J Korean Diabetes.  2025 Mar;26(1):10-17. 10.4093/jkd.2025.26.1.10.

How Do We Diagnose Diabetes in Primary Care?

• Kim HJ

• KMID: 2567085
• DOI: http://doi.org/10.4093/jkd.2025.26.1.10

Abstract

Timely recognition of diabetes risk by primary care physicians facilitates appropriate interventions, reducing the risk of complications and improving quality of life in diabetics. Therefore, primary care physicians diagnosing diabetes must be aware of the advantages and disadvantages of various tests. Diabetes can be diagnosed by plasma blood glucose, glycated hemoglobin, or oral glucose tolerance testing. Since the fasting plasma blood glucose test has low sensitivity for diagnosing diabetes, it should be combined with glycated hemoglobin or oral glucose tolerance testing. In particular, in the case of glycated hemoglobin of 6.1% or more, fasting plasma glucose of 110~125 mg/dL, or with a risk factor for diabetes, the oral glucose tolerance test should be performed. The two important criteria that distinguish type 1 from type 2 diabetes are islet autoantibody status and C-peptide. If patients are autoantibody-positive or have a C-peptide level less than 0.6 ng/mL, a diagnosis of type 1 diabetes is suggested. Monogenic diabetes is likely among patients under the age of 35 (mainly under the age of 25) with one or more of the following features: A1C < 7.5% at diagnosis, one parent with diabetes, and features of a specific monogenic cause. In that case, primary care physicians should request a genetic test.

Keyword

Autoantibodies; Diagnosis; Glucose tolerance test; Glycated hemoglobin; Monogenic diabetes; Plasma blood glucose

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