Rybelsus is the first GLP-1 oral drug, improving the convenience of taking it for diabetic patients. Clinical studies have reported that a 14 mg oral dose of semalgutide is equivalent to a subcutaneous injection of 0.5 mg semalgutide and the presence of high concentrations of sodium N-[8-(2-hydroxybenzoyl)amino] caprylate (SNAC) has been shown to improve absorption of semalgutide. The formulation strategy to minimite the impact of dilution effects by SNAC is necessary, which can be achieved by targeting to stomach. However, semaglutide is a peptide drug, absorption through the stomach is limited by factors such as stomach enzymes and acidic pH. Analyzing the stability of semaglutide, the remaining amount of semaglutide at 120 min was 6.1%, 12.0%, and 73.7% at pH 1.2, pH 4.0, and pH 6.8. Additionally, it was confirmed that semaglutide had a solubility of 1 mg/mL at pH 6.8. As a additive to neutralize pH in stomach, four types of antacids (magnesium oxide (MgO), sodium bicarbonate, magnesium hydroxide, and calcium carbonate) were compared according to the amount of antacid at pH 1.5. MgO created an alkaline environment at a lower dose than other antacids, and other antacids required at least 1.3 to 3 folds amount of MgO. In future, the gastro-retentive tablet using MgO and low-density exicipients will be prepared and evaluated.