Side-effects due to Carbimazole occur most commonly during the first 2 months of treatment. They include nausea, vomiting, gastric distress, headache, arthralgia, skin rashes and pruritus. Bone-marrow depression has been reported and can lead to agranulocytosis. Patients should always be instructed to recognise symptoms which may suggest bone-marrow depression, to stop the drug and to seek immediate medical advice.