It is said that diabetes is one of the factors contributing to the onset of dementia and accelerating its progression. The number of dementia cases is expected to increase steadily year by year. Such being the circumstances, we encountered an elderly woman with diabetes and dementia, who managed to lower her blood glucose values to a proper level somehow or other, thus lightening the burden of caregivers. We shall hereby report the case because we thought it would make a good example for care in the region where the population is rapidly graying. The woman, then at age 80, visited our hospital complaining of languidness. Her blood sugar level was so high (random blood glucose level: 1,096 mg/dl) that she was hospitalized at once. By a stepwise insulin reinforcement therapy, the blood glucose levels were under control. During the stay in hospital, she was also diagnosed as having senile dementia. She was provided with effective health care and education for the control of blood sugar levels. Having snacks between meals was strictly prohibited. Considering that she was an elderly person living alone, only internal medicines were given. As a result, her blood glucose levels were elevated to about 300 mg/dl, but the combined use of GLP-1 injection and internal medicine once a week had good control over blood glucose levels. So, the patient was discharged from the hospital.