Correct coding of any medical condition including diabetes mellitus is critical in determining the correct reimbursement for encounters related to this disease and for tracking the health care services provided. Providers of medical coding services have a clear understanding of the correct ICD-10-CM codes for diabetes mellitus that are combination codes that include the type of diabetes mellitus, the body system affected, and the complications affecting that body system.

According to the CDC’s National Diabetes Statistics Report for 2020, in 2018,

  • 34.2 million people, or 10.5% of the U.S. population had diabetes
  • 34.1 million adults aged 18 years or older of all US adults had diabetes
  • 10.2% of the population – had diagnosed diabetes, and
  • Approximately 7.3 million people have diabetes but have not yet been diagnosed

Coding diabetes mellitus first requires a clear understanding of this condition. There are two types of diabetes mellitus: Type I and Type II. In patients with type 1 diabetes, mainly in children, teens, and young adults, the pancreas doesn’t make enough or any insulin. At the same time, in type 2 diabetes, the cells in the patient’s body do not respond to insulin well, causing high blood sugar levels (hyperglycemia). For type 1 diabetes, insulin is delivered by injection or a pump to survive. In type 2 diabetes, blood glucose can be controlled with a healthy meal plan and a program of regular physical activity, losing excess weight, and taking medications.

Often, coders experience confusion in choosing the right codes for these diabetes types. Chronic hyperglycemia can come with the risk of serious health complications such as cardiovascular disease, kidney damage (nephropathy), foot damage, eye damage (retinopathy), nerve damage (neuropathy), hearing impairment, and depression. All these conditions need to be coded as well. Codes from categories E08 – E13 can be used to identify all the associated conditions that the patient has.

CMS Recommends These Diabetes Coding Best Practices

  • If the medical record does not specify the diabetes type, but indicates that the patient uses insulin, code it as
    • E11 Type 2 diabetes mellitus
    • Assign an additional code category Z79 helps to identify the long-term (current) use of insulin or oral hypoglycemic drugs.

    • Z79.4 Long term (current) use of insulin
    • Z79.84 Long term (current) use of oral hypoglycemic drugs

    Do not use the code Z79.4, if insulin is given temporarily to bring a type 2 patient’s blood sugar under control during an encounter.

  • To report pre-existing diabetes a pregnant woman has that complicates the pregnancy and gestational diabetes, assign a code from O24, followed by the appropriate diabetes codes. Use codes Z79.4 or Z79.84 if applicable.
    • O24 Diabetes mellitus in pregnancy, childbirth, and the puerperium
    • O24.0 Pre-existing type 1 diabetes mellitus, in pregnancy, childbirth and the puerperium
    • O24.1 Pre-existing type 2 diabetes mellitus, in pregnancy, childbirth and the puerperium
    • O24.3 Unspecified pre-existing diabetes mellitus in pregnancy, childbirth and the puerperium
    • O24.4 Gestational diabetes mellitus
    • O24.8 Other pre-existing diabetes mellitus in pregnancy, childbirth, and the puerperium
    • O24.9 Unspecified diabetes mellitus in pregnancy, childbirth and the puerperium
  • Avoid assigning any other codes from category O24 with the O24.4 subcategory codes.

  • Insulin pump malfunction complications can lead to underdose or overdose of insulin

    An underdose of insulin due to an insulin pump failure can be reported using code from subcategory T85.6 that specifies the type of pump malfunction, as the principal or first-listed code, followed by code T38.3X6.

    • T85.6, Mechanical complication of other specified internal and external prosthetic devices, implants and grafts
    • T38.3X6-, Underdosing of insulin and oral hypoglycemic [antidiabetic] drugs
  • Also, assign any additional codes for the type of diabetes mellitus and any associated complications due to the underdosing.

    Overdose of insulin due to insulin pump failure can be reported using code T85.6, followed by code T38.3X1.

    • T38.3X1 Poisoning by insulin and oral hypoglycemic [antidiabetic] drugs, accidental (unintentional)
  • Secondary diabetes is often caused by conditions or events such as cystic fibrosis, malignant neoplasm of pancreas, pancreatectomy, adverse effect of drug, or poisoning. Codes such as E08 (Diabetes mellitus due to underlying condition), E09 (Drug or chemical induced diabetes mellitus) and E13 (Other specified diabetes mellitus) can also help to report complications associated with secondary diabetes mellitus.

    For postpancreatectomy diabetes mellitus, use code E89.1. Assign a code from category E13 and a code from subcategory Z90.41 as additional codes.

    • E89.1 Postprocedural hypoinsulinemia
    • Z90.41 Acquired absence of pancreas

    If secondary diabetes is the result of Cushing’s syndrome, use code E24.9, followed by E08.9

    • E24.9 Cushing’s syndrome, unspecified
    • E08.9 Diabetes mellitus due to underlying condition without complications

    If the condition is caused by the adverse effects of steroids, report codes E09.9 and T38.0X5A.

    • E09.9 Drug or chemical induced diabetes without complications
    • T38.0X5A Adverse effect of glucocorticoids and synthetic analogues, initial encounter
  • Note that the word “with,” in Alphabetic Index refers to “associated with or due to”. In such cases, before assigning any linking codes check whether the provider specifically documents that the two conditions are related or unrelated. For instance, an AAPC blog notes that under E11.9 Diabetes/type 2/with, coders can find codes that describe
    • E11.44 Type 2 diabetes mellitus with diabetic amyotrophy
    • E11.618 Type 2 diabetes mellitus with other diabetic arthropathy
    • E11.43 Type 2 diabetes mellitus with diabetic autonomic (poly)neuropathy
    • E11.36 Type 2 diabetes mellitus with diabetic cataract
    • E11.610 Type 2 diabetes mellitus with diabetic neuropathic arthropathy
    • E11.22 Type 2 diabetes mellitus with diabetic chronic kidney disease etc.

To ensure appropriateness of codes and to accurately code the patient’s condition, coders must check the Tabular List in the Alphabetic Index and read parenthetical notes in the Index. To avoid coding errors, invest your time in reading provider documentation thoroughly and look for keywords to help determine the type of diabetes, complications and treatment regimen. Experienced medical coding outsourcing companies provide the services of skilled coders who can assign the correct diagnosis and procedure codes on the medical claims.