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T40 ICD-10-CM Code: Poisoning by, adverse effect of and underdosing of narcotics and psychodysleptics [hallucinogens]

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
4 inclusion terms · 1 Excludes1 · 6 Excludes2 · 4 use-additional codes · 7 code-first instructions

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for T40 in the official ICD-10-CM tabular list, quoted as published.

Notes without a marker are published on T40 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.

  • adverse effect of correct substance properly administered
  • poisoning by overdose of substance
  • poisoning by wrong substance given or taken in error
  • underdosing by (inadvertently) (deliberately) taking less substance than prescribed or instructed

Source: inherited from T36-T50

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 T36-T50

Excludes2 — Not Included Here

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

Code First

Underlying conditions that must be sequenced before this code.

  • Code first, for adverse effects, the nature of the adverse effect, such as:
  • adverse effect NOS (T88.7)
  • aspirin gastritis (K29.-)
  • blood disorders (D56-D76)
  • contact dermatitis (L23-L25)
  • dermatitis due to substances taken internally (L27.-)
  • nephropathy (N14.0-N14.2)
    N14.0-N14.2: N14.0, N14.1, N14.11, N14.19, N14.2

Source: inherited from T36-T50

Use Additional Code

Supplementary codes the tabular list directs you to add.

  • Use additional code(s) to specify:
  • manifestations of poisoning
  • underdosing or failure in dosage during medical and surgical care (Y63.6, Y63.8-Y63.9)
    Y63.8-Y63.9: Y63.8, Y63.9
  • underdosing of medication regimen (Z91.12-, Z91.13-)

Source: inherited from T36-T50

7th Character Guide

"The appropriate 7th character is to be added to each code from category T40"

  • 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

T40-T41, T40.0X1A, T40.0X1D, T40.0X1S, T40.0X2A, T40.0X2D, T40.0X2S, T40.0X3A

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 T40

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

Before you code T40

  1. T40 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).

    ReviewT40.0, T40.1, T40.2, T40.3, T40.4, T40.5, T40.6, T40.7, T40.8, T40.9

    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. T40 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. 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 →

  4. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with T40. 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 T40?
    Yes → Select that code and continue the checks below on its own page.
    No → T40 cannot be reported as written; query for the specificity its subcategory needs.

    ReviewT40.0, T40.1, T40.2, T40.3, T40.4, T40.5, T40.6, T40.7, T40.8, T40.9

  2. Does the documentation support a condition named in T40’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.

    ReviewO29.3

  3. Is the underlying (etiologic) condition the Code First note names documented?
    Yes → Sequence the underlying condition first, then T40.
    No → Continue; do not add an underlying condition the record does not document.

    ReviewT88.7, K29, L27

  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 T40. 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 underlying (etiologic) condition
Named in the Code First note; sequenced before this code when documented (Guidelines I.A.13).
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).

Official instructions as workflow

  • Excludes1 — check before selecting T40(1 note)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with T40: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareO29.3

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

  • Excludes2 — not part of T40(6 notes)

    Coding workflow: The conditions named in this note are not included in T40. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

    CompareF10, F19, F55, D84.821

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

  • Code First — sequencing check(7 notes)

    Coding workflow: Check whether the underlying or etiologic condition the note names is documented. When it is, sequence it before T40. Do not add an underlying condition the record does not document.

    ReviewT88.7, K29, L27

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

  • Use Additional Code — after identifying T40(4 notes)

    Coding workflow: Check whether the documentation supports the additional code(s) the note names, and report them with T40 when it does. Where the instruction is conditional (“if applicable”, “if known”), it applies only when the record documents the condition.

    ReviewY63.6, Z91.12, Z91.13

    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: Both the condition T40 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).

ReviewO29.3

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: The underlying condition the Code First note names is documented alongside this condition.

Coding question: How are the two sequenced?

Path: Review the Code First note.

Reason: The underlying condition is sequenced first and the manifestation follows (Guidelines I.A.13).

ReviewT88.7, K29, L27

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

Poisoning by, adverse effect of and underdosing of narcotics and psychodysleptics [hallucinogens] is a non-billable ICD-10-CM category code (T40). 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.

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. Sequencing: 7 Code First instructions — the underlying condition is sequenced before this code when present. See the Code First notes
  3. 4 Use Additional Code instructions — report the named additional code(s) when the documentation supports them. See the Use Additional Code notes
  4. 1 Excludes1 entry — codes named there are generally not reported together with this code (Guidelines I.A.12.a). See the Excludes1 notes
  5. 6 Excludes2 entries — 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

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 T40 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 1 Excludes1 note: T41 — Poisoning by, adverse effect of and underdosing of anesthetics and therapeutic gases.

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

Referenced by 14 Excludes2 notes across 3 chapters: F11.2 — Opioid dependence, T41.3 — Poisoning by, adverse effect of and underdosing of local anesthetics, T43 — Poisoning by, adverse effect of and underdosing of psychotropic drugs, not elsewhere classified, 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, Y63 — Failure in dosage during surgical and medical care.

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

Referenced by 20 Code First instructions across 13 chapters: 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, G92.8 — Other toxic encephalopathy, G92.9 — Unspecified toxic encephalopathy, H35.38 — Toxic maculopathy, H91.0 — Ototoxic hearing loss, I42.7 — Cardiomyopathy due to drug and external agent, K22.1 — Ulcer of esophagus, K71 — Toxic liver disease, L53.0 — Toxic erythema, M34.2 — Systemic sclerosis induced by drug and chemical, N14 — Drug- and heavy-metal-induced tubulo-interstitial and tubular conditions, P58.4 — Neonatal jaundice due to drugs or toxins transmitted from mother or given to newborn, Z91.12 — Patient's intentional underdosing of medication regimen, Z91.13 — Patient's unintentional underdosing of medication regimen, Z91.14 — Patient's other noncompliance with medication regimen, Z91.A2 — Caregiver's intentional underdosing of patient's medication regimen, Z91.A3 — Caregiver's unintentional underdosing of patient's medication regimen.

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.

Referenced by 99 Use Additional Code instructions across 15 chapters: D46 — Myelodysplastic syndromes, D52.1 — Drug-induced folate deficiency anemia, D59.0 — Drug-induced autoimmune hemolytic anemia, D59.2 — Drug-induced nonautoimmune hemolytic anemia, D59.39 — Other hemolytic-uremic syndrome, D61.1 — Drug-induced aplastic anemia, D64.2 — Secondary sideroblastic anemia due to drugs and toxins, D70.2 — Other drug-induced agranulocytosis, D72.12 — Drug rash with eosinophilia and systemic symptoms syndrome, D84.821 — Immunodeficiency due to drugs, D89.3 — Immune reconstitution syndrome, E03.2 — Hypothyroidism due to medicaments and other exogenous substances, E06.4 — Drug-induced thyroiditis, E09 — Drug or chemical induced diabetes mellitus, E16.0 — Drug-induced hypoglycemia without coma, E22.1 — Hyperprolactinemia, E23.1 — Drug-induced hypopituitarism, E24.2 — Drug-induced Cushing's syndrome, E25.8 — Other adrenogenital disorders, E27.3 — Drug-induced adrenocortical insufficiency, +79 more.

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

Referenced by 1 Code Also instruction: Z91.1 — Patient's noncompliance with medical treatment and regimen.

These codes suggest coding this condition alongside when both are present.

Contextual Map

Every relationship of T40 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 T40 with these 24 related codes in Claim Check

Hierarchy

Excludes1

Excludes2 (12)

Code First (32)

Use Additional Code

Referenced by Excludes1 notes

Referenced by Excludes2 notes (14)

Referenced by Code First instructions (20)

Referenced by Use Additional Code instructions (99)

  • D46 — Myelodysplastic syndromes[Use Additional Code]: “code for adverse effect, if applicable, to identify drug (T36-T50 with fifth or sixth character 5)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
  • D52.1 — Drug-induced folate deficiency anemia[Use Additional Code]: “code for adverse effect, if applicable, to identify drug (T36-T50 with fifth or sixth character 5)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
  • D59.0 — Drug-induced autoimmune hemolytic anemia[Use Additional Code]: “code for adverse effect, if applicable, to identify drug (T36-T50 with fifth or sixth character 5)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
  • D59.2 — Drug-induced nonautoimmune hemolytic anemia[Use Additional Code]: “code for adverse effect, if applicable, to identify drug (T36-T50 with fifth or sixth character 5)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
  • D59.39 — Other hemolytic-uremic syndrome[Use Additional Code]: “code, if applicable, for adverse effect to identify drug (T36-T50 with fifth or sixth character 5)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
  • D61.1 — Drug-induced aplastic anemia[Use Additional Code]: “code for adverse effect, if applicable, to identify drug (T36-T50 with fifth or sixth character 5)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
  • D64.2 — Secondary sideroblastic anemia due to drugs and toxins[Use Additional Code]: “code for adverse effect, if applicable, to identify drug (T36-T50 with fifth or sixth character 5)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
  • D70.2 — Other drug-induced agranulocytosis[Use Additional Code]: “code for adverse effect, if applicable, to identify drug (T36-T50 with fifth or sixth character 5)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
  • and 91 more

Referenced by Code Also instructions

Nearest codes (369)

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 T40 be billed directly?

No. T40 (Poisoning by, adverse effect of and underdosing of narcotics and psychodysleptics [hallucinogens]) is a non-billable ICD-10-CM category code. A more specific billable subcode must be selected based on clinical documentation.

Does T40 require a 7th character?

Yes. The appropriate 7th character is to be added to each code from category T40; 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

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Poisoning by, adverse effect of and underdosing of narcotics and psychodysleptics [hallucinogens]

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 T40 in its code family, with their registry titles.