2027 ICD-10-CM Diagnosis Code T59.7X2AToxic effect of carbon dioxide, intentional self-harm, initial encounter
T59.7X2A is a billable ICD-10-CM diagnosis code for toxic effect of carbon dioxide, intentional self-harm, 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under External cause codes: intent of injury, self-harm; External cause codes: poisoning by non-drug; and Suicidal ideation/attempt/intentional self-harm.
For Medicare Advantage risk adjustment, T59.7X2A maps to CMS-HCC Category 155 (Major Depression, Moderate or Severe, without Psychosis) under the V28 model, adding a risk factor of about 0.299 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
T59.7X2A 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.
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Toxic effect of other gases, fumes and vapors (T59). 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 T59.7X2A: its own notes plus those printed at T59, block T51-T65, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
- chlorofluorocarbons (T53.5)
- contact with and (suspected) exposure to toxic substances (Z77.-)
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.
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.
- When no intent is indicated code to accidental. Undetermined intent is only for use when there is specific documentation in the record that the intent of the toxic effect cannot be determined.
- 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 T59
- 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 T59.7X2A, 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.
Patient EducationClinical
Poisoning
A poison is any substance that is harmful to your body. You might swallow it, inhale it, inject it, or absorb it through your skin. Any substance can be poisonous if too much is taken. Poisons can include:
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T59.7X2A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T59.7X2AOverview
Is T59.7X2A (Toxic effect of carbon dioxide, intentional self-harm) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report toxic effect of carbon dioxide, intentional self-harm, initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What does the 7th character A in T59.7X2A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for toxic effect of carbon dioxide, intentional self-harm, such as an emergency visit or first evaluation.
What MS-DRG does T59.7X2A group to?
When toxic effect of carbon dioxide, intentional self-harm, 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 T59.7X2A be reported with T53.5?
Not as a rule. The Excludes1 note at T59, which applies to T59.7X2A, lists "chlorofluorocarbons (T53.5)". 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 is the ICD-9 equivalent of T59.7X2A?
Under the General Equivalence Mappings, toxic effect of carbon dioxide, intentional self-harm, initial encounter converts to ICD-9-CM 987.8 (toxic eff gas/vapor NEC) and E952.8 (poison-gas/vapor NEC). The mapping is approximate, so confirm the match fits the documentation.
What HCC is T59.7X2A?
T59.7X2A (toxic effect of carbon dioxide, intentional self-harm, initial encounter) maps to CMS-HCC Category 155 (Major Depression, Moderate or Severe, without Psychosis), commonly written as HCC 155, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 59 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 132.
Does T59.7X2A risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, T59.7X2A adds a risk adjustment factor of about 0.299 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.108 to 0.316 depending on the payment segment). A more severe related category (HCC 151, HCC 152, HCC 153, and HCC 154) supersedes it when both are reported. See the full factor table on the HCC 155 category page.
