All of my doctors (due to moves, retirements, etc) have done this for years in the US. When the topic came up recently at a get together everyone could recall

All of my doctors (due to moves, retirements, etc) have done this for years in the US. When the topic came up recently at a get together everyone could recall their relative Vitamin D levels (too low, normal) from recent checkups. It’s common, at least in the US areas where I’ve lived.