ICD-10-CM guide
Type 2 Diabetes Coding with Insulin and Oral Medications: E11 and Z79
How to code type 2 diabetes in ICD-10-CM: pick the right E11 combination code, then add Z79.4, Z79.84, or Z79.85 for long-term medication use.
Reviewed 2026-09-29 | 2 min read
Diabetes coding looks simple until the chart mentions insulin, metformin, a kidney finding, and a high glucose reading in the same note. ICD-10-CM handles that with two layers. The E11 code describes the diabetes and its complications. The Z79 codes describe how the diabetes is being treated. Getting both layers right is the difference between a complete claim and a partial one.
Diabetes codes are combination codes
Each code in E08 to E13 carries the type of diabetes, the body system affected, and the complication in that system. Use as many codes from the category as needed to describe every documented complication, and sequence them by the reason for the encounter.
When no complication is documented, type 2 diabetes is E11.9, Type 2 diabetes mellitus without complications. When the provider documents hyperglycemia, E11.65 applies. When diabetic chronic kidney disease is documented, E11.22 applies, and the Tabular List instructs you to add the N18 code for the CKD stage.
Type 2 is the default
If the record does not state the type of diabetes, the default is E11. Insulin use does not change that default. A patient on insulin with no documented type is still coded to E11, with a Z79 code for the insulin.
Add a Z79 code for each drug class in long-term use
- Insulin: Z79.4, Long term (current) use of insulin.
- Oral hypoglycemic drugs such as metformin: Z79.84, Long term (current) use of oral hypoglycemic drugs.
- Injectable non-insulin antidiabetic drugs: Z79.85, Long-term (current) use of injectable non-insulin antidiabetic drugs.
- Two drug classes: report both Z79 codes. Insulin plus an oral agent is Z79.4 and Z79.84. Insulin plus an injectable non-insulin drug is Z79.4 and Z79.85. An oral agent plus an injectable non-insulin drug is Z79.84 and Z79.85.
Temporary insulin is not long-term use
Do not assign Z79.4 when insulin is given only to bring a type 2 patient's blood sugar under control during the encounter. Z79 codes describe continuous prescribed therapy, not a one-time dose.
Remission and resolved are not the same
E11.A, Type 2 diabetes mellitus without complications in remission, is assigned only when the provider documents remission. The guidelines note that resolved is not a synonym for remission. When the record is unclear, the provider should be queried.
A quick check before you finalize
- Is the type documented? If not, use E11.
- Does each documented complication have a matching E11 code, with any required additional code such as the CKD stage?
- Does each drug class in long-term use have its own Z79 code?
- Was any insulin only temporary during the visit? If so, leave Z79.4 off.
Questions coders ask
- Does insulin use mean the patient has type 1 diabetes?
- No. When the type is not documented and the patient uses insulin, the guidelines direct you to E11, Type 2 diabetes mellitus, plus Z79.4.
- What code do I use for type 2 diabetes on metformin?
- Assign the E11 code that matches the documented complications, or E11.9 when there are none, and add Z79.84 for the long-term oral hypoglycemic drug.
- Can I report Z79.4 and Z79.84 together?
- Yes. When a patient is treated with both insulin and an oral hypoglycemic drug, both codes should be assigned.
- Should Z79.4 be used when insulin is given once in the office?
- No. Insulin given temporarily to control blood sugar during an encounter is not long-term use.
Practice these rules
Sources
ICD-10-CM Official Guidelines for Coding and Reporting FY 2027
Section I.C.4.a, Diabetes mellitus
ICD-10-CM Official Guidelines for Coding and Reporting FY 2027
Section I.C.4.a.1.b, Type 2 diabetes mellitus in remission
ICD-10-CM Official Guidelines for Coding and Reporting FY 2027
Section I.C.4.a.2, Type of diabetes mellitus not documented
ICD-10-CM Official Guidelines for Coding and Reporting FY 2027
Section I.C.4.a.3, Diabetes mellitus and the use of insulin, oral hypoglycemics, and injectable non-insulin drugs
ICD-10-CM Official Guidelines for Coding and Reporting FY 2027
Section I.C.21.c.3, Status, category Z79
FY 2027 ICD-10-CM Code Descriptions in Tabular Order
Codes E11.9, E11.22, E11.65, E11.A, Z79.4, Z79.84, Z79.85