We describe a case of a patient with Graves’ disease who failed to respond to carbimazole. Our patient remained thyrotoxic despite maximal carbimazole dosage. Our patient was switched to propylthiouracil which subsequently made the patient euthyroid. The patient was then definitively treated with radioiodine treatment. This case highlights the need to increase awareness of carbimazole resistance to prevent patients from being given escalating doses of carbimazole which increases the probability of adverse effects and extend their time in the hyperthyroid state.