ICD-10 Code E73.0 – Congenital lactase deficiency (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code E73.0 – Congenital lactase deficiency
What it is
E73.0 identifies congenital lactase deficiency, a rare inherited disorder in which the intestine cannot make enough lactase to digest lactose. It is present from birth and causes intolerance to breast milk or standard formula.
Clinical signs
Clinical features vary; refer to documentation. Typical findings include watery diarrhea, abdominal distension, and feeding intolerance soon after lactose exposure in an infant. Diagnosis is usually based on the clinical picture and exclusion of other causes.
When to use this code
Use this code when the provider documents congenital lactase deficiency or congenital alactasia. You may also use it when the chart clearly describes a lifelong inability to digest lactose beginning in the newborn period. Code only when the condition is specifically identified.
Do not use for
Do not use this code for acquired lactose intolerance, secondary lactase deficiency, or nonspecific infant diarrhea. Check documentation if the record only mentions milk intolerance without confirming the congenital disorder.
Coding tip
Confirm that the diagnosis is congenital and not secondary before assigning E73.0.