Decreased organ function in geriatric patients can lead to several disorders such as diabetes mellitus. This occurs due to decreased sensitivity of organ function which causes potential side effects such as hypoglycemia. This study aimed to evaluate effectiveness use of antidiabetic in reduce blood sugar in geriatric population. This study is a prospective descriptive observational study with a cross sectional method. The sample was purposively sampled from geriatric outpatient clinic and the Medical Records department of Dr Moewardi Surakarta Hospital. The collected data were analyzed univariately to compare patient characteristics and the effectiveness of antidiabetic medication used. This study found that female patients were most frequently affected by diabetes mellitus, with the highest prevalence observed in the age group of 70-79 years and among those with a history of drug use of least 2 years. Metformin + Insulin Humalog is an antidiabetic drug with the antidiabetic medicines that have the most significant amount of blood sugar reduction,while the most effective antidiabetic to achieve the therapeutic target of reducing blood sugar levels in geriatric patients is metformin + Insulin Ryzodeg. This study concludes that a combination of antidiabetics and insulin is the most effective antidiabetic for achieving the therapeutic target of lowering blood sugar levels in geriatric patients at Dr. Moewardi Surakarta Hospital.