Diabetes mellitus, commonly known as diabetes, is a metabolic disease characterized by high blood sugar levels that result from defects in insulin secretion or its action or both.

Normally the blood glucose levels are controlled by insulin, a hormone produced by the pancreas. The primary function of insulin is to normalize the glucose level by promoting the uptake of glucose into body cells. When the function of insulin is disrupted, blood glucose level is elevated resulting in diabetes. The two mechanisms that would results in diabetes are as follows:

1. Inadequate production of insulin.

2. Inadequate sensitivity of cells to the action of insulin.

Based on the above mechanisms, the diabetes can be classified into two main types as

1. Type 1 diabetes ( insulin dependent diabetes)

2. Type 2 diabetes (non-insulin dependent diabetes)

Type 1 diabetes:

In type 1 diabetes, the immune system attacks the pancreatic beta cells so that they no longer produce insulin. According to CDC, around 5 percent of people with diabetes have type 1.

Type 2 diabetes:

In type 2 diabetes, the pancreas produces insulin, but the body’s cells start to resist the effects of insulin. This means glucose cannot enter the cells. Instead, it builds up in the blood thereby elevating the blood glucose level.

In ICD-10 CM, diabetes is classified in categories E08-E13 listed as below:

  • E08 Diabetes Mellitus due to an underlying condition
  • E09 Drug or chemical induced diabetes mellitus
  • E10 Type I diabetes mellitus
  • E11 Type 2 diabetes mellitus
  • E13 Other specified diabetes mellitus

The diabetes mellitus codes are combination codes that include the:

  • Type of diabetes mellitus
  • The body system affected
  • Complications affecting the body system.

Example: E10.311 Type 1 diabetes mellitus with unspecified diabetic retinopathy with macular edema.

Coding tip for Type 1 diabetes:

  • Category E10 denotes Type 1 diabetes mellitus.
  • Type 1 diabetes mellitus (category E10) can also be described as ketosis-prone, juvenile onset, idiopathic diabetes or brittle diabetes.
  • Type 1 diabetics must use insulin because their pancreas does not produce insulin naturally. Therefore, it is not necessary to assign code Z79.4 (Long term (current) use of insulin) for type 1 DM cases.

Coding tip for Type 2 diabetes:

  • Category E11 denotes Type 2 diabetes mellitus.
  • Type 2 DM may also be described as insulin-resistant.
  • Use additional code to identify any insulin use. (Z79.84)
  • If the patient is treated with both oral medications and insulin, only the code for insulin should be assigned.

Default type:

When the type of diabetes mellitus is not documented in the medical record, the default code is E11 – Type 2 diabetes mellitus.

Use of insulin and oral hypoglycemics:

Code Z79.4 should be assigned for the type 2 diabetes mellitus if the medical record indicates that the patient uses insulin.

Code Z79.4 should not be assigned if insulin is given temporarily to bring a type 2 patient’s blood sugar under control or for type 1 diabetes mellitus.

Complications due to insulin pump malfunction:

Failure or malfunction of the pump may result in under dosing or overdosing of insulin. Both of these situations are considered to be mechanical complications and are assigned a code from subcategory T85.6 mechanical complication of other specified internal and external prosthetic devices, implants and grafts. The appropriate T85.6- code is selected depending on the type of malfunction as the following:

T85.614 Breakdown (mechanical) of insulin pump

T85.624 Displacement of insulin pump

T85.633 Leakage of insulin pump

In addition, codes are assigned to specify underdose (T38.3×6-) or overdose (T38.3×1-) as well as the code for the type of diabetes mellitus and any associated complications

Table: Coding for Underdose/overdose of insulin due to insulin pump failure.

Secondary Diabetes mellitus:

Secondary diabetes is defined as the diabetes that results from another medical condition or due to the treatment of a medical condition that causes abnormal blood glucose levels.

Causes of secondary DM:

Pancreatic disease: cystic fibrosis, chronic pancreatitis, pancreatectomy, carcinoma of pancreas.

Endocrine: cushing’s syndrome, acromegaly, thyrotoxicosis, phaeochromocytoma, glucagonoma.

Drug-induced: thiazide diuretics, corticosteroids, atypical antipsychotics, antiretroviral protease inhibitors.

Code categories:

E08: Diabetes mellitus due to underlying condition

E09: Drug or chemical induced diabetes mellitus

E13: Other specified diabetes mellitus (postpancreatectomy diabetes mellitus)

Secondary Diabetes mellitus due to underlying condition:

  • Secondary diabetes due to an underlying condition is coded to category E08 with the underlying condition coded first.
  • Underlying conditions include congenital rubella (P35.0), Cushing’s syndrome (E24.), cystic fibrosis (E84.-), malignant neoplasm (C00- C96), malnutrition (E40-E46), and pancreatitis and other diseases of the pancreas (K85-, K86.-).

Secondary Diabetes mellitus due to drugs or chemical induced:

  • Secondary diabetes drug-induced or chemically induced is coded to category E09.
  • For example, steroid-induced diabetes mellitus due to prolonged use of prednisone for an unrelated condition is coded as E09.9 drug or chemical induced diabetes mellitus without complications followed by code T38.0X5- adverse effect of glucocorticoids and synthetic analogs.

Secondary Diabetes mellitus due to pancreatectomy:

  • Secondary diabetes mellitus due to pancreatectomy is coded to E89.1, postprocedural hypoinsulinemia.
  • A code from category E13 should also be assigned.
  • Either code Z90.410 acquired total absence of pancreas or code Z90.411 acquired partial absence of pancreas are coded as additional diagnoses.

Causal relationship between diabetes and other conditions:

The ICD-10-CM presumes a causal relationship between two conditions when they are linked with the terms “with” or “in.” These terms should be interpreted to mean “associated with” or “due to” when they appear in a code title, the Alphabetic Index or an instructional note in the tabular list.1. Based on this guideline, there is a presumed causal relationship between diabetes and those conditions listed under “with”.

Example: ICD-10-CM presumes a causal relationship between diabetes and cataracts. Diabetes and cataracts should be coded as related even when the provider is not specifically linking them, unless the documentation clearly states that the conditions are not related.

From the above screenshot, you can see the other conditions linked with the terms “with” under diabetes. Therefore even when the provider does not specifically links both the diabetes and other conditions, you are allowed to code both the conditions as related unless the documentation clearly states that the conditions are unrelated.

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