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ICD-10-CM 2027 diagnosis code

T78.079AAnaphylactic reaction due to milk and dairy products, unspecified, initial encounter

✓ Billable / specificRequires 7th characterCC — complication/comorbidity

T78.079A is a valid, billable ICD-10-CM code for anaphylactic reaction due to milk and dairy products, unspecified, initial encounter. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.Short description: Anaphyl reaction due to milk and dairy products, unsp, init

Code last changed in FY2026 (effective October 1, 2025). Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About T78.079A

T78.079A is the ICD-10-CM diagnosis code for anaphylactic reaction due to milk and dairy products, unspecified, initial encounter. It belongs to category T78 (adverse effects, not elsewhere classified), block T66-T78 (other and unspecified effects of external causes) 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.

As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.

In MS-DRG v44.0, it is part of the grouping logic for DRG 915 (Allergic Reactions with MCC, relative weight 1.6558) and DRG 916 (Allergic Reactions without MCC, relative weight 0.6928), 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 FY2026, effective October 1, 2025.

7th character

Ainitial encounter

CC/MCC status for this injury by encounter: CC for A; Neither CC nor MCC for D, S.

Other encounter types for T78.079:

Notes that apply from higher levels

Instructions written at a parent level also apply to T78.079A.

› From T78 Adverse effects, not elsewhere classified
Excludes2
  • complications of surgical and medical care NEC (T80-T88)

Broader instructions also apply from T66-T78 Other and unspecified effects of external causes 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.

MDC 21 · Injuries, Poisonings and Toxic Effects of Drugs

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
  • FY2026 (effective 10/1/2025): Added
  • No changes since FY2026.

Common questions about T78.079A

Is T78.079A billable?

Yes. T78.079A 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 T78.079A 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 T78.079A be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict T78.079A as a principal diagnosis.

Is T78.079A a CC or MCC?

T78.079A is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.

What DRG does T78.079A group to?

T78.079A is used in the MS-DRG v44.0 logic for MS-DRG 915 (Allergic Reactions with MCC) and MS-DRG 916 (Allergic Reactions without MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.