2027 ICD-10-CM Diagnosis Code T78Adverse effects, not elsewhere classified

ICD-10-CM Codes›S00–T88›T66-T78›T78

ICD-10-CM T78
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

T78 is a non-billable ICD-10-CM category code for adverse effects, not elsewhere classified, so it cannot be submitted on claims. Use a more specific code from this category instead, such as T78.00XA, T78.00XD, T78.00XS, and T78.01XA.

Code Identity

ICD-10-CM Code
T78
Billable Status
No — Non-Billable Category
Code Describes
Adverse effects, not elsewhere classified
Short Description
Adverse effects, not elsewhere classified
Same as the full description in the CMS dataset.
Chapter
T66-T78
Other and unspecified effects of external causes

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT66-T78Other and unspecified effects of external causes
CategoryT78Adverse effects, not elsewhere classified
This CodeT78Adverse effects, not elsewhere classified

Specific Coding for Adverse effects, not elsewhere classifiedOverview

Non-specific codes like T78 require more characters. Use one of these billable codes instead:

  • T78.0 for Anaphylactic reaction due to food

  • T78.00 for Anaphylactic reaction due to unspecified food

  • T78.01 for Anaphylactic reaction due to peanuts

  • T78.02 for Anaphylactic reaction due to shellfish (crustaceans)

  • T78.03 for Anaphylactic reaction due to other fish

  • T78.04 for Anaphylactic reaction due to fruits and vegetables

  • T78.05 for Anaphylactic reaction due to tree nuts and seeds

  • T78.06 for Anaphylactic reaction due to food additives

  • T78.07 for Anaphylactic reaction due to milk and dairy products

  • T78.08 for Anaphylactic reaction due to eggs

  • T78.09 for Anaphylactic reaction due to other food products

  • T78.1 for Other adverse food reactions, not elsewhere classified

  • T78.11 for Other adverse food reactions due to milk and dairy products

  • T78.12 for Other adverse food reaction due to eggs

  • T78.19 for Other adverse food reactions, not elsewhere classified

  • T78.2 for Anaphylactic shock, unspecified

  • T78.3 for Angioneurotic edema

  • T78.4 for Other and unspecified allergy

  • T78.40 for Allergy, unspecified

  • T78.41 for Arthus phenomenon

  • T78.49 for Other allergy

  • T78.8 for Other adverse effects, not elsewhere classified

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Adverse effects, not elsewhere classified (T78). 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 T78: its own notes plus those printed at block T66-T78 and Chapter 19. A note printed at a category, block or chapter applies to every code under it.

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.

On T78 itself
  • complications of surgical and medical care NEC (T80-T88)
From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • code to identify any retained foreign body, if applicable (Z18.-)

Code Also

A second code may be needed to fully describe the condition; the note gives no sequencing direction.

From Block T66-T78 Other and unspecified effects of external causes applies to 456 codes
  • if applicable, place of occurrence, such as:
  • highway rest stop (Y92.523)
  • school (private) (public) (state) as the place of occurrence of the external cause (Y92.21-)
  • service areas as the place of occurrence of the external cause (Y92.52-)
  • single-family non-institutional (private) house as the place of occurrence of the external cause (Y92.01-)
  • transport vehicle as the place of occurrence of the external cause (Y92.81-)

Notes

General instructions on how these codes are used.

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • 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 T78
Values for category T78 Encounter: Initial, Subsequent, Sequela
  • Ainitial encounter
  • 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 T78, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming T78: they are not reported together with it, unless the two conditions are unrelated.

  • T75 Other and unspecified effects of other external causes
    adverse effects NEC (T78.-)

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About T78Overview

What is the ICD-10 code for adverse effects, not elsewhere classified?

T78 is the ICD-10-CM category for adverse effects, not elsewhere classified, but it is a non-billable header: claims need a more specific code from this category, listed on this page.

Is T78 (Adverse effects, not elsewhere classified) a billable code?

No. This is a category header that groups the codes for adverse effects, not elsewhere classified, and headers cannot be submitted on claims. Claims for adverse effects, not elsewhere classified need a more specific code from this category, such as T78.00XA, T78.00XD, and T78.00XS.