a. Diabetes mellitus

The diabetes mellitus codes are combination codes that include the type of diabetes mellitus, the body system affected, and the complications affecting that body system. As many codes within a particular category as are necessary to describe all of the complications of the disease may be used. They should be sequenced based on the reason for a particular encounter. Assign as many codes from categories E08 - E13 as needed to identify all of the associated conditions that the patient has.

1) Type of diabetes

The age of a patient is not the sole determining factor, though most type 1 diabetics develop the condition before reaching puberty. For this reason type 1 diabetes mellitus is also referred to as juvenile diabetes.

2) Type of diabetes mellitus not documented

If the type of diabetes mellitus is not documented in the medical record the default is E11.-, Type 2 diabetes mellitus.

3) Diabetes mellitus and the use of insulin and oral hypoglycemics

If the documentation in a medical record does not indicate the type of diabetes but does indicate that the patient uses insulin, code E11-, Type 2 diabetes mellitus, should be assigned. Additional code(s) should be assigned from category Z79 to identify the long-term (current) use of insulin, oral hypoglycemic drugs, or injectable non-insulin antidiabetic, as follows:

If the patient is treated with both hypoglycemic drugs and insulin, both code Z79.4, Long term (current) use of insulin, and code Z79.84, Long term (current) use of oral hypoglycemic drugs, should be assigned.

If the patient is treated with both insulin and an injectable non-insulin antidiabetic drug, assign codes Z79.4, Long term (current) use of insulin, and Z79.85, Long-term (current) use of injectable non-insulin antidiabetic drugs.

If the patient is treated with both oral hypoglycemic drugs and an injectable non-insulin antidiabetic drug, assign codes Z79.84, Long term (current) use of oral hypoglycemic drugs, and Z79.899, Other long term (current) drug therapy.

Code Z79.4 should not be assigned if insulin is given temporarily to bring a type 2 patient’s blood sugar under control during an encounter.

4) Diabetes mellitus in pregnancy and gestational diabetes

See Section I.C.15. Diabetes mellitus in pregnancy. See Section I.C.15. Gestational (pregnancy induced) diabetes

5) Complications due to insulin pump malfunction

(a) Underdose of insulin due to insulin pump failure
An underdose of insulin due to an insulin pump failure should be assigned to a code from subcategory T85.6, Mechanical complication of other specified internal and external prosthetic devices, implants and grafts, that specifies the type of pump malfunction, as the principal or first-listed code, followed by code T38.3X6-, Underdosing of insulin and oral hypoglycemic [antidiabetic] drugs. Additional codes for the type of diabetes mellitus and any associated complications due to the underdosing should also be assigned.

(b) Overdose of insulin due to insulin pump failure
The principal or first-listed code for an encounter due to an insulin pump malfunction resulting in an overdose of insulin, should also be T85.6-, Mechanical complication of other specified internal and external prosthetic devices, implants and grafts, followed by code T38.3X1-, Poisoning by insulin and oral hypoglycemic [antidiabetic] drugs, accidental (unintentional).

6) Secondary diabetes mellitus

Codes under categories E08, Diabetes mellitus due to underlying condition, E09, Drug or chemical induced diabetes mellitus, and E13, Other specified diabetes mellitus, identify complications/manifestations associated with secondary diabetes mellitus. Secondary diabetes is always caused by another condition or event (e.g., cystic fibrosis, malignant neoplasm of pancreas, pancreatectomy, adverse effect of drug, or poisoning).

(a) Secondary diabetes mellitus and the use of insulin, oral hypoglycemic drugs, or injectable non-insulin drugs
For patients with secondary diabetes mellitus who routinely use insulin, oral hypoglycemic drugs, or injectable non-insulin drugs, additional code(s) from category Z79Z79 should be assigned to identify the long-term (current) use of insulin, oral hypoglycemic drugs, or non-injectable non-insulin drugs as follows:

If the patient is treated with both oral hypoglycemic drugs and insulin, both code Z79.4, Long term (current) use of insulin, and code Z79.84, Long term (current) use of oral hypoglycemic drugs, should be assigned.

If the patient is treated with both insulin and an injectable non- insulin antidiabetic drug, assign codes Z79.4, Long- term (current) use of insulin, and Z79.85, Long-term (current) use of injectable non-insulin antidiabetic drugs.

If the patient is treated with both oral hypoglycemic drugs and an injectable non-insulin antidiabetic drug, assign codes Z79.84, Long-term (current) use of oral hypoglycemic drugs, and Z79.85, Long-term (current) use of injectable non-insulin antidiabetic drugs.

Code Z79.4 should not be assigned if insulin is given temporarily to bring a secondary diabetic patient’s blood sugar under control during an encounter.

(b) Assigning and sequencing secondary diabetes codes and its causes
The sequencing of the secondary diabetes codes in relationship to codes for the cause of the diabetes is based on the Tabular List instructions for categories E08, E09 and E13.

(i) Secondary diabetes mellitus due to pancreatectomy
For postpancreatectomy diabetes mellitus (lack of insulin due to the surgical removal of all or part of the pancreas), assign code E89.1, Postprocedural hypoinsulinemia. Assign a code from category E13 and a code from subcategory Z90.41-, Acquired absence of pancreas, as additional codes.

(ii) Secondary diabetes due to drugs
Secondary diabetes may be caused by an adverse effect of correctly administered medications, poisoning or sequela of poisoning.

See section I.C.19.e for coding of adverse effects and poisoning, and section I.C.20 for external cause code reporting.