What is the ICD-10 (International Classification of Diseases, 10th Revision) code for Hemoglobin A1c (HbA1c) in a patient with Type 2 diabetes mellitus?

ICD-10 Codes for Hemoglobin A1c Testing

The ICD-10 code for ordering or documenting a Hemoglobin A1c test depends on the clinical context, but for a patient with Type 2 diabetes mellitus, use Z13.1 (encounter for screening for diabetes mellitus) for screening purposes, or the specific diabetes code (E11.65 for Type 2 diabetes with hyperglycemia, E11.9 for Type 2 diabetes without complications) when monitoring established disease.

Primary ICD-10 Codes for A1c Testing Context

For Established Type 2 Diabetes

• E11.9 - Type 2 diabetes mellitus without complications (most common code when A1c is used for routine monitoring) 1
• E11.65 - Type 2 diabetes mellitus with hyperglycemia (when A1c is elevated and hyperglycemia is documented) 1
• E11.8 - Type 2 diabetes mellitus with unspecified complications (when complications exist but are not specified) 1

For Screening Purposes

• Z13.1 - Encounter for screening for diabetes mellitus (when ordering A1c as a screening test in at-risk patients without established diabetes) 1
• R73.03 - Prediabetes (when A1c is 5.7-6.4% and used to document prediabetic state) 1

Clinical Context for Code Selection

When Monitoring Established Diabetes

• Use the appropriate E11.x code based on the patient's diabetes status and complications 1
• A1c should be performed at least twice yearly in patients meeting treatment goals, or quarterly when therapy has changed or goals are not met 1
• The A1c target for most nonpregnant adults is <7% (53 mmol/mol), which corresponds to this monitoring indication 1

When Diagnosing New Diabetes

• E11.9 is appropriate when A1c ≥6.5% confirms new diagnosis of Type 2 diabetes 1
• The diagnosis should be confirmed with repeat testing unless clinical hyperglycemia is unequivocal 1
• A1c ≥6.5% is one of four acceptable diagnostic criteria for diabetes mellitus 1

Important Coding Considerations

Documentation Requirements

• The medical record should specify whether A1c is being used for screening, diagnosis, or monitoring of established disease 1
• Document the actual A1c value and its relationship to treatment goals (e.g., "A1c 7.8%, above target of <7%") 1
• For insurance purposes, the diagnosis code must match the clinical indication for the test 1

Common Pitfalls to Avoid

• Do not use Z13.1 for patients with established diabetes—this is only for screening in at-risk individuals without known disease 1
• Do not use R73.09 (other abnormal glucose) when a specific diabetes diagnosis exists 1
• Ensure the code reflects current clinical status; if A1c confirms diabetes, use E11.x codes, not screening codes 1

Special Populations

• For Type 1 diabetes, use E10.x codes instead of E11.x 1
• For gestational diabetes or diabetes in pregnancy, use O24.x codes 1
• For patients with chronic kidney disease and diabetes, use E11.22 (Type 2 diabetes with diabetic chronic kidney disease) when monitoring A1c in this context 1