Q&A: ICD-10-CM coding for ‘Type 1.5’ diabetes mellitus

Q: A 14-year-old female patient was seen in the diabetes clinic for a follow-up visit. The provider documented "Combination Type 1 and Type 2, diabetes mellitus in poor control." The provider was queried and confirmed both Type 1 and Type 2 diabetes. This condition is sometimes called Type 1.5 diabetes. What is the correct ICD-10-CM code assignment for Type 1.5 diabetes?

A: Type 1.5 diabetes is a form of diabetes in which an adult has features of both Type 1 and Type 2 diabetes. These patients have also been described with the terms “latent autoimmune diabetes of adults” and “slow-progressing Type 1 diabetes.” The condition has also been called double diabetes, because individuals demonstrate both the autoimmune destruction of beta cells of Type 1 diabetes and the insulin-resistance characteristic of Type 2 diabetes.

Patients with Type 1.5 diabetes have autoantibodies to insulin-producing beta cells and gradually lose their insulin-producing capability, requiring insulin within 5–10 years of diagnosis, according to Coding Clinic, Third Quarter 2018, pp. 4–5.

To report Type 1.5 diabetes mellitus, coders should assign ICD-10-CM codes from category E13.- (other specified diabetes mellitus). In this case, the provider specifically documented “combination Type 1 and 2 diabetes mellitus in poor control”; therefore, the coder should assign code E13.65 (other specified diabetes mellitus with hyperglycemia).

Editor’s note: Sarah Humbert, RHIA, AHIMA-certified ICD-10-CM/PCS trainer, coding and compliance manager at KIWI-TEK LLC, and Temeka Davis, RHIT, coding manager at KIWI-TEK LLC, answered this question during HCPro’s webinar Simplify Complex ICD-10-CM Coding for Diabetes.

This answer was provided based on limited information. Be sure to review all documentation specific to your own individual scenario before determining appropriate code assignment.

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