I had adequate, middle of the range vitamin d levels last time I checked in December. Likely because I was supplimenting as of UK weather in winter. However I definitely notice such a difference in mood and other health issues in summer. My fatigue, mood and libido is so much better. I understand that just the mental/emotional aspect of enjoying sunny weather can obviously help but this feels so night and day and happens every summer but not till a few months into the hot weather. I feel this might be to do with good vit d levels. My levels in winter were 104nmol/l which is fine but can it be that some people just need higher. Or is it possible to have good blood levels from supplementing in winter but the sun help me convert the vit d in a way that my body utilizes that's different from suppliments? Do blood levels always mean your fine no matter if sun or suppliments? Or can the sun do something unique?