Propylthiouracil (PTU): uses, side effects & brands

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

PTU treats overactive thyroid and is preferred in early pregnancy. 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 in the first three months of pregnancy
Thyroid storm (a severe emergency, in hospital)
Overactive thyroid when methimazole or carbimazole cannot be used

Common brand names

India: PTU, Thyrocil
Worldwide: (propylthiouracil brands)

Common side effects

Nausea or stomach upset
Itchy rash
Joint aches
Altered taste

Before taking it — precautions

PTU can cause serious liver damage, so it is usually a second choice — tell your doctor about any liver disease
After early pregnancy your doctor will usually switch you to methimazole or carbimazole
Regular blood tests are needed to check thyroid levels

When to see a doctor urgently

Yellow skin or eyes, dark urine, pale stools, loss of appetite or pain in the upper right belly (urgent)
Sore throat, mouth ulcers or fever — stop and get a blood test the same day (urgent)
Severe rash, painful swollen joints or blood in urine

Not a prescription — no dose shown. The right dose of propylthiouracil 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 is PTU used in early pregnancy?

Methimazole and carbimazole have been linked to birth defects when taken in the first three months, so PTU is often preferred during that time.

Why is PTU not used for everyone?

It carries a higher risk of serious liver injury than methimazole, so it is kept for specific situations.

What should I watch for?

Signs of liver trouble (yellow eyes, dark urine, tummy pain) and signs of infection (sore throat, fever). Report either straight away.

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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.