Carbimazole: uses, side effects & brands

Written & medically reviewed by Dr. Sanjay Anbu, MBBS · Last reviewed 5 November 2026

Carbimazole is the main medicine for an overactive thyroid. It belongs to the Thyroid & hormone medicine group. These treat an overactive thyroid and some hormone-related conditions.

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Drug type — dosing is set by your doctor

Measure	Range
Drug class	Thyroid & hormone medicine
Type	Prescription
Dose	Individual — ask your doctor or pharmacist

What it is used for

Overactive thyroid (Graves' disease)
Overactive thyroid nodules (toxic nodular goitre)
Calming the thyroid before surgery or radioiodine
Used with levothyroxine in a "block and replace" plan

Common brand names

India: Neomercazole, Antithyrox
Worldwide: (carbimazole brands)

Common side effects

Nausea or mild stomach upset
Itchy rash
Joint aches
Headache or altered taste

Before taking it — precautions

Pregnancy — carbimazole can harm the baby, especially early in pregnancy; use reliable contraception and plan pregnancy with your doctor
Tell your doctor about liver disease or if you are breastfeeding
Regular blood tests are needed to adjust treatment

When to see a doctor urgently

Sore throat, mouth ulcers, fever or other signs of infection — stop and get a blood test the same day (urgent)
Yellow skin or eyes, dark urine or pale stools (urgent)
Severe rash, itching or swelling of the face

Not a prescription — no dose shown. The right dose of carbimazole depends on age, weight, kidney/liver function and the condition, so MedDroid does not show a dose here. Always get your dose from a doctor or pharmacist and the leaflet inside the pack. General educational information only.

Frequently asked questions

Why must I report a sore throat straight away?

Rarely, carbimazole can stop the body making white blood cells that fight infection. A quick blood test tells whether you need to stop it.

How soon will I feel better?

Symptoms usually start to improve after a few weeks. Treatment often continues for many months, guided by blood tests.

Can I get pregnant while taking carbimazole?

Plan it with your doctor first. Carbimazole has been linked to birth defects, so your doctor may switch you to another medicine before or during early pregnancy.

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Sources & further reading

Reviewed by Dr. Sanjay Anbu, MBBS. MedDroid is an AI medical assistant and can make mistakes. It provides general health information, not a diagnosis or medical advice — always consult a qualified clinician. In an emergency, contact your local emergency number immediately.