ICD-10 Code K63.821 – Small intestinal bacterial overgrowth (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code K63.821 – Small intestinal bacterial overgrowth
What it is
K63.821 identifies small intestinal bacterial overgrowth, a condition where excess bacteria are present in the small intestine. Use it when the diagnosis is documented and the record supports SIBO specifically.
Clinical signs
Clinical features vary; refer to documentation. Commonly noted findings include bloating, abdominal discomfort, diarrhea, and malabsorption-related complaints, but you should code only when the provider documents SIBO.
When to use this code
Use K63.821 when the clinician diagnoses small intestinal bacterial overgrowth, including confirmed or suspected SIBO documented in the assessment. It may also fit follow-up visits for ongoing management of the condition. If the note describes nonspecific gastrointestinal symptoms without a stated diagnosis, check documentation.
Do not use for
Do not use this code for general abdominal bloating, diarrhea, or other symptoms without a documented SIBO diagnosis. Do not assign it when another cause of malabsorption or intestinal symptoms is specifically identified.
Coding tip
Code K63.821 only when the provider names small intestinal bacterial overgrowth in the chart; otherwise, query or code the documented symptom.