ICD-10-CM 2027 diagnosis code

T78Adverse effects, not elsewhere classified

Not billable — use a more specific code

T78 is a header code, so it can't be reported by itself. Choose one of the 6 more specific codes beneath it.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About T78

T78 is the ICD-10-CM diagnosis code for adverse effects, not elsewhere classified. It belongs to block T66-T78 (other and unspecified effects of external causes) and chapter 19 (injury, poisoning and certain other consequences of external causes). It is a header code, so it can't be reported by itself; one of its 6 subcodes must be used instead.

To report this condition, pick the subcode that matches the documentation: T78.0 (food), T78.1 (classified), T78.2 (unspecified), T78.3 (edema), T78.4 (allergy) and T78.8 (classified).

The conditions in its Excludes2 note aren't part of T78, but may be coded alongside it if the patient has both: complications of surgical and medical care NEC (T80-T88).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Specific codes under T78

Coding notes

Excludes2Not included here — may be reported together if both conditions exist

complications of surgical and medical care NEC (T80-T88)

Notes that apply from higher levels

Instructions written at a parent level also apply to T78.

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.

Codes whose notes reference T78

T75Excludes1

Code history

2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027

FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
No changes since FY2016.

Common questions about T78

Is T78 billable?: No. T78 is a header code. Report one of its more specific subcodes instead.