E51.2 ICD-10-CM Code: Wernicke's encephalopathy

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for E51.2 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 E51.2 itself; “inherited from” names the category or block whose note applies here.

Coder workflow for E51.2

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

Before you code E51.2

1. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with E51.2. 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 documentation support a condition named in E51.2’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.

   ReviewE64.8

Consider E51.2. 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).

Official instructions as workflow

• Excludes1 — check before selecting E51.2(1 note)

  Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with E51.2: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

  CompareE64.8

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

• Excludes2 — not part of E51.2(1 note)

  Coding workflow: The conditions named in this note are not included in E51.2. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

  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

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.

Indexed Clinical Terms (11)

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.

• Degeneration, degenerative, brain (cortical) (progressive), in, beriberi
• Encephalopathy (acute), vitamin B deficiency NEC, vitamin B1
• Encephalopathy (acute), Wernicke's
• Hemorrhage, hemorrhagic (concealed), polioencephalitis, superior
• Polioencephalitis (acute) (bulbar), superior hemorrhagic (acute) (Wernicke's)
• Polioencephalitis (acute) (bulbar), Wernicke's
• Polioencephalomyelitis (acute) (anterior), with beriberi
• Polioencephalopathy, superior hemorrhagic
• Wernicke's, disease or syndrome
• Wernicke's, encephalopathy
• Wernicke's, polioencephalitis, superior

Don’t confuse E51.2 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of E51.2 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

• E64.8— Excludes1 conflict (Excludes1 — generally not reported together)

  Not coded here — the tabular list excludes this pair for the same encounter.

  Not reported together with this code, except where the two conditions are documented as unrelated.

  What moves you there: Documentation of sequelae of thiamine deficiency moves the case to E64.8; the two are not reported together unless documented as unrelated.

  Full comparison: E51.2 vs E64.8 →

• E51.9— Specificity relationship (Review)

  Overlapping diagnoses in the same category.

  Overlapping codes in the same category — the documentation decides which is the more specific fit.

  What moves you there: A record that documents no more than “Thiamine deficiency, unspecified” takes E51.9; specificity in the record moves it back here.

  Full comparison: E51.2 vs E51.9 →

• D50— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of nutritional anemias adds D50; it is not part of this code and both may be reported when both are documented.

  Full comparison: E51.2 vs D50 →

• D53— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of nutritional anemias adds D53; it is not part of this code and both may be reported when both are documented.

  Full comparison: E51.2 vs D53 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Verify Before Coding

• CC as a secondary diagnosis (FY2026). Can raise the stay's MS-DRG severity tier.

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 E51.2 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 3 Excludes1 notes across 3 chapters: G32.8 — Other specified degenerative disorders of nervous system in diseases classified elsewhere, T45.2X6 — Underdosing of vitamins (via E51.-), Z72.4 — Inappropriate diet and eating habits (via E51.-).

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

Referenced by 1 Code First instruction: G63 — Polyneuropathy in diseases classified elsewhere (via E51.-).

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: CC — Complication or Comorbidity. Reported as a secondary diagnosis, this code raises the stay's MS-DRG severity tier — except when the principal diagnosis is one of 34 clinically related codes on its CMS exclusion list.

Named in the grouper logic of 2 MS-DRGs: DRG 640 (MDC 10), DRG 641 (MDC 10).

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

Clinical classification (AHRQ CCSR):END007 — Nutritional deficiencies (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 process (MS-DRG)

Acts as CC — raises the severity of other admissions. CMS groups these diagnoses into one MS-DRG principal-diagnosis exclusion process — a CC/MCC on this list never raises severity when the principal diagnosis is also on it.

D81.818 — Other biotin-dependent carboxylase deficiency, D81.819 — Biotin-dependent carboxylase deficiency, unspecified, E51.11 — Dry beriberi, E51.12 — Wet beriberi, E51.8 — Other manifestations of thiamine deficiency, E51.9 — Thiamine deficiency, unspecified, E52 — Niacin deficiency [pellagra], E53.0 — Riboflavin deficiency, E53.1 — Pyridoxine deficiency, E53.8 — Deficiency of other specified B group vitamins, E53.9 — Vitamin B deficiency, unspecified, E56.0 — Deficiency of vitamin E, E56.8 — Deficiency of other vitamins, E56.9 — Vitamin deficiency, unspecified, E58 — Dietary calcium deficiency, E59 — Dietary selenium deficiency, E60 — Dietary zinc deficiency, E61.0 — Copper deficiency, E61.1 — Iron deficiency, E61.2 — Magnesium deficiency, +13 more

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Nutritional deficiencies).

E50.2 — Vitamin A deficiency with corneal xerosis, E50.3 — Vitamin A deficiency with corneal ulceration and xerosis, E50.4 — Vitamin A deficiency with keratomalacia, E50.5 — Vitamin A deficiency with night blindness, E50.6 — Vitamin A deficiency with xerophthalmic scars of cornea, E50.7 — Other ocular manifestations of vitamin A deficiency, E50.8 — Other manifestations of vitamin A deficiency, E50.9 — Vitamin A deficiency, unspecified, E51.11 — Dry beriberi, E51.12 — Wet beriberi, E51.8 — Other manifestations of thiamine deficiency, E51.9 — Thiamine deficiency, unspecified, E52 — Niacin deficiency [pellagra], E53.0 — Riboflavin deficiency, E53.1 — Pyridoxine deficiency, E53.8 — Deficiency of other specified B group vitamins, E53.9 — Vitamin B deficiency, unspecified, E54 — Ascorbic acid deficiency, E55.0 — Rickets, active, E55.9 — Vitamin D deficiency, unspecified, +23 more

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main terms “Encephalopathy”, “Degeneration, degenerative”, “Wernicke's”, …; these codes share that main term but sit in a different category of the Tabular List.

E03.9 — Hypothyroidism, unspecified (brain, in, myxedema), E07.89 — Other specified disorders of thyroid (thyroid), E16.1 — Other hypoglycemia (posthypoglycemic), E16.2 — Hypoglycemia, unspecified (hypoglycemic), E21.4 — Other specified disorders of parathyroid gland (parathyroid), E23.6 — Other disorders of pituitary gland (pituitary), E27.49 — Other adrenocortical insufficiency (adrenal), E27.8 — Other specified disorders of adrenal gland (adrenal), E32.8 — Other diseases of thymus (thymus), E34.8 — Other specified endocrine disorders (pineal gland), E52 — Niacin deficiency [pellagra] (pellagrous), E53.8 — Deficiency of other specified B group vitamins (combined), E53.9 — Vitamin B deficiency, unspecified (vitamin B deficiency NEC), E56.9 — Vitamin deficiency, unspecified (in, lack of vitamin), E75.21 — Fabry (-Anderson) disease (brain, in, Fabry-Anderson disease), E75.22 — Gaucher disease (brain, in, Gaucher's disease), E75.249 — Niemann-Pick disease, unspecified (brain, in, Niemann-Pick disease), E75.3 — Sphingolipidosis, unspecified (brain, in, sphingolipidosis), E75.4 — Neuronal ceroid lipofuscinosis (brain, in, lipidosis, cerebral), E75.6 — Lipid storage disorder, unspecified (brain, in, lipidosis, generalized), +320 more

Contextual Map

Every relationship of E51.2 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 E51.2 with these 4 related codes in Claim Check

Hierarchy

• E00-E89 — Chapter 4: Endocrine, Nutritional and Metabolic Diseases (E00-E89) (E00-E89)[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• E50-E64 — Other nutritional deficiencies[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Referenced by Excludes1 notes

• G32.8 — Other specified degenerative disorders of nervous system in diseases classified elsewhere[Excludes1]: “superior hemorrhagic polioencephalitis [Wernicke's encephalopathy] (E51.2)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• T45.2X6 — Underdosing of vitamins[Excludes1](via E51.-): “vitamin deficiencies (E50-E56)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• Z72.4 — Inappropriate diet and eating habits[Excludes1](via E51.-): “malnutrition and other nutritional deficiencies (E40-E64)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Referenced by Code First instructions

• G63 — Polyneuropathy in diseases classified elsewhere[Code First](via E51.-): “nutritional deficiency (E40-E64)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Clinical classification (CCSR)

• END007 — Nutritional deficiencies[CCSR]— AHRQ CCSR for ICD-10-CM Diagnoses (HCUP)

MS-DRG Grouper

• CC — Complication or Comorbidity [MS-DRG severity]: “As a secondary diagnosis this code can raise the stay's MS-DRG severity tier (CC).”— CMS MS-DRG Definitions Manual (Appendix C) · FY2026
• DRG 640 — MISCELLANEOUS DISORDERS OF NUTRITION, METABOLISM, FLUIDS AND ELECTROLYTES WITH MCC[MS-DRG]: “MISCELLANEOUS DISORDERS OF NUTRITION, METABOLISM, FLUIDS AND ELECTROLYTES WITH MCC (MDC 10)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026
• DRG 641 — MISCELLANEOUS DISORDERS OF NUTRITION, METABOLISM, FLUIDS AND ELECTROLYTES WITHOUT MCC[MS-DRG]: “MISCELLANEOUS DISORDERS OF NUTRITION, METABOLISM, FLUIDS AND ELECTROLYTES WITHOUT MCC (MDC 10)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026

MDC crossing

• MDC 10 — Endocrine, Nutritional and Metabolic Diseases and Disorders[MDC crossing]: “Endocrine, Nutritional and Metabolic Diseases and Disorders — 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. 5,008 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026

Index entries (11)

• Degeneration, degenerative, brain (cortical) (progressive), in, beriberi[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Encephalopathy (acute), vitamin B deficiency NEC, vitamin B1[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Encephalopathy (acute), Wernicke's[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Hemorrhage, hemorrhagic (concealed), polioencephalitis, superior[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Polioencephalitis (acute) (bulbar), superior hemorrhagic (acute) (Wernicke's)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Polioencephalitis (acute) (bulbar), Wernicke's[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Polioencephalomyelitis (acute) (anterior), with beriberi[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Polioencephalopathy, superior hemorrhagic[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• and 3 more

Nearest codes

• E51 — Thiamine deficiency[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• E51.1 — Beriberi[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• E51.11 — Dry beriberi[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• E51.12 — Wet beriberi[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• E51.8 — Other manifestations of thiamine deficiency[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• E51.9 — Thiamine deficiency, unspecified[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

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

Nearest Codes in This Family

Official ICD-10-CM classifications closest to E51.2 in its code family, with their registry titles.

• E51 — Thiamine deficiency
• E51.1 — Beriberi
• E51.11 — Dry beriberi
• E51.12 — Wet beriberi
• E51.8 — Other manifestations of thiamine deficiency
• E51.9 — Thiamine deficiency, unspecified

View all codes in the E51 family