When you take a medicine (or a drug), your body needs to find a way to use it. Some proteins in your body break down (or metabolize) medicines. Breaking down a medicine can make it more or less active, based on the medicine. If you break down a medicine too fast or too slowly, this may cause the medicine to not work as well or it may cause a side effect.
Cytochrome P450 is a family of proteins that helps your body break down certain medicines. Cytochrome P450 family 2 subfamily C member 19 (CYP2C19) (say “SIP-2-see-19”) is one certain protein in this family. It is the job of CYP2C19 to break down some medicines we use.
By testing your DNA, we can find DNA differences that can help us to see how well your CYP2C19 protein may work in you. The results of this test can help your doctor choose a certain medicine or a certain dose of medicine that is right for you. The results of your CYP2C19 gene test will place you into one of 5 groups:
| Metabolizer Type | Description |
| Normal Metabolizer | People in the group likely have normal working CYP2C19 proteins. |
| Poor Metabolizer | People in this group likely have very little or no active CYP2C19 proteins. People who are poor metabolizers may break down some medicines more slowly.
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| Intermediate Metabolizer | People in this group likely have reduced activity of CYP2C19 proteins. People who are intermediate metabolizers may break down some medicines at a rate in between the poor and normal metabolizers. |
| Rapid Metabolizer | People in this group likely have high activity of CYP2C19 proteins. People who are rapid metabolizers may break down some medicines more quickly. |
| Ultrarapid Metabolizer | People in this group likely have very high activity of CYP2C19 proteins. People who are ultrarapid metabolizers may break down some medicines more quickly. |
