Carbimazole and PTU information

You have been started on tablets to control your overactive thyroid gland.

These tablets are very safe, but very rarely may cause well-recognised side effects of rash or reduced blood cell count.

This sheet tells you what to do in the event of you experiencing symptoms indicating such effects.

You should take the following action if you experience these symptoms while on this drug therapy:


a. Stop medication

b. Consult your gp and give them this letter


a. Stop medication

b. Attend hospital immediately and have blood count checked

c. The Endocrinology registrar should be contacted during working hours.

Information for GP's

This patient is on carbimazole / PTU and has developed a rash. If on carbimazole please could you prescribe propylthiouracil (PTU) in place of the carbimazole?

The dose of PTU is 10 times the dose of carbimazole (e.g. 30mg of carbimazole = 300mg PTU) and should be given two to three times per day.

If the patient has had both carbimazole and PTU, or you are concerned about the patient or require further information, please contact the endocrine registrar during working hours via switchboard.

If the patient attends with symptoms suggestive of neutropenia please check an urgent blood count and contact the endocrine team immediately.

Thank you for your help.

Printable patient information