AIM: To investigate the efficacy of Sarcomeal® sachet, as a protein supplement, plus vitamin D3 on muscle parameters, metabolic factors, and quality of life (QoL) in individuals with diabetes and sarcopenia. METHODS: Sixty individuals were randomized into the control or intervention group. The intervention group received a daily dose of one Sarcomeal sachet and 1000 IU of vitamin D and both groups were recommended to consume protein-rich food, be educated about the disease, and perform physical activity for 12 weeks. Various assessments including muscle parameters, blood tests, and QoL were conducted at the beginning and the end of the trial. RESULTS: Over 12 weeks, although the intervention group had significant improvements in mean skeletal muscle mass index (SMI) (change: 0.17[0.016, 0.329] kg/m²
p <
0.05) and handgrip strength (change: 1.33[0.256, 2.410] kg
p <
0.05), differences between groups were not statistically significant. However, significant improvements were observed in lean mass (1.70 [0.749, 2.665] kg
P <
0.01) and lean mass index (0.62[0.287, 0.954] kg/m CONCLUSION: This mixture of supplements significantly improved lean muscle mass, preserved physical function, and helped maintain weight, supporting its potential as a strategy to counter muscle loss and enhance the QoL in diabetic sarcopenia patients. CLINICAL TRIAL REGISTRATION: This trial is registered at the Iranian Registry of Clinical Trials (IRCT) with IRCT20230831059311N1 ID.