E11.9 — Type 2 diabetes mellitus without complications

Clinical Definition

Type 2 diabetes mellitus is a chronic metabolic disorder characterized by peripheral insulin resistance, relative insulin deficiency, and resultant hyperglycemia. It accounts for approximately 90-95% of all diabetes cases and is strongly associated with obesity, physical inactivity, advancing age, and genetic predisposition. The pathophysiology involves progressive decline in pancreatic beta-cell function combined with impaired insulin signaling in skeletal muscle, liver, and adipose tissue. Patients may be asymptomatic for years, with the condition frequently detected through routine screening or incidental findings of elevated fasting glucose or hemoglobin A1c.

ICD-10-CM code E11.9 is assigned when the provider documents type 2 diabetes mellitus without associated complications — meaning the patient does not have documented diabetic nephropathy, retinopathy, neuropathy, peripheral vascular disease, or other end-organ manifestations attributable to diabetes. This code is also the default when documentation states 'diabetes mellitus' or 'diabetes' without specifying type, per ICD-10-CM Official Guidelines Section I.A.15. It should not be used when the provider has documented any diabetic complication; the appropriate combination code from E11.0-E11.8 must be assigned instead.

Diagnosis follows American Diabetes Association criteria: fasting glucose >= 126 mg/dL, 2-hour OGTT glucose >= 200 mg/dL, HbA1c >= 6.5%, or random glucose >= 200 mg/dL with classic hyperglycemic symptoms. Management includes lifestyle modification, oral hypoglycemics (metformin first-line), injectable therapies (GLP-1 agonists, insulin), and ongoing complication surveillance.

When to Use E11.9

• ✓The provider documents 'type 2 diabetes mellitus' without any documented end-organ complications such as nephropathy, retinopathy, neuropathy, or peripheral vascular disease.
• ✓The documentation states 'diabetes mellitus' or 'diabetes' without specifying type — per ICD-10-CM guidelines, the default assignment is E11.9 (type 2 diabetes without complications).
• ✓The patient is on oral hypoglycemic agents or lifestyle management for type 2 diabetes, and the encounter documentation confirms no active diabetic complications.
• ✓The patient has type 2 diabetes that is documented as 'well-controlled,' 'stable,' or 'uncomplicated,' with no concurrent diabetic complication codes supported by the clinical record.
• ✓The provider documents 'uncontrolled type 2 diabetes' or 'inadequately controlled type 2 diabetes' without specifying hyperglycemia or hypoglycemia — E11.9 may be assigned, though E11.65 (with hyperglycemia) should be queried if clinically appropriate.
• ✓A pre-operative or pre-procedural evaluation documents type 2 diabetes as a comorbidity without associated complications — E11.9 is assigned as a secondary diagnosis.

Common Coding Mistakes

Related & Differential Codes

Documentation Requirements

• 1Diabetes type: explicitly document 'type 2 diabetes mellitus' — if the type is not specified, ICD-10-CM guidelines default to type 2 (E11), but explicit documentation prevents coding ambiguity and audit risk.
• 2Complication status: clearly state whether the diabetes is with or without complications. If no complications are present, document 'without complications' or 'uncomplicated.' If complications exist, document each specific complication (nephropathy, retinopathy, neuropathy, etc.) and its causal relationship to diabetes.
• 3Glycemic control: document the current level of control — 'well-controlled,' 'inadequately controlled,' or 'uncontrolled' — along with the most recent HbA1c value and date. If hyperglycemia or hypoglycemia is present, document it explicitly to support E11.65 or E11.649 rather than E11.9.
• 4Current medications: document all diabetes-related medications including oral hypoglycemics, GLP-1 receptor agonists, and insulin. If the patient uses insulin for type 2 diabetes, this supports the addition of Z79.4 (long-term current use of insulin).
• 5Comorbid conditions: document associated conditions such as hypertension (I10), obesity (E66.xx), dyslipidemia (E78.5), and metabolic syndrome, as these are frequently coded alongside E11.9 and affect risk adjustment.
• 6Screening and monitoring results: include most recent HbA1c, fasting glucose, lipid panel, urine albumin-to-creatinine ratio, and annual diabetic eye exam and foot exam findings to demonstrate ongoing complication surveillance.
• 7Body mass index: document the patient's BMI and corresponding ICD-10 code (Z68.xx) at each encounter, as obesity is a significant comorbidity affecting treatment decisions and risk stratification.
• 8Treatment plan and goals: document the individualized treatment plan including glycemic targets, lifestyle modifications, medication adjustments, and referrals to diabetes education, nutrition counseling, ophthalmology, or podiatry.

Reimbursement & Billing Notes

ICD-10-CM code E11.9 is a valid, billable code accepted by Medicare, Medicaid, and all commercial payers for encounters involving type 2 diabetes mellitus without complications. It is one of the most frequently reported diagnosis codes in the United States. E11.9 maps to CMS-HCC category 37 (Diabetes without Complication) in the V28 risk adjustment model, carrying an HCC risk coefficient that affects Medicare Advantage capitation payments. This makes accurate reporting of E11.9 essential for risk adjustment — the code must be supported by face-to-face encounter documentation and reported at least annually for each patient to maintain HCC capture.

Because E11.9 represents the lowest-severity diabetes HCC, auditors and payers will scrutinize claims where the patient's medical record suggests unaddressed complications. If the patient has documented CKD, retinopathy, neuropathy, or peripheral vascular disease, failing to link these to diabetes (when clinically appropriate) both understates risk and invites audit inquiries. Conversely, upcoding from E11.9 to a complication code without supporting documentation is a significant compliance risk under the False Claims Act. Providers should ensure that each encounter note clearly documents the presence or absence of diabetic complications and that the HbA1c and complication screening results are current. For value-based care and quality reporting programs (HEDIS, MIPS), E11.9 triggers diabetes-specific quality measures including HbA1c control, eye exam completion, and nephropathy screening rates.

Frequently Asked Questions