Looking for something?

Find it in our extensive resource library!

Smart Filters

  • Reset
  • Services

  • Who it's for

  • What it’s about

  • Format

View: 90

Download: 8


This resource explains the potential side effects your child could experience as a result of taking anti-thyroid medication (Carbimazole). If you have any questions or concerns, please contact the endocrinology team.

Your child’s consultant is:


This is an anti-thyroid drug, taken by patients with an overactive thyroid (hyperthyroidism or Grave’s disease). This drug reduces the amount of thyroid hormone in the body.

Carbimazole is available as tablets, that may be swallowed whole or crushed and mixed with water.

What to do if you miss a dose

If you have forgotten to give your child a dose, you can give them the missed dose, if it is more than 12 hours before the next dose is due. Then give the following dose as normal at the usual time.

If it is less than 12 hours until the next dose is due, simply give your child their next dose at the usual time, accepting that they will have missed a dose.

Carbimazole and pregnancy

Carbimazole can harm an unborn baby whilst in a mother’s womb. This is a particular concern if a mother is taking carbimazole during the first trimester of pregnancy (first 3 months).

Young women of child-bearing potential (those who have started their periods), should speak to their doctor if they think there is any chance of becoming pregnant and use effective contraceptive whilst being treated with carbimazole.


If you think you may be pregnant, you should contact your doctor immediately.

Important side effects

A rare, but serious, side effect of Carbimazole is that it can cause a reduction of white blood cell number. If that number drops too low, it is called ‘agranulocytosis’ and puts the child at risk of serious infection.

Symptoms of agranulocytosis

If your child experiences any of the following symptoms:

  • sore throat
  • fever of above 37.5 degrees Celsius
  • mouth ulcers

Then they must:

  • stop taking Carbimazole
  • attend a general practice (GP) or emergency department the same day for a blood test for a full blood count

Present this to the doctor or healthcare professional:

Risk of bone marrow supression
This patient is taking Carbimazole for hyperthyroidism. A rare, but serious, potential side effect of this treatment is agranulocytosis. If they are experiencing signs or symptoms of infection, then a full blood count is required. These symptoms include:
  • Fever
  • Sore Throat
  • Mouth Ulcers

If these, or any other concerns of infection, are present the patient should stop taking Carbimazole, and the following should be done:

  • Take a Full Blood Count
    • If the Absolute Neutrophil Count is greater than 2 x 109 per litre, then Carbimazole may be restarted, and the patient reassured.
    • If the Absolute Neutrophil Count is less than 2 x 109 per litre, then discuss the patient with the medical or haematology registrar on-call, and make sure the endocrinology team are informed.

Contact us

If you have any questions or concerns, please contact the endocrinology secretaries on 0114 271 7000.

If you are concerned about your child’s health, ask to speak to the endocrinology nurses or registrar (or the medical registrar on-call if out of hours).

Is something missing from this resource that you think should be included? Please let us know

Contact us


Please note this is a generic information sheet relating to care at Sheffield Children’s. The details in this resource may not necessarily reflect treatment at other hospitals. This information is not intended as a substitute for professional medical care. Always follow your healthcare professionals’ instructions. If this resource relates to medicines, please read it alongside the medicine manufacturer’s patient information leaflet. If you have specific questions about how this resource relates to your child, please ask your doctor.

Resource number: END19

Resource Type: Article

How useful did you find this resource?*


Western Bank
S10 2TH

United Kingdom

Switchboard: 0114 271 7000

Interesting Facts

We’ve got a special MRI scanner just for teddies so children can see what it’s like before they have a scan.

Help to transform our extraordinary hospital into something even better.

Sheffield Children's@SheffChildrens
As a result of Mia donating her organs, five people received life saving transplants. Marie said: “Mia’s death has… https://t.co/RwsWVcXdO6

As of 6 July 2022 everyone (colleagues, patients and families) must wear a mask. This applies to all spaces across. all sitesMore information on how we are keeping you safe is available here.

By continuing to use the site, you agree to the use of cookies. more information

The cookie settings on this website are set to "allow cookies" to give you the best browsing experience possible. If you continue to use this website without changing your cookie settings or you click "Accept" below then you are consenting to this.