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ICD-10-CM 2027 diagnosis code

T45.AX3APoisoning by immune checkpoint inhibitors and immunostimulant drugs, assault, initial encounter

✓ Billable / specificRequires 7th character

T45.AX3A is a valid, billable ICD-10-CM code for poisoning by immune checkpoint inhibitors and immunostimulant drugs, assault, initial encounter. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.Short description: Poisn by immune chkpt inhibtr/immunostim drugs, asslt, init

Code last changed in FY2025 (effective October 1, 2024). Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About T45.AX3A

T45.AX3A is the ICD-10-CM diagnosis code for poisoning by immune checkpoint inhibitors and immunostimulant drugs, assault, initial encounter. It belongs to category T45 (poisoning by, adverse effect of and underdosing of primarily systemic and hematological agents, not elsewhere classified), block T36-T50 (poisoning by, adverse effects of and underdosing of drugs, medicaments and biological substances) and chapter 19 (injury, poisoning and certain other consequences of external causes). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

The 7th character "A" means initial encounter: use it while the patient is receiving active treatment for the condition.

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 917 (Poisoning and Toxic Effects of Drugs with MCC, relative weight 1.57) and DRG 918 (Poisoning and Toxic Effects of Drugs without MCC, relative weight 0.872), in MDC 21 (Injuries, Poisonings and Toxic Effects of Drugs), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It was added in FY2025, effective October 1, 2024.

7th character

Ainitial encounter

Other encounter types for T45.AX3:

Notes that apply from higher levels

Instructions written at a parent level also apply to T45.AX3A.

› From T45.A Poisoning by, adverse effect of and underdosing of immune checkpoint inhibitors and immunostimulant drugs
Excludes1
  • poisoning by, adverse effect of and underdosing of antineoplastic and immunosuppressive drug (T45.1)

Broader instructions also apply from T36-T50 Poisoning by, adverse effects of and underdosing of drugs, medicaments and biological substances and Chapter 19: Injury, poisoning and certain other consequences of external causes.

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2025 (effective 10/1/2024): Added
  • No changes since FY2025.

Common questions about T45.AX3A

Is T45.AX3A billable?

Yes. T45.AX3A is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

What does the "A" at the end of T45.AX3A mean?

It is the 7th character for initial encounter. Per the official guidelines, use it while the patient is receiving active treatment for the condition.

Can T45.AX3A be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict T45.AX3A as a principal diagnosis.

Is T45.AX3A a CC or MCC?

No. T45.AX3A is neither a CC nor an MCC under MS-DRG v44.0.

What DRG does T45.AX3A group to?

T45.AX3A is used in the MS-DRG v44.0 logic for MS-DRG 917 (Poisoning and Toxic Effects of Drugs with MCC) and MS-DRG 918 (Poisoning and Toxic Effects of Drugs without MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.