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W55 ICD-10-CM Code: Contact with other mammals

Billing Status: NO. This is a clinician non-billable / parent hierarchy grouping in the ICD-10-CM system.

Coding at a Glance

7th character
Required — characters A · D · S
Tabular directives
1 inclusion term · 5 Excludes1

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for W55 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 W55 itself; “inherited from” names the category or block whose note applies here.

Includes

Conditions the official ICD-10-CM tabular list includes under this code.

  • contact with saliva, feces or urine of mammal

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).

7th Character Guide

"The appropriate 7th character is to be added to each code from category W55"

  • A — initial encounter
  • D — subsequent encounter
  • S — sequela

How the encounter character is assigned. “Initial encounter” means the patient is receiving active treatment for the condition — it is not limited to the first visit, and a different or new provider giving active treatment still assigns it. “Subsequent encounter” covers care during the healing or recovery phase after active treatment. “Sequela” is for complications or conditions that arise as a direct result of the original condition.

ICD-10-CM Official Guidelines for Coding and Reporting, Section I.C.19.a (paraphrased by MedCoder).

Variant codes in this family

W55.01XA, W55.01XD, W55.01XS, W55.03XA, W55.03XD, W55.03XS, W55.09XA, W55.09XD

Character meanings are CMS's official 7th-character extensions for this family, as carried in each variant code's official description; variant codes are registry rows. The explanation of how the encounter character is assigned is MedCoder editorial, distinct from the official content above it.

Coder workflow for W55

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

Before you code W55

  1. W55 is not reportable as written. Select the more specific code beneath it that the documentation supports. Codes are reported to the highest level of specificity the classification provides (Guidelines I.B.2).

    ReviewW55.0, W55.1, W55.2, W55.3, W55.4, W55.5, W55.8

    See the relationships section · Guide: How to choose an ICD-10-CM code →

  2. A 7th character is required in this family. Confirm the documented encounter: initial (active treatment), subsequent (healing or recovery phase), or sequela. W55 is not valid without one. “Initial” means active treatment, not the first visit (Guidelines I.C.19.a).

    See the 7th Character Guide · Guide: 7th characters: initial, subsequent, sequela →

  3. W55’s title joins a condition with an associated condition or complication. Confirm each component is documented. Where the classification presumes the link through the “with” convention, only a provider statement that the conditions are unrelated defeats it. A combination code is assigned only when it fully identifies the documented conditions; a required second code for the stage, type or manifestation is still reported when the notes ask for it (Guidelines I.B.9, I.A.15).

    Guide: Combination codes →

  4. An external cause code is reported in addition to the code for the injury or condition, never as the principal or first-listed diagnosis. Confirm the cause, intent, place of occurrence, activity and status where the record documents them, and assign the 7th character that matches the injury code. External cause coding guidelines (Guidelines I.C.20.a).

  5. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with W55. 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 one of the more specific codes beneath W55?
    Yes → Select that code and continue the checks below on its own page.
    No → W55 cannot be reported as written; query for the specificity its subcategory needs.

    ReviewW55.0, W55.1, W55.2, W55.3, W55.4, W55.5, W55.8

  2. Does the documentation support a condition named in W55’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.

    ReviewW54, W53, W56, T63

  3. Is the encounter phase documented — active treatment, healing or recovery, or a sequela?
    Yes → Assign the matching 7th character; the variant codes are in the 7th Character Guide.
    No → The code is invalid without its 7th character — query for the missing element.

Consider W55. 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).
Encounter type
Active treatment, healing or recovery phase, or sequela — the basis of the 7th character (Guidelines I.C.19.a).
The associated condition or complication
Whether the associated condition the title names is documented; the “with” convention presumes some links, and a provider statement that the conditions are unrelated defeats it (Guidelines I.A.15).

Official instructions as workflow

  • Excludes1 — check before selecting W55(5 notes)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with W55: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareW54, W53, W56, T63

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

Coding decision scenarios

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

Documentation: Both the condition W55 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).

ReviewW54, W53, W56, T63

Documentation: The patient returns during the healing or recovery phase after active treatment of the same condition.

Coding question: Which 7th character applies?

Path: Review the official 7th-character definitions for this family in the 7th Character Guide.

Reason: “Initial encounter” means active treatment, not the first visit; care during recovery takes “subsequent encounter”, and a complication arising from the original condition takes “sequela” (Guidelines I.C.19.a).

Documentation: Only one of the components this code’s title joins is documented.

Coding question: Is W55 supported?

Path: Review the code for the documented component on its own.

Reason: A combination code is assigned only when it fully identifies the documented conditions; otherwise the documented component takes its own code (Guidelines I.B.9).

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

Contact with other mammals is a non-billable ICD-10-CM category code (W55). A more specific billable subcode must be selected for claims submission.

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

Verify Before Coding

  • Not billable as written — a more specific code is required: W55.01XA, W55.01XD, W55.01XS, W55.03XA, W55.03XD.
  • Requires a 7th character. "The appropriate 7th character is to be added to each code from category W55" Options: W55.01XA, W55.01XD, W55.01XS, W55.03XA, W55.03XD, W55.03XS
  • Principal-diagnosis restriction. External cause of morbidity codes (V, W, X and Y) describe the circumstance that caused an injury, not the condition treated. The Medicare Code Editor rejects them as a principal diagnosis; sequence the injury or condition first and report this code as secondary.

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 W55 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 27 Excludes1 notes: W20 — Struck by thrown, projected or falling object, W20-W49 — Exposure to inanimate mechanical forces (W20-W49), W21 — Striking against or struck by sports equipment, W22 — Striking against or struck by other objects, W23 — Caught, crushed, jammed or pinched in or between objects, W24 — Contact with lifting and transmission devices, not elsewhere classified, W25 — Contact with sharp glass, W26 — Contact with other sharp objects, W27 — Contact with nonpowered hand tool, W28 — Contact with powered lawn mower, W29 — Contact with other powered hand tools and household machinery, W30 — Contact with agricultural machinery, W31 — Contact with other and unspecified machinery, W32 — Accidental handgun discharge and malfunction, W33 — Accidental rifle, shotgun and larger firearm discharge and malfunction, W34 — Accidental discharge and malfunction from other and unspecified firearms and guns, W35 — Explosion and rupture of boiler, W36 — Explosion and rupture of gas cylinder, W37 — Explosion and rupture of pressurized tire, pipe or hose, W38 — Explosion and rupture of other specified pressurized devices, +7 more.

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

Contextual Map

Every relationship of W55 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 W55 with these 12 related codes in Claim Check

Hierarchy

Excludes1

Referenced by Excludes1 notes (27)

Nearest codes (91)

Change history

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

Common coding questions

Can W55 be billed directly?

No. W55 (Contact with other mammals) is a non-billable ICD-10-CM category code. A more specific billable subcode must be selected based on clinical documentation.

Does W55 require a 7th character?

Yes. The appropriate 7th character is to be added to each code from category W55; A: initial encounter; D: subsequent encounter; S: sequela.

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
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. "W55 — Contact with other mammals." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/w55-contact-with-other-mammals

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Contact with other mammals

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 W55 in its code family, with their registry titles.