It is called pharmacogenetic testing..they take two samples by swabing both sides of the insides of u cheek with q tips..results n bout two weeks..they are able to tell if your body will or won't accept a big Ol list of meds..and how fast your body metabolizes..the slower the metabolic rate..the more side effects predicted..ya still have to watch for side effects..but it can save ya a whole lotta trouble eliminating ones the paperwork says adverse reactions to..the other swab is to check your serotonin receptors..in my case I have a gene that makes depression difficult to treat as well as another gene that won't process ssri's..