Pharmacogenomics is the study of gene expression on the enzymes used to metabolize certain medications. These enzymes help break down the medications into substances that can be more easily excreted by the body. However, in some cases these substances can be active, and some are even harmful before they are excreted. This partially explains why some people will get no effect at all while others end up in the hospital with severe side effects from the same medication at the same dose. These enzymes influence how effective a drug might be for you and how likely you are to experience negative side effects. Pharmacogenetic testing can tell us if you will make more or significantly less of a enzyme and which mediations may work better for based on your production of those enzymes. The result guide the selection of the right medication with the least side effects.