BACKGROUND: Life expectancy among schizophrenic patients is 20% shorter than the general population. Currently, long-term use of antipsychotic drugs can induce metabolic symptoms, including weight gain, glucose intolerance, high blood glucose. AIM: This research aimed to investigate the fasting blood sugar level of a male patient with schizophrenia treated with flexible dose. METHODS: This research is an experimental study, unpaired numerical comparative analytic with non-probability consecutive sampling by recruiting 50 research subjects of men with male patients with schizophrenia. Every 25 people were treated with aripiprazole, and another 25 subjects were treated with risperidone. The flexible dose on how doses are equated with bioequivalent doses between aripiprazole and risperidone was applied. Sampling was carried out in the inpatient and outpatient clinic of the psychiatric hospital Prof. Dr M. Ildrem Medan, North Sumatra, Indonesia, in a span of 6 months from January 2018 to July 2018. The diagnostic test used a Mini structured interview system International Statistical Classification of Diseases-10 (Mini-ICD 10) and the statistical analysis was involving Mann Whitney U Test. RESULTS: This research showed the mean of fasting blood sugar level in week 8 in the group receiving treatment with aripiprazole was 88.96 with a standard deviation of 4.33 and in the group receiving risperidone treatment was 102.80 with a standard deviation of 2.92. The results of the analysis using unpaired t-test in the two groups showed a significant difference in fasting blood sugar levels for men with schizophrenia in the group receiving aripiprazole treatment and the group receiving risperidone treatment in week 8 with a value of p < 0.001 (p < 0.05). CONCLUSION: This research revealed that based on the equivalence of risperidone and aripiprazole dosage given to the male patients with schizophrenia, the treatment using risperidone can significantly increase the fasting blood sugar level compared to the aripiprazole treatment in week 8.