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Using this page · Individualise medicines monitoring

This medicines monitoring page has been written using publications and expert opinion. It is designed to save clinician time, but not replace professional responsibility. When using this page you should: ensure an individualised monitoring plan is developed in partnership with the patient and take account of any locally agreed advice and guidance.

Before starting


  • Baseline
    • Free T3
    • Free T4
    • Full blood countincluding white cell count (WCC)
    • Thyroid stimulating hormone
    • Liver function tests
    • White blood cell differential

Continued until stable


  • Every 6 weeks
    • Free T3continued until TSH in reference range
    • Free T4continued until TSH in reference range
    • Thyroid stimulating hormonecontinued until TSH in reference range


  • Periodically
    • Full blood countif clinical suspicion of agranulocytosis or liver dysfunction
    • Liver function testsif clinical suspicion of agranulocytosis or liver dysfunction

Ongoing once stable


  • Every 3 months
    • Thyroid stimulating hormone


  • Periodically
    • Free T3if TSH abnormal
    • Free T4if TSH abnormal
    • Creatine phosphokinaseif patient experiencing myalgia
    • Full blood countin patients who may be confused or have poor memory

Abnormal results

Hepatic function

If patient develops any signs and symptoms of hepatic disorder, temporarily stop carbimazole and perform LFTs immediately. Where liver function confirmed as abnormal, stop carbimazole.

White blood cells

If the patient develops any signs or symptoms of agranulocytosis or neutropenia, perform WBC count immediately, particularly where there is clinical evidence of infection.

Carbimazole should be stopped promptly upon clinical or laboratory evidence of neutropenia. Consider specialist referral for further management.


If acute pancreatitis occurs, carbimazole should be stopped immediately and permanently.

Thyroid function tests

Refer to endocrinologist if FT4 level falls below reference range or TSH is raised.


Advice to patients

Advise patients to be aware of the symptoms of low white blood cell count. Patients should stop the drug immediately and seek advice if they experience:

  • sore throat
  • bruising or bleeding
  • mouth ulcers
  • fever and malaise

Also advise women of childbearing potential to use effective contraception during treatment.

Discontinuation of carbimazole

For adults who have stopped carbimazole, consider measuring TSH (with cascading free T3 and free T4) within 8 weeks of stopping, then every 3 months for a year and then once a year.


Enquiries about this page

Contact us if you have any enquiries about the drug monitoring information on this page.