Methimazole Side Effects

Possible side effects of methimazole are listed below. Call your doctor for medical advice about side effects if they are severe or persist after a few days.

• Itchy skin rash
• Nausea, vomiting, upset stomach
• Hair loss
• Changes in taste
• Drowsiness
• Dizziness
• Muscle or joint pain
• Burning, prickling, tingling, tightness, pulling, or other abnormal sensations

Methimazole can also cause more serious symptoms. Call your doctor right away or seek emergency medical attention if you develop the following symptoms:

• Unusual or allergic reaction (signs and symptoms of allergic reactions include skin rash, hives, itching, swelling, or difficulty breathing)
• Unusual tiredness
• Fever, chills, sore throat, headache
• Decreased appetite, abdominal pain on the right side, yellowing of the skin or eyes
• Unusual bruising or bleeding

The above list may not include all the potential side effects of methimazole. Contact your healthcare provider if your side effects are unusual or severe or do not get better over time. You can also report unusual side effects to the Food and Drug Administration at 1-800-FDA-1088.

Methimazole Overdose: In case of an overdose of methimazole, call your doctor immediately. You can also call your local poison control center, provincial poison control center, or the national poison control center at 1-800-222-1222. Call 911 or emergency services if a person has collapsed, cannot breathe, has had a seizure, or cannot be awakened. 

Source: FDA