R40.20 ICD-10-CM Code: Unspecified coma

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for R40.20 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 R40.20 itself; “inherited from” names the category or block whose note applies here.

Coder workflow for R40.20

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

Before you code R40.20

1. Check whether an established diagnosis that explains this sign or symptom is documented. If one is, review whether the documented diagnosis changes the coding pathway: a symptom that is integral to a confirmed diagnosis is not reported separately, while one not routinely associated with it may be. Signs and symptoms are reported when no definitive diagnosis is established (Guidelines I.B.4, I.B.5, I.B.6, I.C.18.b).

   Guide: Symptom code vs confirmed diagnosis →

2. Unspecified does not mean incorrect. When the record gives no greater specificity, R40.20 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).

   ReviewR40.21, R40.22

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

3. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with R40.20. 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. Is an established diagnosis that explains this sign or symptom documented?
   Yes → Review whether the documented diagnosis changes the coding pathway: a symptom integral to it is not reported separately.
   No → Continue — the sign or symptom code stands when no definitive diagnosis is established.
2. Does the record document the detail a more specific sibling code needs?
   Yes → Review the specific siblings in this subcategory.
   No → Continue — R40.20 is appropriate when the documentation goes no further.

   ReviewR40.21, R40.22

3. Does the documentation support a condition named in R40.20’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.

   ReviewP91.5, K72, E15

4. Is the underlying (etiologic) condition the Code First note names documented?
   Yes → Sequence the underlying condition first, then R40.20.
   No → Continue; do not add an underlying condition the record does not document.

   ReviewS02, S06

Consider R40.20. 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).

The underlying (etiologic) condition

Named in the Code First note; sequenced before this code when documented (Guidelines I.A.13).

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 R40.20(4 notes)

  Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with R40.20: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

  CompareP91.5, K72, E15

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

• Excludes2 — not part of R40.20(1 note)

  Coding workflow: The conditions named in this note are not included in R40.20. 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

• Code First — sequencing check(3 notes)

  Coding workflow: Check whether the underlying or etiologic condition the note names is documented. When it is, sequence it before R40.20. Do not add an underlying condition the record does not document.

  ReviewS02, S06

  See the official tabular notes · Guidelines I.A.13

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 (1)

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.

• Coma

Official Coding Guidelines

Official source data — quoted verbatim from the CMS/NCHS Official Guidelines

Official source data — quoted verbatim from the CMS/NCHS Official Guidelines

Verbatim excerpts from the ICD-10-CM Official Guidelines for Coding and Reporting (CMS/NCHS) that govern this code.

Don’t confuse R40.20 with…

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

The codes most likely to be picked instead of R40.20 — 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.

• P91.5— 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 neonatal coma moves the case to P91.5; the two are not reported together unless documented as unrelated.

  Full comparison: R40.20 vs P91.5 →

• E08— 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 somnolence, stupor and coma in diabetes moves the case to E08; the two are not reported together unless documented as unrelated.

  Full comparison: R40.20 vs E08 →

• E13— 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 somnolence, stupor and coma in diabetes moves the case to E13; the two are not reported together unless documented as unrelated.

  Full comparison: R40.20 vs E13 →

• K72— 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 somnolence, stupor and coma in hepatic failure moves the case to K72; the two are not reported together unless documented as unrelated.

  Full comparison: R40.20 vs K72 →

• E15— 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 somnolence, stupor and coma in hypoglycemia (nondiabetic) moves the case to E15; the two are not reported together unless documented as unrelated.

  Full comparison: R40.20 vs E15 →

• F01— 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 symptoms and signs constituting part of a pattern of mental disorder adds F01; it is not part of this code and both may be reported when both are documented.

  Full comparison: R40.20 vs F01 →

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.

Decision Points

The directives on this code's own record, as a pre-claim checklist.

1. Sequencing: 3 Code First instructions — the underlying condition is sequenced before this code when present. See the Code First notes
2. 4 Excludes1 entries — codes named there are generally not reported together with this code (Guidelines I.A.12.a). See the Excludes1 notes
3. 1 Excludes2 entry — those conditions are not part of this code and may be reported additionally when documented. See the Excludes2 notes

Checklist rows are derived from this code's own official directives; the wording of each check is MedCoder editorial. The official notes themselves are in the sections each row links to.

Verify Before Coding

• MCC 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 R40.20 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 4 Excludes1 notes: R40.0 — Somnolence (via R40.2.-), R40.1 — Stupor (via R40.2.-), R41.82 — Altered mental status, unspecified (via R40.-), R55 — Syncope and collapse (via R40.2.-).

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

Referenced by 2 Use Additional Code instructions: T65.85 — Toxic effect of medetomidine (via R40.-), T67.0 — Heatstroke and sunstroke (via R40.-).

These codes instruct coders to additionally report this code when it applies.

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: MCC — Major 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 718 clinically related codes on its CMS exclusion list.

Named in the grouper logic of 4 MS-DRGs: DRG 080 (MDC 01), DRG 081 (MDC 01), DRG 791 (MDC 15), DRG 793 (MDC 15).

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

Clinical classification (AHRQ CCSR):NVS013 — Coma; stupor; and brain damage (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 CMS-HCC risk category (V28)

CMS maps these diagnoses to the same Hierarchical Condition Category (Coma, Brain Compression/Anoxic Damage) for risk-adjusted payment.

P91.4 — Neonatal cerebral depression, P91.5 — Neonatal coma, P91.60 — Hypoxic ischemic encephalopathy [HIE], unspecified, P91.61 — Mild hypoxic ischemic encephalopathy [HIE], P91.62 — Moderate hypoxic ischemic encephalopathy [HIE], P91.63 — Severe hypoxic ischemic encephalopathy [HIE], P91.811 — Neonatal encephalopathy in diseases classified elsewhere, P91.819 — Neonatal encephalopathy, unspecified, P91.88 — Other specified disturbances of cerebral status of newborn, P91.9 — Disturbance of cerebral status of newborn, unspecified, R40.2110 — Coma scale, eyes open, never, unspecified time, R40.2111 — Coma scale, eyes open, never, in the field [EMT or ambulance], R40.2112 — Coma scale, eyes open, never, at arrival to emergency department, R40.2113 — Coma scale, eyes open, never, at hospital admission, R40.2114 — Coma scale, eyes open, never, 24 hours or more after hospital admission, R40.2120 — Coma scale, eyes open, to pain, unspecified time, R40.2121 — Coma scale, eyes open, to pain, in the field [EMT or ambulance], R40.2122 — Coma scale, eyes open, to pain, at arrival to emergency department, R40.2123 — Coma scale, eyes open, to pain, at hospital admission, R40.2124 — Coma scale, eyes open, to pain, 24 hours or more after hospital admission, +40 more

Related risk categories

These categories interact through CMS's HCC hierarchy — one can suppress the other's risk-adjustment weight when both are present on a claim.

Major Head Injury with Loss of Consciousness > 1 Hour, Major Head Injury with Loss of Consciousness < 1 Hour or Unspecified, Chronic Liver Failure/End-Stage Liver Disorders

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Coma; stupor; and brain damage).

E09.641 — Drug or chemical induced diabetes mellitus with hypoglycemia with coma, E10.11 — Type 1 diabetes mellitus with ketoacidosis with coma, E10.641 — Type 1 diabetes mellitus with hypoglycemia with coma, E11.01 — Type 2 diabetes mellitus with hyperosmolarity with coma, E11.11 — Type 2 diabetes mellitus with ketoacidosis with coma, E11.641 — Type 2 diabetes mellitus with hypoglycemia with coma, E13.01 — Other specified diabetes mellitus with hyperosmolarity with coma, E13.11 — Other specified diabetes mellitus with ketoacidosis with coma, E13.641 — Other specified diabetes mellitus with hypoglycemia with coma, E15 — Nondiabetic hypoglycemic coma, G93.1 — Anoxic brain damage, not elsewhere classified, K70.41 — Alcoholic hepatic failure with coma, K71.11 — Toxic liver disease with hepatic necrosis, with coma, K72.01 — Acute and subacute hepatic failure with coma, K72.11 — Chronic hepatic failure with coma, K72.91 — Hepatic failure, unspecified with coma, R40.0 — Somnolence, R40.1 — Stupor, R40.2A — Nontraumatic coma due to underlying condition, R40.3 — Persistent vegetative state, +13 more

Same Index main term, other category

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

E03.5 — Myxedema coma (myxedematous), E15 — Nondiabetic hypoglycemic coma (hypoglycemic, nondiabetic), P91.5 — Neonatal coma (newborn)

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, Thyroid Stimulating Hormone (TSH)

Contextual Map

Every relationship of R40.20 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 R40.20 with these 6 related codes in Claim Check

Hierarchy

• R00-R99 — Chapter 18: Symptoms, Signs and Abnormal Clinical and Laboratory Findings, Not Elsewhere Classified (R00-R99) (R00-R99)[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• R40-R46 — Symptoms and signs involving cognition, perception, emotional state and behavior[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Referenced by Excludes1 notes

• R40.0 — Somnolence[Excludes1](via R40.2.-): “coma (R40.2-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• R40.1 — Stupor[Excludes1](via R40.2.-): “coma (R40.2-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• R41.82 — Altered mental status, unspecified[Excludes1](via R40.-): “altered level of consciousness (R40.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• R55 — Syncope and collapse[Excludes1](via R40.2.-): “unconsciousness NOS (R40.2-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Referenced by Use Additional Code instructions

• T65.85 — Toxic effect of medetomidine[Use Additional Code](via R40.-): “somnolence, stupor and coma (R40.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• T67.0 — Heatstroke and sunstroke[Use Additional Code](via R40.-): “coma and stupor (R40.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Clinical classification (CCSR)

• NVS013 — Coma; stupor; and brain damage[CCSR]— AHRQ CCSR for ICD-10-CM Diagnoses (HCUP)

Risk adjustment (CMS-HCC)

• HCC 202 — Coma, Brain Compression/Anoxic Damage [CMS-HCC]— CMS-HCC V28 · 2026

MS-DRG Grouper

• MCC — Major Complication or Comorbidity [MS-DRG severity]: “As a secondary diagnosis this code can raise the stay's MS-DRG severity tier (MCC).”— CMS MS-DRG Definitions Manual (Appendix C) · FY2026
• DRG 080 — NONTRAUMATIC STUPOR AND COMA WITH MCC[MS-DRG]: “NONTRAUMATIC STUPOR AND COMA WITH MCC (MDC 01)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026
• DRG 081 — NONTRAUMATIC STUPOR AND COMA WITHOUT MCC[MS-DRG]: “NONTRAUMATIC STUPOR AND COMA WITHOUT MCC (MDC 01)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026
• DRG 791 — PREMATURITY WITH MAJOR PROBLEMS[MS-DRG]: “PREMATURITY WITH MAJOR PROBLEMS (MDC 15)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026
• DRG 793 — FULL TERM NEONATE WITH MAJOR PROBLEMS[MS-DRG]: “FULL TERM NEONATE WITH MAJOR PROBLEMS (MDC 15)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026

MDC crossing

• MDC 01 — Diseases and Disorders of the Nervous System[MDC crossing]: “Diseases and Disorders of the Nervous 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. 8,892 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026
• MDC 15 — Newborns and Other Neonates with Conditions Originating in Perinatal Period[MDC crossing]: “Newborns and Other Neonates with Conditions Originating in Perinatal Period — 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.”— CMS MS-DRG Definitions Manual · FY2026

Index entries

• Coma[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes (40)

• R40 — Somnolence, stupor and coma[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• R40.0 — Somnolence[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• R40.1 — Stupor[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• R40.2 — Coma[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• R40.21 — Coma scale, eyes open[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• R40.211 — Coma scale, eyes open, never[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• R40.2110 — Coma scale, eyes open, never, unspecified time[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• R40.2111 — Coma scale, eyes open, never, in the field [EMT or ambulance][Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• and 32 more

Change history

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

Relevant guides

• Symptom Code or Confirmed Diagnosis: When an R Code Is Right, and When It Is Not →

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

Coding guidelines Official source data

ICD-10-CM Official Guidelines for Coding and Reporting (FY2026), quoted by section 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

Risk adjustment Official source data

2026 Mid-Year Final ICD-10 Mappings + Model Software (cms.gov/files/zip/2026-midyear-final-icd-10-mappings.zip, 2026-midyear-final-model-software.zip) — CMS-HCC V28, PY2026 mid-year final release 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 R40.20 in its code family, with their registry titles.

• R40 — Somnolence, stupor and coma
• R40.0 — Somnolence
• R40.1 — Stupor
• R40.2 — Coma
• R40.21 — Coma scale, eyes open
• R40.211 — Coma scale, eyes open, never
• R40.2110 — Coma scale, eyes open, never, unspecified time
• R40.2111 — Coma scale, eyes open, never, in the field [EMT or ambulance]
• R40.2112 — Coma scale, eyes open, never, at arrival to emergency department
• R40.2113 — Coma scale, eyes open, never, at hospital admission

View all codes in the R40 family