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T65 ICD-10-CM Code: Toxic effect of other and unspecified substances

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Billing Status: NO. This is a non-billable ICD-10-CM code: report a more specific billable code beneath it.

Coding at a Glance

7th character
Required — characters A · D · S
Tabular directives
1 Excludes1 · 4 use-additional codes

Category · FY2027A non-billable heading in the tabular list: report a more specific code beneath it.

What you need to know

Source: CMS/NCHS Official ICD-10-CM tabular notes, quoted. From the CMS/NCHS tabular list for the release in force. A note the category or block publishes applies to this code too; the Instructions section marks which is which.

Use additional codeReport with this code when documented
  • code(s):
  • for all associated manifestations of toxic effect, such as: respiratory conditions due to external agents (J60-J70)
  • personal history of foreign body fully removed (Z87.821)
  • to identify any retained foreign body, if applicable (Z18.-)
Excludes1Never report with this code
  • contact with and (suspected) exposure to toxic substances (Z77.-)

Most relevant related codes MedCoder-derived

Read off the official notes above and this code’s own position in the tabular list. Which to report is a documentation question; Compare shows the two side by side.

CompareCheck ClaimView Related Codes

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for T65 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2027Effective: October 1, 2026

Trace:FY2027 changesChange historyRelease, file and checksum

Notes without a marker are published on T65 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 T51-T65

Use Additional Code

Supplementary codes the tabular list directs you to add.

  • Use additional code(s):
  • for all associated manifestations of toxic effect, such as: respiratory conditions due to external agents (J60-J70)
  • personal history of foreign body fully removed (Z87.821)
  • to identify any retained foreign body, if applicable (Z18.-)

Source: inherited from T51-T65

7th Character Guide

"The appropriate 7th character is to be added to each code from category T65"

  • 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

T65.0X1A, T65.0X1D, T65.0X1S, T65.0X2A, T65.0X2D, T65.0X2S, T65.0X3A, T65.0X3D

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 T65

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

Before you code T65

  1. T65 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).

    ReviewT65.0, T65.1, T65.2, T65.3, T65.4, T65.5, T65.6, T65.8, T65.9

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

  2. Unspecified does not mean incorrect. When the record gives no greater specificity, T65 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).

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

  3. A 7th character is required in this family. Confirm the documented encounter: initial (active treatment), subsequent (healing or recovery phase), or sequela. T65 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 →

  4. Confirm whether the documentation describes a poisoning, an adverse effect of a correctly prescribed and administered drug, an underdosing, or a toxic effect, and the intent where the record states it: the Table of Drugs and Chemicals separates these by column, and the sequencing differs for each. Poisoning, adverse effect and underdosing guidelines (Guidelines I.C.19.e).

    See the Table of Drugs and Chemicals entries · Guide: Poisoning vs adverse effect vs underdosing →

  5. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with T65. 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 T65?
    Yes → Select that code and continue the checks below on its own page.
    No → T65 cannot be reported as written; query for the specificity its subcategory needs.

    ReviewT65.0, T65.1, T65.2, T65.3, T65.4, T65.5, T65.6, T65.8, T65.9

  2. Does the record document the detail a more specific sibling code needs?
    Yes → Review the specific siblings in this subcategory.
    No → Continue — T65 is appropriate when the documentation goes no further.
  3. Does the documentation support a condition named in T65’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.

    ReviewZ77

  4. 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 T65. Then work the Use Additional Code note, and 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 conditions the Use Additional Code note names
Reported with this code when documented; a conditional instruction (“if applicable”, “if known”) applies only when the record supports it.
External cause, place and activity
For the external cause codes reported with the injury or poisoning, where documented (Guidelines I.C.20.a).
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 T65(1 note)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with T65: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareZ77

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

  • Use Additional Code — after identifying T65(4 notes)

    Coding workflow: Check whether the documentation supports the additional code(s) the note names, and report them with T65 when it does. Where the instruction is conditional (“if applicable”, “if known”), it applies only when the record documents the condition.

    ReviewZ87.821, Z18

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

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 subcategory for a sibling that names the missing detail.

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).

Documentation: Both the condition T65 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).

ReviewZ77

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).

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.

Don’t confuse T65 with…

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

The codes most likely to be picked instead of T65 — 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.

  • Z77— 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 contact with and (suspected) exposure to toxic substances moves the case to Z77; the two are not reported together unless documented as unrelated.

    Full comparison: T65 vs Z77 →

  • T65.0X1A— Encounter relationship (Review)

    Same underlying diagnosis, different encounter phase.

    The same diagnosis at a different phase of care; one encounter takes one 7th character.

    What moves you there: Documentation of a initial encounter moves the case to T65.0X1A.

    Full comparison: T65 vs T65.0X1A →

  • T65.0X1D— Encounter relationship (Review)

    Same underlying diagnosis, different encounter phase.

    The same diagnosis at a different phase of care; one encounter takes one 7th character.

    What moves you there: Documentation of a subsequent encounter moves the case to T65.0X1D.

    Full comparison: T65 vs T65.0X1D →

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.

Coding context

Guidelines, coding notes, decision aids, relationships (with MS-DRG and CCSR classification), hierarchy, HCC, coverage and the context map: what a coder reaches for after the core. Each section names whether it is official source data, a MedCoder-derived relationship or MedCoder editorial.

Code Overview

Toxic effect of other and unspecified substances is a non-billable ICD-10-CM category code (T65). 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.

Official Coding 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.

Chapter 19: Injury, poisoning, and certain other consequences of external causes (S00-T88)

e. Adverse Effects, Poisoning, Underdosing and Toxic Effects Codes in categories T36-T65 are combination codes that include the substance that was taken as well as the intent. No additional external cause code is required for poisonings, toxic effects, adverse effects and underdosing codes.

Chapter 19: Injury, poisoning, and certain other consequences of external causes (S00-T88)

(d) Toxic Effects W hen a harmful substance is ingested or comes in contact with a person, this is classified as a toxic effect. The toxic effect codes are in categories T51-T65. When coding a toxic effect, assign the toxic effect code first, followed by codes for all associated manifestations of the toxic effect.

Decision Points

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

  1. A 7th character applies in this family. Confirm the documented encounter matches the character assigned. See the official 7th-character definitions and this code’s variants
  2. 4 Use Additional Code instructions — report the named additional code(s) when the documentation supports them. See the Use Additional Code notes
  3. 1 Excludes1 entry — codes named there are generally not reported together with this code (Guidelines I.A.12.a). See the Excludes1 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

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-derived relationships — computed from published CMS and AHRQ datasets

Other codes that name T65 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 11 Excludes2 notes across 2 chapters: T80 — Complications following infusion, transfusion and therapeutic injection, T80-T88 — Complications of surgical and medical care, not elsewhere classified (T80-T88), T81 — Complications of procedures, not elsewhere classified, T82 — Complications of cardiac and vascular prosthetic devices, implants and grafts, T83 — Complications of genitourinary prosthetic devices, implants and grafts, T84 — Complications of internal orthopedic prosthetic devices, implants and grafts, T85 — Complications of other internal prosthetic devices, implants and grafts, T86 — Complications of transplanted organs and tissue, T87 — Complications peculiar to reattachment and amputation, T88 — Other complications of surgical and medical care, not elsewhere classified, Z77 — Other contact with and (suspected) exposures hazardous to health.

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

Referenced by 68 Code First instructions across 14 chapters: D61.2 — Aplastic anemia due to other external agents, D64.2 — Secondary sideroblastic anemia due to drugs and toxins, E03.2 — Hypothyroidism due to medicaments and other exogenous substances, E09 — Drug or chemical induced diabetes mellitus, F02 — Dementia in other diseases classified elsewhere, G21.2 — Secondary parkinsonism due to other external agents, G62.2 — Polyneuropathy due to other toxic agents, G70.1 — Toxic myoneural disorders, G72.2 — Myopathy due to other toxic agents, G92.8 — Other toxic encephalopathy, G92.9 — Unspecified toxic encephalopathy, H10.21 — Acute toxic conjunctivitis, H35.38 — Toxic maculopathy, H46.3 — Toxic optic neuropathy, H91.0 — Ototoxic hearing loss, I42.7 — Cardiomyopathy due to drug and external agent, J68 — Respiratory conditions due to inhalation of chemicals, gases, fumes and vapors, J69.1 — Pneumonitis due to inhalation of oils and essences, J69.8 — Pneumonitis due to inhalation of other solids and liquids, J70.8 — Respiratory conditions due to other specified external agents, +48 more.

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.

Contextual Map

Every relationship of T65 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 T65 with these 24 related codes in Claim Check

Hierarchy

Excludes1

Use Additional Code (13)

  • J60 — Coalworker's pneumoconiosis[Use Additional Code]: “for all associated manifestations of toxic effect, such as: respiratory conditions due to external agents (J60-J70)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027
  • J61 — Pneumoconiosis due to asbestos and other mineral fibers[Use Additional Code]: “for all associated manifestations of toxic effect, such as: respiratory conditions due to external agents (J60-J70)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027
  • J62 — Pneumoconiosis due to dust containing silica[Use Additional Code]: “for all associated manifestations of toxic effect, such as: respiratory conditions due to external agents (J60-J70)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027
  • J63 — Pneumoconiosis due to other inorganic dusts[Use Additional Code]: “for all associated manifestations of toxic effect, such as: respiratory conditions due to external agents (J60-J70)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027
  • J64 — Unspecified pneumoconiosis[Use Additional Code]: “for all associated manifestations of toxic effect, such as: respiratory conditions due to external agents (J60-J70)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027
  • J65 — Pneumoconiosis associated with tuberculosis[Use Additional Code]: “for all associated manifestations of toxic effect, such as: respiratory conditions due to external agents (J60-J70)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027
  • J66 — Airway disease due to specific organic dust[Use Additional Code]: “for all associated manifestations of toxic effect, such as: respiratory conditions due to external agents (J60-J70)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027
  • J67 — Hypersensitivity pneumonitis due to organic dust[Use Additional Code]: “for all associated manifestations of toxic effect, such as: respiratory conditions due to external agents (J60-J70)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027
  • and 5 more

Referenced by Excludes2 notes (11)

Referenced by Code First instructions (68)

Nearest codes (280)

Change history

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

Reference

Index terms and tables, published questions and FAQ, every source behind this page with its release and checksum, the date-of-service check and the complete change history.

Common coding questions

MedCoder editorial

Can T65 be billed directly?

No. T65 (Toxic effect of other and unspecified substances) is a non-billable ICD-10-CM category code. A more specific billable subcode must be selected based on clinical documentation.

Does T65 require a 7th character?

Yes. The appropriate 7th character is to be added to each code from category T65; 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 FY2027 tabular list, index and tables, effective October 1, 2026 Release, file and checksum · Publisher’s page
Coding guidelines Official source data
ICD-10-CM Official Guidelines for Coding and Reporting (FY2027), quoted by section Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v44.0 (October 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-derived 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 editorial 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.

Current data releases:ICD-10-CM FY2027 · ICD-10-PCS FY2027 · HCPCS October 2026 · MS-DRG v44 · Medicare Code Editor v44.0 · NCCI PTP Q4 2026 · MUE Q4 2026 · NCD code lists 2026-01 · LCD export September 28, 2026 · All releases and sources

Labels on this page: Official source data · MedCoder-derived relationship · MedCoder editorial explanation. How to read the labels · All data sources and release dates · CMS coding rules

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. "T65 — Toxic effect of other and unspecified substances." ICD-10-CM FY2027. https://medcoder.ai/icd10/code/t65-toxic-effect-of-other-and-unspecified-substances

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Toxic effect of other and unspecified substances

No changes since FY2016 — additions, deletions, description changes and billable-status changes are tracked through FY2027, 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 T65 in its code family, with their registry titles.