The Royal College of Physicians guidelines (2007) on follow-up post radioiodine therapy for hyperthyroidism recommend thyroid function monitoring around weeks 6, 12, 26, 39, 52 and yearly thereafter in stable patients. We retrospectively analyzed data from 91 patients given radioiodine in 2005 who were followed-up locally comparing our practice with these standards. Fifteen percent of patients were lost to follow-up before year one with 40% of these not having their thyroid function normalized at their last check-up. The rest were monitored for 2 years minimum. Sixty-one percent met the blood targets in the first 6 months with only 47% meeting the requirements between six and twelve months and 83% compliance thereafter.69% of patients developed either transient or permanent hypothyroidism. 24% of patients hit hypothyroidism by the end of 3 months, 50% by the end of 6 months, 63% within12 months. The highest incidence (17%) of hypothyroidism was between weeks 12 and 16. Striking was the speed and severity in which hypothyroidism developed. In the first 4 weeks 5.5% of patients went hypothyroid, 20% of these with TSH>40 at initial presentation. By the end of 8 weeks, 15% of patients were hypothyroid and 40% of these had TSH>40. Hyperthyroidism did not settle with one dose or recurred in 21% of patients with the highest incidence of recurrence (8.1%) 3 to 6 months following radioiodine. Thyroid function tests never normalized on follow-up of 20% patients. At the end of year one (or two respectively), 19% (18%) remained euthyroid, 16% (12%) hyperthyroid, 9% (3%) clinically hypothyroid and 42% (49%) were hypothyroid on adequate replacement. Our findings stress the importance of an early and frequent screening. Resources have been put in place to set up a telephone clinic to allow for tighter monitoring in order to improve upon our practice.