2027 ICD-10-CM Diagnosis Code T40.0X1APoisoning by opium, accidental (unintentional), initial encounter
T40.0X1A is a billable ICD-10-CM diagnosis code for poisoning by opium, accidental (unintentional), initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 917 through 918. Coders also document this condition as accidental poisoning by opium. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under External cause codes: intent of injury, accidental/unintentional; External cause codes: poisoning by drug; and Opioid-related disorders.
For Medicare Advantage risk adjustment, T40.0X1A maps to CMS-HCC Category 137 (Drug Use Disorder, Moderate/Severe, or Drug Use with Non-Psychotic Complications) under the V28 model, adding a risk factor of about 0.424 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
T40.0X1A maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Accidental poisoning by opium
- Poisoning by opium
- Poisoning by opium alkaloid
Coding GuidelinesGuidance
When coding a poisoning or reaction to the improper use of a medication (e.g., overdose, wrong substance given or taken in error, wrong route of administration), first assign the appropriate code from categories T36-T50. The poisoning codes have an associated intent as their 5th or 6th character (accidental, intentional self-harm, assault and undetermined). If the intent of the poisoning is unknown or unspecified, code the intent as accidental intent. The undetermined intent is only for use if the documentation in the record specifies that the intent cannot be determined. Use additional code(s) for all manifestations of poisonings.
The appropriate 7th character is to be added to each code from block Poisoning by, adverse effect of and underdosing of narcotics and psychodysleptics [hallucinogens] (T40). Use the following options for the applicable episode of care:
- A - initial encounter
- D - subsequent encounter
- S - sequela
Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027, published by CMS and the National Center for Health Statistics.
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to T40.0X1A: its own notes plus those printed at T40, block T36-T50, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- 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: the excluded code is never reported together with this one, unless the two conditions are unrelated.
- toxic reaction to local anesthesia in pregnancy (O29.3-)
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
Code First
The underlying condition named in the note is sequenced before this code.
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code to identify any retained foreign body, if applicable (Z18.-)
Notes
General instructions on how these codes are used.
- Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
- The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.
7th Character
Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.
- The appropriate 7th character is to be added to each code from category T40
- Ainitial encounter this code
- Dsubsequent encounter
- Ssequela
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name T40.0X1A, its category, or a range that includes it.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Table of Drugs and ChemicalsClinical
Substances in the Table of Drugs and Chemicals that reference this code family. Always confirm in the Tabular List before coding.
| Substance | Accidental | Self-harm | Assault | Undetermined | Adverse Effect | Underdosing |
|---|---|---|---|---|---|---|
| Laudanum | T40.0X1 | T40.0X2 | T40.0X3 | T40.0X4 | T40.0X5 | T40.0X6 |
| Opium alkaloids (total) | T40.0X1 | T40.0X2 | T40.0X3 | T40.0X4 | T40.0X5 | T40.0X6 |
| Opium alkaloids (total)::standardized powdered | T40.0X1 | T40.0X2 | T40.0X3 | T40.0X4 | T40.0X5 | T40.0X6 |
| Opium alkaloids (total)::tincture (camphorated) | T40.0X1 | T40.0X2 | T40.0X3 | T40.0X4 | T40.0X5 | T40.0X6 |
| Pantopon | T40.0X1 | T40.0X2 | T40.0X3 | T40.0X4 | T40.0X5 | T40.0X6 |
| Papaveretum | T40.0X1 | T40.0X2 | T40.0X3 | T40.0X4 | T40.0X5 | T40.0X6 |
| Paregoric | T40.0X1 | T40.0X2 | T40.0X3 | T40.0X4 | T40.0X5 | T40.0X6 |
Convert T40.0X1A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T40.0X1AOverview
What is the ICD-10 code for poisoning by opium, accidental (unintentional), initial encounter?
The ICD-10-CM code for poisoning by opium, accidental (unintentional), initial encounter is T40.0X1A (sometimes written as T400X1A). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is T40.0X1A (Poisoning by opium, accidental (unintentional)) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report poisoning by opium, accidental (unintentional), initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What does the 7th character A in T40.0X1A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for poisoning by opium, accidental (unintentional), such as an emergency visit or first evaluation.
What MS-DRG does T40.0X1A group to?
When poisoning by opium, accidental (unintentional), initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 918, 917, with relative weights from 0.8716 to 1.5698 depending on complications. Higher weights mean higher Medicare reimbursement.
Can T40.0X1A be reported with a code from O29.3?
Not as a rule. The Excludes1 note at block T36-T50, which applies to T40.0X1A, lists "toxic reaction to local anesthesia in pregnancy (O29.3-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
What HCC is T40.0X1A?
T40.0X1A (poisoning by opium, accidental (unintentional), initial encounter) maps to CMS-HCC Category 137 (Drug Use Disorder, Moderate/Severe, or Drug Use with Non-Psychotic Complications), commonly written as HCC 137, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 55 under the retired V24 model. It also maps in the ESRD (V24) model. It does not map to any RxHCC in the Part D prescription drug model.
Does T40.0X1A risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, T40.0X1A adds a risk adjustment factor of about 0.424 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.297 to 0.502 depending on the payment segment). A more severe related category (HCC 135 and HCC 136) supersedes it when both are reported. See the full factor table on the HCC 137 category page.
