Carbimazole warning sheet - Patient information sheet

Carbimazole information sheet for patients

You have been started on tablets to control your overactive thyroid gland. These tablets are very safe, but do occasionally cause the side effects of a rash or reduced blood cell count.

This sheet tells you what to do in the event of you experiencing symptoms which might indicate these effects. Please take the following action if you experience these symptoms while oneither carbimazole or propyl thiouracil (PTU) therapy:


If you develop a rash, please stop your medication and see your GP, bringing this letter with you. Your GP may prescribe you with an anti histamine drug to control the itching or rash if necessary. They may also switch you to an alternative drug to do the same job. The dose of propyl thiouracil is 10 times that of carbimazole, so if you are just taking 5mg of carbimazole, you will switch to 50mg of PTU.

Sore throat, fever, or mouth ulcers

If you develop any of these symptoms, please stop your medication immediately and bring this letter to hospital immediately to have a blood test. If possible, please let the endocrinology doctor on call know that you are coming, as this may speed things up for you. If this is not possible, please see your GP or go to the emergency department. Do not start taking your medication again until you have been told that your blood test is satisfactory.