There are two dosing methods for radioiodine dose administration including empirical fixed dose and calculated dose. Recent meta-analysis supported that dose calculation is better than empirical fixed dose. However, dose calculation by dosimetry or 24 hours radioiodine uptake ratio can be tedious. Pertechnetate thyroid scintigraphy is a simple nuclear imaging that can be completed on the same day and pertechnetate thyroid uptake ratio determined from the scintigraphy can be used to calculate the radioiodine dose. This research is done to measure the efficacy of the calculated dose regime. Methods: Hyperthyroidism patients referred for first radioiodine therapy were recruited. Pertechnetate thyroid scintigraphy was done and pertechnetate uptake ratio used for dose calculation. The outcome of the treatment was determined at six months. Results: A total of 95 patients were recruited. Six months after treatment, 82.1% of the calculated dose cohort achieved euthyroid or hypothyroid state. Participants with multinodular goitre had higher failure rate than those with Graves’ disease (p=0.032) although there was no difference in the median RAI dose given (p=0.866). Conclusion: This calculated dose method showed good outcome with 82.1% cure rate at six months post treatment.