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ICD-10/T40.1X1A

T40.1X1A ICD-10-CM Code: Poisoning by heroin, accidental (unintentional), initial encounter

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Inpatient Payment Groups (MS-DRG)

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v43.0 (FY2026), Appendix B.

  • MS-DRG 917 — POISONING AND TOXIC EFFECTS OF DRUGS WITH MCC (MDC 21)
  • MS-DRG 918 — POISONING AND TOXIC EFFECTS OF DRUGS WITHOUT MCC (MDC 21)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Risk Adjustment (CMS-HCC)

Payment categories this diagnosis maps to under CMS-HCC V28, payment year 2026.

  • HCC 137 — Drug Use Disorder, Moderate/Severe, or Drug Use with Non-Psychotic Complications (supersedes HCC 138, HCC 139)

Risk scores depend on the enrollee's full accepted diagnosis set and segment; a category mapping alone does not determine payment.

Code Set: Valid FY2026 and FY2027. FY2026 took effect October 1, 2025.

Official Registry Overview & Definition

Poisoning by heroin, accidental (unintentional), initial encounter is a billable ICD-10-CM diagnosis code (T40.1X1A).

Official Tabular Instructional Notes

Sequencing, inclusion, and exclusion notes published for T40.1X1A in the official ICD-10-CM tabular list.

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

Inclusion Terms

Alternative terms the tabular list files under this code.

  • Poisoning by heroin NOS

Excludes1 — Not Coded Here

Conditions that can never be reported with this code; the two are mutually exclusive.

  • toxic reaction to local anesthesia in pregnancy (O29.3-)

Excludes2 — Not Included Here

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

  • drug dependence and related mental and behavioral disorders due to psychoactive substance use (F10.-F19.-)
  • abuse and dependence of psychoactive substances (F10-F19)
  • abuse of non-dependence-producing substances (F55.-)
  • immunodeficiency due to drugs (D84.821)
  • drug reaction and poisoning affecting newborn (P00-P96)
  • pathological drug intoxication (inebriation) (F10-F19)

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)

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)
  • underdosing of medication regimen (Z91.12-, Z91.13-)

Frequently Asked Questions (FAQ) & Clinical Guidance

Does T40.1X1A require a 7th character?

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

Nearest Codes in This Family

Official ICD-10-CM classifications closest to T40.1X1A in its code family, with their registry titles.

  • T40.0X6D — Underdosing of opium, subsequent encounter
  • T40.0X6S — Underdosing of opium, sequela
  • T40.1 — Poisoning by and adverse effect of heroin
  • T40.1X — Poisoning by and adverse effect of heroin
  • T40.1X1 — Poisoning by heroin, accidental (unintentional)
  • T40.1X1D — Poisoning by heroin, accidental (unintentional), subsequent encounter
  • T40.1X1S — Poisoning by heroin, accidental (unintentional), sequela
  • T40.1X2 — Poisoning by heroin, intentional self-harm
  • T40.1X2A — Poisoning by heroin, intentional self-harm, initial encounter
  • T40.1X2D — Poisoning by heroin, intentional self-harm, subsequent encounter

View all codes in the T40 family

Associated Substances (4)

Substances from the official ICD-10-CM Table of Drugs and Chemicals that map to this code.

  • Acetomorphine
  • Diacetylmorphine
  • Diamorphine
  • Heroin