Diabetes ICD-10 Codes: E10, E11, O24 and Z79 Rules (FY2027)

By Awais Afzal, Healthcare Operations & Data Analyst · Published February 23, 2026 · Updated October 14, 2026

Diabetes ICD-10 codes sit in categories E08 to E13: E10 for type 1, E11 for type 2, O24.4- for gestational diabetes. If the type is not documented, the guidelines default to E11. Add a Z79 code for insulin, oral or injectable drugs. This guide uses the FY2027 code set.

A chart says “diabetes,” and a coder has to turn that into one or several codes. The right answer depends on the documented type, each complication and the drugs the patient takes. The old habit of stopping at E11.9 hides most of that.

This guide is for coders, billers and practice managers. It covers the common E10 and E11 codes, the Z79 codes, remission, secondary and gestational diabetes, and the checks that catch errors before submission. It is not clinical advice, and the provider’s documentation always controls the code.

How diabetes ICD-10 codes are built

Diabetes codes live in categories E08 to E13, and the guidelines call them combination codes. The FY2027 ICD-10-CM Official Guidelines say to assign as many codes from E08 to E13 as needed to capture every diabetes-related condition, then sequence them by the reason for the encounter. The type of diabetes picks the category. The documented complications pick the characters after the decimal point.

In practice, the coding question is rarely “which diabetes code?” It is “what did the provider document?” The sections below follow the same order a coder uses: type first, then complications, then the drug-use codes, then the special cases.

What if the note does not say the type?

Default to type 2. The FY2027 guidelines state that when the type is not documented, the coder assigns a code from E11. Age alone does not decide the type, and the guidelines note that type 1 is also called juvenile diabetes. If the provider has documented the type, that wording wins over any assumption about the patient.

Which code set applies?

The FY2027 code set applies to encounters from October 1, 2026 through September 30, 2027, according to the CMS ICD-10 page. The code set changes each October, so always match the code to the date of service.

Type 2 diabetes codes (E11) you will see most

E11 is the category for type 2 diabetes, and it is the one that applies when the type is not stated. The E11 Tabular entry includes diabetes NOS and insulin-resistant diabetes, and it carries a note to use an additional code to identify control with insulin (Z79.4), oral drugs (Z79.84) or injectable non-insulin drugs (Z79.85). Titles below come from a FY2027 E11 listing and are written here in plain words.

Source: FY2027 E11 listing on icdlist.com (secondary mirror of the CMS FY2027 ICD-10-CM dataset); E11.319, E11.649 and E11.621 titles from the Qwick Coder / CWC Diabetes ICD-10 sheet (2017). Confirm in the official Tabular List.

Hyperglycemia, hypoglycemia and the word "uncontrolled"

A common denial trigger is a code that claims more than the note supports. A provider writing “uncontrolled diabetes” has not told the coder whether the patient is hyperglycemic or hypoglycemic. E11.65 reports hyperglycemia and E11.649 reports hypoglycemia without coma, so the note has to say which one. When it does not, the safest step is a query to the provider, not a guess.

When E11.9 is the right code

E11.9 is correct when the provider documents type 2 diabetes and no complication. It becomes a problem when the same chart documents a complication elsewhere, such as an eye exam finding or a foot ulcer, and the claim still goes out with E11.9. A reviewer comparing the diagnosis to the chart sees the mismatch. Sampling E11.9 claims against the notes is a simple first audit.

For the foot-care side of these claims, see our guide to routine foot care billing and coding. For supplies, see Medicare coverage of diabetic supplies.

Type 1 diabetes codes (E10)

E10 mirrors E11 for most complications. The E10 category includes juvenile-onset diabetes, brittle diabetes and diabetes due to an autoimmune process, according to the FY2027 E10 listing. It is not billable on its own, so the claim needs a more specific code.

Source: FY2027 E10 listing on icdlist.com (secondary mirror of the CMS FY2027 dataset); presymptomatic guidance from the FY2027 ICD-10-CM Official Guidelines, section I.C.4.a.

Never report E10 and E11 together for the same patient unless the conditions are truly unrelated. Each category lists the other under Excludes1. When the chart is unclear, a provider query is the fix.

Z79 codes: reporting insulin, oral and injectable drugs

Z79 codes tell the payer how the patient’s diabetes is being treated long term. The guidelines name three: Z79.4 for long-term current insulin use, Z79.84 for long-term current oral hypoglycemic drugs, and Z79.85 for long-term current injectable non-insulin antidiabetic drugs.

The old advice to “mention insulin use” is too loose. The Z79 code is a reported code, not a free-text comment, and which one applies depends on the drug class in the medication list. A chart with insulin and metformin needs two Z79 codes, not one.

Remission, secondary diabetes, pumps and gestational diabetes

Some charts do not fit the standard E10 or E11 pattern. The category depends on what caused the diabetes or when it occurs.

Source: FY2027 ICD-10-CM Official Guidelines for Coding and Reporting, sections I.C.4.a and I.C.15 cross-reference (CDC/NCHS, effective October 1, 2026); Excludes1 lists from the FY2027 E10 and E11 listings.

Gestational diabetes (O24.4-)

Gestational diabetes sits in the pregnancy chapter, not in E10 or E11. In a FY2027 listing, O24.410 is gestational diabetes in pregnancy, diet controlled; O24.414 is insulin controlled; O24.415 is controlled by oral hypoglycemic drugs; and O24.419 is unspecified control (FY2027 O24 listing). “Unspecified control” means the note did not state how it was managed. It does not mean the diabetes was uncontrolled.

For the puerperium codes and the Z79 rules in pregnancy, use the guideline section I.C.15 and the Tabular List directly. Those pages were not verified for this article.

Why diabetes coding gets so much attention

Diabetes is common and costly. The CDC’s National Diabetes Statistics Report page lists 40.1 million people in the US with diagnosed or undiagnosed diabetes, or 12.0% of the population, using 2023 data (CDC). The American Diabetes Association estimated the total cost of diabetes in the US at $412.9 billion in 2022, including $306.6 billion in direct medical costs and $106.3 billion in indirect costs (ADA).

Those figures say nothing about your own denial rate. What it does mean is that a small coding habit, such as defaulting to E11.9, repeats on every diabetes claim it touches. Our guide to diabetic HCC coding covers how complication codes connect to risk adjustment.

Claim checks that catch diabetes coding errors

Most diabetes errors can be caught before submission by checking four things. Each one maps to a rule above, and each fits a standard clean claims review.

1. Type matches the note. E10 or E11 follows the provider’s wording, and the default to E11 applies only when no type is documented.
2. Every documented complication has its code. If the note mentions neuropathy, retinopathy, kidney disease or an ulcer, E11.9 or E10.9 should not be on the claim.
3. Z79 codes match the medication list. One per drug class, and none for insulin given only during the encounter.
4. No Excludes1 conflicts. E10 with E11, or either with an O24.4- gestational code, needs a reason or a query.

A coding audit is a structured way to run these checks on a sample of past claims. We explain the options in types of medical coding audits. Practices that bill for endocrinology services can see how these steps fit into a specialty workflow on the endocrinology billing and RCM page.

If diagnosis coding is slowing your billing team down, a medical billing service can take over coding support and claim review while your providers stay on documentation. Use the revenue calculator to estimate how much unpaid revenue a lower denial rate would recover.

Keeping up with yearly code changes

ICD-10-CM is updated every fiscal year, and diabetes codes can be affected. The E11.A remission code and the E10.A- presymptomatic type 1 codes covered above are examples of the category’s detail. The CDC publishes the FY2027 Tabular List and Index, addenda, code descriptions and the guidelines PDF each year in its ICD-10-CM files (CDC FY2027 file directory), and CMS links the same files on its ICD-10 page.

A short annual routine works for most practices: read the addenda for the E08 to E13 and O24 ranges, update the superbill and charge-capture picklists, and brief the coders and providers on any new options. Related endocrine and metabolic codes follow the same yearly cycle; see our guides to hypothyroidism ICD-10 coding and hyperlipidemia ICD-10 codes.

Our recommendations

1. Put the type and every complication in the assessment. Ask providers to write the diabetes type and each complication by name in the assessment, not only in the history. The code can only be as specific as the words.
2. Retire E11.9 as a picklist default. Keep E11.9 available, but do not let it sit at the top of the diabetes picklist. A default code invites claims that conflict with the rest of the chart.
3. Add Z79 prompts to the encounter template. A prompt that asks about insulin, oral and injectable drugs reduces missed Z79 codes. Add a note that temporary in-visit insulin is not long-term use.
4. Query, do not infer, for unclear wording. Terms like “uncontrolled,” “resolved” and “borderline” do not map cleanly to a code. A short provider query is cheaper than a denial or a record-review request.
5. Run a yearly diabetes claim sample. Pull a small sample of diabetes claims each fiscal year, compare codes to notes, and share the findings with providers and coders.

Bottom line

Diabetes coding comes down to the provider’s documented type, every documented complication, and the right Z79 codes. When your team wants help with coding support, claim review or denial management services, or just a second look at a sample of claims, you can talk to our team or request the free practice audit.

Frequently asked questions

What is the difference between E10 and E11 codes?

E10 is type 1 diabetes and E11 is type 2. Both use similar complication codes, such as E10.22 and E11.22 for diabetic chronic kidney disease. The provider’s documented type decides the category. If no type is documented, the guidelines say to default to E11. E10 and E11 are listed as Excludes1 for each other, so they are not normally reported together.

What ICD-10 code should I use if the provider only writes "diabetes"?

The FY2027 guidelines say to assign a code from E11 when the type of diabetes is not documented. Add Z79.4, Z79.84 or Z79.85 if the patient uses insulin, oral drugs or injectable non-insulin drugs. If the chart is unclear, a short query to the provider is better than an assumption.

Is E11.9 ever the wrong code?

Yes. E11.9 means type 2 diabetes without complications. If the note documents neuropathy, retinopathy, kidney disease, an ulcer or hyperglycemia, a more specific E11 code is needed instead, and E11.9 should not be reported alongside it. Check the full chart, not only the assessment line.

How do I code type 2 diabetes in remission?

Use E11.A when the provider documents type 2 diabetes in remission. The guidelines say to query the provider if remission is unclear, and they state that “resolved” is not the same as remission. Do not infer remission from a normal lab result alone.

Which code is used for gestational diabetes?

Gestational diabetes is reported with O24.4- codes. For example, O24.410 is diet controlled, O24.414 is insulin controlled, and O24.419 is unspecified control. It is not coded in E10 or E11, which list it under Excludes1. Use guideline section I.C.15 and the Tabular List for the full pregnancy rules.

How often do diabetes ICD-10 codes change?

ICD-10-CM updates each fiscal year, which for FY2027 runs from October 1, 2026 through September 30, 2027. Diabetes codes can change in any update, so review the addenda and guidelines each October. Match each claim to the code set in effect on the date of service.

Sources

1. ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027 — CDC / NCHS (2026)
2. ICD-10 codes (FY 2027 ICD-10-CM files) — CMS (2026)
3. ICD-10-CM FY2027 file directory — CDC / NCHS (2026)
4. E11 Type 2 diabetes mellitus (FY2027 listing) — icdlist.com (secondary mirror of CMS FY2027 data) (2026)
5. E10 Type 1 diabetes mellitus (FY2027 listing) — icdlist.com (secondary mirror of CMS FY2027 data) (2026)
6. O24.410 gestational diabetes (FY2027 listing) — veroscribe.com (secondary) (2026)
7. ICD-10 Diabetes Mellitus coding sheet — Qwick Coder / CWC Diabetes (via fhcp.com) (2017)
8. E11 child codes and notes (FY2027) — icd-10codes.com (secondary) (2026)
9. National Diabetes Statistics Report — CDC (2026)
10. The Cost of Diabetes — American Diabetes Association (2023)