself tested d

It's simple really. Have your doctor take a blood sample, get it tested for vitamin D deficiency and regulate your intake accordingly. I've had myself tested december last year, mostly out of curiosity. Turns out I was severly deficient. Not really surprising, being a vegetarian locked inside. Started taking the highest available dosage (20000) via prescription twice per week and now feel much more energetic and "awake" I think. I've had another test a few weeks ago, and while there's no acute deficiency anymore, doc suggested keeping up the current intake for another few months.