 Recently published European guidance recommends the evaluation of the radiation dose to the bone marrow in patients undergoing radioiodine therapy for thyroid cancer. The methods described in these guidelines require serial blood samples to be taken from the patient, followed by a sophisticated analysis to determine the radiation dose. However, radiation risk assessments carried out locally have indicated that a relatively high radiation exposure will be received by the operator taking the blood samples, which may prohibit this procedure being carried out routinely. 