Explanation

A TMPT test is when you have a blood test to see if your body makes an enzyme called thiopurine s-methyltransferase. Not all people make this enzyme - it depends on your gene whether you do or don't.

Why do I need a TPMT test?

If you don't have any or very much of this enzyme you may be too sensitive to a type of medicines called thiopurines, like azathioprine. This means you will get much worse side effects if you take these medicines. If your doctor is thinking of treating you with thiopurines, he or she may ask you to do a TMPT test.

Also, if you're already taking a thiopurine medicine and you're having bad side effects your doctor can do a TPMT test to check if you get these side effects because you don't have enough TPMT enzyme.

What happens before I have a TPMT test?

You don't need to do any special preparation for a TPMT test, just turn up on time.

How is the TPMT test done?

A blood test will be done on the inside of your elbow or possibly on your wrist or the back of your hand.

The doctor or nurse will clean your skin over the vein and then put a needle in. When the doctor or nurse has got your blood sample the needle will be taken out and it's all over.

Will the TMPT test hurt?

You will just feel a tiny prick when the needle goes in, but it shouldn't hurt very much. If you do not like needles and injections, tell the person who is taking the sample, so that they can help you to relax. If you feel like you are going to faint, you should tell the person doing your test and they will get you to lie down until you feel better.

What happens after the TMPT test?

Your blood sample is sent to a laboratory to measure your TMPT levels. The results will be given to your doctor and he or she will explain to you what they mean.

So that you don't get really bad side effects, your doctor may change your medicine or the dose depending on your TMPT test results.

What if I have any other questions about TMPT test?

If you have any other questions, you can ask your doctor, or chat to other people about TMPT or blood tests in the Medikidz forums and virtual world, Mediland.