Think T1D in Adults Misclassified with T2D

Learn why T1D is often misclassified as T2D and how to differentiate the two in adults suspected of T1D .

Learning Objectives

Recognize the high rate of T1D misclassification in adults, understanding misclassification can lead to prolonged periods of inappropriate management and care
Identify clinical red flags that suggest T1D over T2D, such as unexpectedly deteriorating HbA1c despite treatment, rapid progression to insulin dependency, unexplained weight loss, or co-existing autoimmune diseases
Utilize appropriate diagnostic tools, combining clinical suspicion frameworks (like the AABBCC tool) with definitive islet autoantibody (IAb) to ensure correct diabetes classification

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Summary

Type 1 Diabetes (T1D) is a chronic, progressive autoimmune disease, yet up to 40% of adults with T1D are initially misclassified, mostly with T2D. This misclassification occurs because adults with T1D often present with "T2D features," such as older age, higher BMI (with ~50% being overweight or obese), and gradual onset. Correct classification is vital to avoid incorrect treatment, prevent prolonged insulin deficiency, reduce the risk of diabetic ketoacidosis, and offer treatments that delay progression. Primary care physicians should suspect T1D over T2D in patients showing unexpectedly deteriorating HbA1c, rapid progression to insulin, or unexplained weight loss. Suspicion can be guided by the AABBCC clinical tool and must be confirmed using islet autoantibody (IAb) testing.

MAT-GLB-2602347 - 0.1 - 10/2026.