There’s a programme on right now about Vitamin D on BBC2! You should be able to catch it on bbciplayer – Inside The Factory: How Our Favourite Foods Are Made.
I take Vitamin D3 10mcg daily as I’ve been more or less housebound since 2010 and don’t go outside much. I have musculoskeletal issues (arthritis). I might ask my GP about a blood test next time I see her.
I recently started taking 500u a day ..not because of what the government said but because I read that it can help with osteo pain. So I’m going try 3 months one a day and see if i Notice anything different 🙂