You have asked a very interesting question. The fact that you are going for biochemical genetics testing means that you must have some abnormality or symptom that your doctors
have not been able to diagnose. I will try to lay out some of the possibilities here.
There are a series of disease that are acquired before birth where an enzyme or other biochemical molecule is missing from your genetic makeup. There are dozens of these disease with many different syndromes, and symptoms that effect many different organs. They effect they way the body stores energy, stores waste, and deals with other molecules. Many of them (possibly most of them) are fatal in the first few years of life. Since you have made it to age 28, you don't have one of those. Other than that, I can't tell you much more without knowing why the testing was initiated in the first place.
The best physician for you to see first is your primary care physician
. He or she will be able to explain the results of the biochemical genetics testing in a way that you should be able to understand what to expect. In addition, you will be able to get a referral to a specialist appropriate for the condition you have (if you are diagnosed with anything). Good luck.