I would call my lovely Poland less and less a civilised world, but even here I can test whatever I want whenever I want in at least two big networks of private labs. I go to lab online shop, buy what I want (vit D costs ~$13), download a voucher with qr code on my phone, go to the lab and 5 mins later I can go to home. I have an account on their web app, later that day I have results and can compare it to all my previous results too, each thing with nicely visualised historical data on diagram.