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T40.426A ICD-10-CM Code: Underdosing of tramadol, 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, Appendix B.

  • MS-DRG 951 — OTHER FACTORS INFLUENCING HEALTH STATUS (MDC 23)

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.

Official Registry Overview & Definition

Underdosing of tramadol, initial encounter is a billable ICD-10-CM diagnosis code (T40.426A).

Official Tabular Instructional Notes

Sequencing, inclusion, and exclusion notes published for T40.426A 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

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).

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)

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 Compared Codes

The official Excludes notes on T40.426A name these codes. Each comparison page covers when the two can — or must not — be reported together.

Change history

  • FY2021 — 2020-10-01
    Added to the code set
    Underdosing of tramadol, initial encounter
    FY2021 changes

Verify Before Coding

  • Principal-diagnosis restriction. The Medicare Code Editor lists this code as unacceptable as a principal diagnosis: it describes a circumstance influencing health status rather than a current illness or injury being treated. It is valid as a secondary diagnosis.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim.

Contextual Map

Every relationship of T40.426A 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.

Hierarchy

  • S00-T88 — Chapter 19: Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) (S00-T88) [Hierarchy]
  • T36-T50 — Poisoning by, adverse effects of and underdosing of drugs, medicaments and biological substances [Hierarchy]
  • T40-T41 — Analgesics & Antipyretics [Hierarchy]

Clinical classification (CCSR)

  • INJ029 — Underdosing of drugs and medicaments, initial encounter [CCSR]

Potential MS-DRG

  • DRG 951 — OTHER FACTORS INFLUENCING HEALTH STATUS [MS-DRG]: “OTHER FACTORS INFLUENCING HEALTH STATUS (MDC 23)”

MDC crossing · procedures (1235)

  • MDC 23 — Factors Influencing Health Status and Other Contacts with Health Services [MDC crossing]: “Factors Influencing Health Status and Other Contacts with Health Services — 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.”
  • F003GKZ — Communicative/Cognitive Integration Skills Assessment of Neurological System - Whole Body using Audiovisual Equipment [Same-MDC procedure]: “Communicative/Cognitive Integration Skills Assessment of Neurological System - Whole Body using Audiovisual Equipment — grouped in MDC 23, the procedure side of this code's crossing.” · check together
  • F003GMZ — Communicative/Cognitive Integration Skills Assessment of Neurological System - Whole Body using Augmentative / Alternative Communication Equipment [Same-MDC procedure]: “Communicative/Cognitive Integration Skills Assessment of Neurological System - Whole Body using Augmentative / Alternative Communication Equipment — grouped in MDC 23, the procedure side of this code's crossing.” · check together
  • F003GPZ — Communicative/Cognitive Integration Skills Assessment of Neurological System - Whole Body using Computer [Same-MDC procedure]: “Communicative/Cognitive Integration Skills Assessment of Neurological System - Whole Body using Computer — grouped in MDC 23, the procedure side of this code's crossing.” · check together
  • F003GYZ — Communicative/Cognitive Integration Skills Assessment of Neurological System - Whole Body using Other Equipment [Same-MDC procedure]: “Communicative/Cognitive Integration Skills Assessment of Neurological System - Whole Body using Other Equipment — grouped in MDC 23, the procedure side of this code's crossing.” · check together
  • F003GZZ — Communicative/Cognitive Integration Skills Assessment of Neurological System - Whole Body [Same-MDC procedure]: “Communicative/Cognitive Integration Skills Assessment of Neurological System - Whole Body — grouped in MDC 23, the procedure side of this code's crossing.” · check together
  • and 1230 more

Drugs & chemicals

  • Tramadol — Tramadol — Underdosing [Drug table]: “Tramadol (Underdosing)”

Nearest codes (40)

  • T40 — Poisoning by, adverse effect of and underdosing of narcotics and psychodysleptics [hallucinogens] [Sibling]
  • T40.421A — Poisoning by tramadol, accidental (unintentional), initial encounter [Sibling]
  • T40.421D — Poisoning by tramadol, accidental (unintentional), subsequent encounter [Sibling]
  • T40.421S — Poisoning by tramadol, accidental (unintentional), sequela [Sibling]
  • T40.422 — Poisoning by tramadol, intentional self-harm [Sibling]
  • T40.422A — Poisoning by tramadol, intentional self-harm, initial encounter [Sibling]
  • T40.422D — Poisoning by tramadol, intentional self-harm, subsequent encounter [Sibling]
  • T40.422S — Poisoning by tramadol, intentional self-harm, sequela [Sibling]
  • and 32 more

Change history

  • FY2021 — Added to the code set [Change history]

Relationships & Classification

Clinical classification (AHRQ CCSR):INJ029 — Underdosing of drugs and medicaments, initial encounter.

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Potential MS-DRG Relationships (FY2026)

Not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity.

Named in the grouper logic of 1 MS-DRG: DRG 951 (MDC 23).

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

Frequently Asked Questions (FAQ) & Clinical Guidance

Does T40.426A 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 T40.426A in its code family, with their registry titles.

  • T40.425 — Adverse effect of tramadol
  • T40.425A — Adverse effect of tramadol, initial encounter
  • T40.425D — Adverse effect of tramadol, subsequent encounter
  • T40.425S — Adverse effect of tramadol, sequela
  • T40.426 — Underdosing of tramadol
  • T40.426D — Underdosing of tramadol, subsequent encounter
  • T40.426S — Underdosing of tramadol, sequela
  • T40.49 — Poisoning by, adverse effect of and underdosing of other synthetic narcotics
  • T40.491 — Poisoning by other synthetic narcotics, accidental (unintentional)
  • T40.491A — Poisoning by other synthetic narcotics, accidental (unintentional), initial encounter

View all codes in the T40 family

Associated Substances (1)

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

  • Tramadol