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E73.9 ICD-10-CM Code: Lactose intolerance, unspecified

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Coding at a Glance

Tabular directives
5 Excludes1 · 1 Excludes2

Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v43, Appendix B.

  • MS-DRG 391 — ESOPHAGITIS, GASTROENTERITIS AND MISCELLANEOUS DIGESTIVE DISORDERS WITH MCC (MDC 06)
  • MS-DRG 392 — ESOPHAGITIS, GASTROENTERITIS AND MISCELLANEOUS DIGESTIVE DISORDERS WITHOUT MCC (MDC 06)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for E73.9 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Notes without a marker are published on E73.9 itself; “inherited from” names the category or block whose note applies here.

Excludes1 — Not Coded Here

Conditions generally not reported together with this code (Excludes1) -- an error unless the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Source: inherited from E70-E88

Excludes2 — Not Included Here

Conditions not covered by this code, but which may be reported alongside it when both are present.

Source: inherited from E70-E88

Coder workflow for E73.9

MedCoder structured workflow — derived from this code’s own official record

Before you code E73.9

  1. Unspecified does not mean incorrect. When the record gives no greater specificity, E73.9 may be the appropriate code. Check the record for detail that supports a more specific sibling. An unspecified code is for records that do not provide the detail a more specific code needs; a query, not an assumption, is the route to specificity (Guidelines I.A.9.b, I.B.18).

    ReviewE73.0, E73.1, E73.8

    See the relationships section · Guide: Other vs unspecified (NEC vs NOS) →

  2. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with E73.9. Excludes1 conditions are not reported together with this code unless the record shows they are unrelated (Guidelines I.A.12.a).

    See the official tabular notes

Choose the right path

  1. Does the record document the detail a more specific sibling code needs?
    Yes → Review the specific siblings in this subcategory.
    No → Continue — E73.9 is appropriate when the documentation goes no further.

    ReviewE73.0, E73.1, E73.8

  2. Does the documentation support a condition named in E73.9’s Excludes1 note?
    Yes → Do not simply proceed: review the excluded code. Both are reported only when the record shows the two conditions are unrelated.
    No → Continue.

    ReviewE34.5, E25.0, D55, Q87.4, E29.1

Consider E73.9. Then confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement
Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).
Any detail beyond this code’s title
What the record states that a more specific sibling code would capture — or its absence, which itself supports the unspecified code.

Official instructions as workflow

  • Excludes1 — check before selecting E73.9(5 notes)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with E73.9: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareE34.5, E25.0, D55, Q87.4, E29.1

    See the official tabular notes · Guidelines I.A.12.a

  • Excludes2 — not part of E73.9(1 note)

    Coding workflow: The conditions named in this note are not included in E73.9. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

    CompareQ79.6

    See the official tabular notes · Guidelines I.A.12.b

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Documentation: The provider documents the condition in the terms of this code’s title and records no further detail.

Coding question: Is a more specific sibling code supportable?

Path: Review the specific siblings in this subcategory and what each requires the record to state.

Reason: A more specific code needs documentation of the distinguishing element; without it the unspecified code is appropriate, and a provider query is the route to specificity (Guidelines I.A.9.b, I.B.18).

ReviewE73.0, E73.1, E73.8

Documentation: Both the condition E73.9 describes and a condition named in its Excludes1 note are documented for the same encounter.

Coding question: Can both codes be reported?

Path: Review the Excludes1 note and the excluded code, and look for a provider statement on whether the two conditions are related.

Reason: Excludes1 means the two are not coded together; the exception is when the record shows the conditions are unrelated to each other (Guidelines I.A.12.a).

ReviewE34.5, E25.0, D55, Q87.4, E29.1

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Code Overview

Lactose intolerance, unspecified is a billable ICD-10-CM diagnosis code (E73.9).

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Indexed Clinical Terms (5)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

Verify Before Coding

  • No Medicare Code Editor or MS-DRG Definitions Manual restrictions apply to this code.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name E73.9 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 7 Excludes1 notes across 3 chapters: P59 — Neonatal jaundice from other and unspecified causes (via E73.-), R79 — Other abnormal findings of blood chemistry (via E73.-), R80 — Proteinuria (via E73.-), R80-R82 — Abnormal findings on examination of urine, without diagnosis (R80-R82) (via E73.-), R81 — Glycosuria (via E73.-), R82 — Other and unspecified abnormal findings in urine (via E73.-), Z91.011 — Allergy to milk products (via E73.-).

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Referenced by 6 Excludes2 notes across 4 chapters: E74.3 — Other disorders of intestinal carbohydrate absorption (via E73.-), G11 — Hereditary ataxia (via E73.-), G71 — Primary disorders of muscles (via E73.-), K90.4 — Other malabsorption due to intolerance (via E73.-), N25.0 — Renal osteodystrophy (via E73.-), N25.81 — Secondary hyperparathyroidism of renal origin (via E73.-).

These codes’ tabular lists name this diagnosis as distinct — both may be reported when both are documented.

Referenced by 2 Code First instructions across 2 chapters: G63 — Polyneuropathy in diseases classified elsewhere (via E73.-), H42 — Glaucoma in diseases classified elsewhere (via E73.-).

Each of these codes carries a Code First note naming this condition — when that code is reported, THIS code is sequenced first, ahead of it.

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity for that release.

Named in the grouper logic of 2 MS-DRGs: DRG 391 (MDC 06), DRG 392 (MDC 06).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):END016 — Other specified and unspecified nutritional and metabolic disorders (default).

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Other specified and unspecified nutritional and metabolic disorders).

E72.548 — Other secondary hyperoxaluria, E72.549 — Secondary hyperoxaluria, unspecified, E72.59 — Other disorders of glycine metabolism, E72.8 — Other specified disorders of amino-acid metabolism, E72.81 — Disorders of gamma aminobutyric acid metabolism, E72.89 — Other specified disorders of amino-acid metabolism, E72.9 — Disorder of amino-acid metabolism, unspecified, E73.0 — Congenital lactase deficiency, E73.1 — Secondary lactase deficiency, E73.8 — Other lactose intolerance, E74.00 — Glycogen storage disease, unspecified, E74.01 — von Gierke disease, E74.02 — Pompe disease, E74.03 — Cori disease, E74.04 — McArdle disease, E74.05 — Lysosome-associated membrane protein 2 [LAMP2] deficiency, E74.09 — Other glycogen storage disease, E74.10 — Disorder of fructose metabolism, unspecified, E74.11 — Essential fructosuria, E74.12 — Hereditary fructose intolerance, +258 more

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main terms “Deficiency, deficient”, “Intolerance”, “Malabsorption”; these codes share that main term but sit in a different category of the Tabular List.

E71.41 — Primary carnitine deficiency (carnitine, primary), E71.42 — Carnitine deficiency due to inborn errors of metabolism (carnitine, due to, inborn errors of metabolism), E71.43 — Iatrogenic carnitine deficiency (carnitine, iatrogenic), E71.448 — Other secondary carnitine deficiency (carnitine, secondary), E72.12 — Methylenetetrahydrofolate reductase deficiency (methylenetetrahydrofolate reductase), E72.19 — Other disorders of sulfur-bearing amino-acid metabolism (methionine), E72.3 — Disorders of lysine and hydroxylysine metabolism (lysine), E72.4 — Disorders of ornithine metabolism (ornithine transcarbamylase), E72.81 — Disorders of gamma aminobutyric acid metabolism (GABA-T), E72.9 — Disorder of amino-acid metabolism, unspecified (amino-acids), E74.01 — von Gierke disease (glucose-6-phosphatase), E74.02 — Pompe disease (lysosomal alpha-1, 4 glucosidase), E74.03 — Cori disease (brancher enzyme), E74.04 — McArdle disease (myophosphorylase), E74.05 — Lysosome-associated membrane protein 2 [LAMP2] deficiency (lysosome-associated membrane protein 2 [LAMP2]), E74.09 — Other glycogen storage disease (hepatophosphorylase), E74.10 — Disorder of fructose metabolism, unspecified (fructose), E74.11 — Essential fructosuria (fructokinase), E74.12 — Hereditary fructose intolerance (fructose, hereditary), E74.19 — Other disorders of fructose metabolism (aldolase), +185 more

Lab tests where this diagnosis supports Medicare coverage (NCD)

Medicare's National Coverage Determination (NCD) program lists this diagnosis as medical justification for these lab tests.

Blood Glucose Test

Contextual Map

Every relationship of E73.9 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run E73.9 with these 15 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes

Referenced by Excludes2 notes

Referenced by Code First instructions

Clinical classification (CCSR)

MS-DRG Grouper

MDC crossing

  • MDC 06 — Diseases and Disorders of the Digestive System[MDC crossing]: “Diseases and Disorders of the Digestive System — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 5,744 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026

Index entries

  • Deficiency, deficient, disaccharidase[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Intolerance, lactose[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Intolerance, milk NEC, lactose[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Malabsorption, disaccharide[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Malabsorption, lactose[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes

Change history

  • FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page
Inpatient payment groups Official source data
CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v43 Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder structured relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "E73.9 — Lactose intolerance, unspecified." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/e73.9-lactose-intolerance-unspecified

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Lactose intolerance, unspecified

No changes since FY2016 — additions, deletions, description changes and billable-status changes are tracked through FY2027 (effective October 1, 2026), and none are recorded for this code. Note changes are tracked from FY2027 only.

Nearest Codes in This Family

Official ICD-10-CM classifications closest to E73.9 in its code family, with their registry titles.

View all codes in the E73 family