I get an annual every year for around $150 and can request any test that I want from my doctor. I don't think this is something you need to test more often than that unless you have huge swings in your diet. Obviously if low levels of something are detected there are follow ups. I was actually low on vitamin d (by quite a lot) and started taking supplements. However, I do wish it was easier to get medical tests as you suggest without a doctors orders.