ICD-10 code for type 2 diabetes (E11)

Type 2 diabetes mellitus is coded under category E11 in ICD-10-CM. E11 itself is a category header, not a code you can submit on a claim — you always have to go one level more specific, to a code that says whether the diabetes is uncomplicated or names the complication it's causing.

The default: E11.9

E11.9 — "Type 2 diabetes mellitus without complications" — is the billable code for a straightforward diagnosis with no documented complication. It's the most commonly used code in the E11 family and the right default when the chart doesn't support anything more specific.

Coding a documented complication

ICD-10-CM wants you to capture the complication, not just "diabetes," whenever the record supports it. The E11 category branches by complication type:

• E11.21 — with diabetic nephropathy; E11.22 — with diabetic chronic kidney disease (kidney complications).
• E11.311 — with unspecified diabetic retinopathy with macular edema, and related E11.3- codes (eye complications).
• E11.40 — with diabetic neuropathy, unspecified; E11.42 — with diabetic polyneuropathy (neurological complications).
• E11.51 — with diabetic peripheral angiopathy without gangrene (circulatory complications).
• E11.65 — with hyperglycemia (a very frequently used code when blood glucose control is the documented issue).

Each of those is a specific, billable leaf code — not a header — because it names the complication rather than leaving it generic. If a patient has more than one documented complication, ICD-10-CM guidelines call for coding each one, not just the most severe.

Why E11 alone gets rejected

Payers validate that a submitted diagnosis code is a billable (leaf) code, not a category header. E11 is a header — it exists to organize the family, not to be billed — so a claim submitted with bare "E11" instead of "E11.9" or a complication code will typically be rejected or returned for correction. This is one of the most common denial reasons in diabetes coding, and it's avoidable by always coding to the fourth character or beyond.

Type 1 vs type 2 — don't mix up the category

Type 1 diabetes lives under a different category, E10, with a parallel structure of complication codes (E10.9, E10.21, E10.65, and so on). Type 2 is E11; there's also E08 (diabetes due to an underlying condition), E09 (drug- or chemical-induced diabetes), and E13 (other specified diabetes) — all mirroring the same complication-code pattern, so the family you learn under E11 largely carries over.

For developers and agents

If you're generating or validating diagnosis codes programmatically, don't let a model guess a subcode from memory — hallucinated ICD-10 codes look plausible and fail silently until a claim bounces. `GET /api/v1/icd10/E11.9` returns the official description, billable flag, chapter and parent for any code in the family, and `GET /api/v1/icd10?q=type%202%20diabetes&billable=1` returns only the leaf codes that are actually valid to submit.