is there a way to find out what nutrients or vitamins my body is lacking?

Answer 1

Any regular physician can test your blood and tell you exactly what your body is lacking. You don't have to go to some fancy lab in San Francisco. Make an appointment for a physical and ask you doctor to test your blood. Easy peasy japaneasy! (nothing racial intended)

Answer 2

Balco Labs in the Bay Area does exactly this. Although it was implicated in the Barry Bonds steroid scandal they do provide a valuable service by analyzing what an athletes body lacks in regards to vitamins and minerals. They then concoct a personal supplement directed at fixing what an individual is lacking in.