ICD-10 Code E73.1 – Secondary lactase deficiency (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code E73.1 – Secondary lactase deficiency
What it is
Secondary lactase deficiency means reduced lactase activity caused by another intestinal condition or injury, not a primary inherited enzyme problem. It leads to temporary or persistent difficulty digesting lactose.
Clinical signs
Clinical features vary; refer to documentation. Commonly, patients report bloating, abdominal pain, gas, and diarrhea after lactose intake, especially when an underlying gastrointestinal disorder is present.
When to use this code
Use this code when the record states lactase deficiency is secondary to another condition, such as intestinal inflammation, infection, or mucosal injury. You may also use it when the clinician documents lactose intolerance due to a known acquired cause. Check documentation for the underlying disorder, because it should be coded separately when documented.
Do not use for
Do not use this code for primary lactase deficiency or nonspecific lactose intolerance without evidence of an acquired cause. If the chart does not link the deficiency to another condition, check documentation.
Coding tip
Code the underlying intestinal condition first when it is documented, and use E73.1 only when secondary lactase deficiency is clearly stated.