2026 ICD-10-CM Diagnosis Code E73.1Secondary lactase deficiency

ICD-10-CM Codes›E00–E89›E70-E88›E73

ICD-10-CM E73.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

E73.1 is a billable ICD-10-CM diagnosis code for secondary lactase deficiency. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 391 through 392. Coders also document this condition as acquired lactase deficiency. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified nutritional and metabolic disorders.

Code Identity

ICD-10-CM Code
E73.1
Billable Status
Yes — Valid for Submission
Code Describes
Secondary lactase deficiency
Short Description
Secondary lactase deficiency
Same as the full description in the CMS dataset.
Parent Code
E73
Lactose intolerance

Code Classification

ChapterE00–E89Endocrine, nutritional and metabolic diseases
SectionE70-E88Metabolic disorders
CategoryE73Lactose intolerance
This CodeE73.1Secondary lactase deficiency

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acquired lactase deficiency
  • Intolerance to lactose
  • Intolerance to lactose due to lactase deficiency in diseases other than of the small intestine
  • Lactase deficiency

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Deficiency, deficient
      • lactase
        • secondary

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR END016
Other specified and unspecified nutritional and metabolic disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Lactose Intolerance

    the condition resulting from the absence or deficiency of lactase in the mucosa cells of the gastrointestinal tract, and the inability to break down lactose in milk for absorption. bacterial fermentation of the unabsorbed lactose leads to symptoms that range from a mild indigestion (dyspepsia) to severe diarrhea. lactose intolerance may be an inborn error or acquired.

Patient EducationClinical

Lactose Intolerance

Lactose intolerance means that you cannot digest foods with lactose in them. Lactose is the sugar found in milk and foods made with milk. After eating foods with lactose in them, you may feel sick to your stomach. You may also have:

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert E73.1 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
271.3 Disaccharidase def/malab
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About E73.1Overview

Is E73.1 (Lactose intolerance) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report secondary lactase deficiency on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does E73.1 group to?

When secondary lactase deficiency is the principal diagnosis on an inpatient stay, it groups to MS-DRG 391, 392, with relative weights from 0.7796 to 1.2683 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of E73.1?

Under the General Equivalence Mappings, secondary lactase deficiency converts to ICD-9-CM 271.3 (disaccharidase def/malab). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.