When you take a medicine (or 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 kind of medicine.  If your body breaks down a medicine too fast or too slowly, this may cause the medicine to not work as well.  It may also cause a side effect.

The TPMT gene gives instructions to your body to make a protein.  It is the job of the TPMT protein to break down certain medicines.  These medicines include thiopurines and are used in the treatment of cancer, inflammatory bowel disease, and other conditions.  Examples of these medicines are:

• Azathioprine
• Mercaptopurine
• Thioguanine

These are the medicines that we know of right now that are impacted by TPMT gene test results.  Medical experts keep finding new data about which medicines are affected by gene test results.

By testing your DNA, we can find DNA differences.  This can help us to see how well the proteins in your body work to break down certain medicines. 

The results of your TPMT gene test put you into 1 of 3 groups:

• Normal metabolizer: People in this group are likely to have normal working TPMT proteins.
• Intermediate metabolizer: People in this group may have reduced activity of TPMT proteins. 
• Poor metabolizer: People in this group may have very little or no active TPMT protein. 

 The results of this test can help your doctor choose the right medicine and dose for you.