Purpose: The aim of this study was to determine the influence of H2RAs to the 24-h I-131 uptake in the thyroid gland.Material and Methods A prospective study with quasi-experimental pre- and post-study design was done. Subjects with normal fT4 level who fulfilled the inclusion criteria were selected. All subjects received 0.2 mCi of I-131 orally, and the thyroid uptake calculations were performed at 24 h later. The same procedure was performed 4 weeks later. All of the subjects were asked to consume H2RAs 1 h before the administration of I-131 of the second procedure. Both 24-h thyroid uptakes were statistically analysed. Results: A total of 14 subjects were enrolled in this study. Most of them were women (78%) with an average age of 37.6 years old (range: 20–55). This study showed a median of 24-h thyroid uptake of I-131 before and after H2-receptor antagonist of 20.6% (range: 11.1–57.8%) and 16.7% (range: 8.1–39.4%) respectively. Conclusion H2-receptor antagonist caused a significance reduction of 24-h I-131 uptake value in the thyroid gland.