Other and unspecified effects of external causes (T66-T78) ICD-10-CM
The T66–T78 section covers other and unspecified effects of external causes with 660 ICD-10-CM diagnosis codes, of which 456 are billable in fiscal year 2027. The section is organized into the 11 code ranges listed below.
Code Also
A "code also" note instructs that two codes may be required to fully describe a condition, but this note does not provide sequencing direction.
- , 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
Code Ranges in This Section 11 ranges · 660 codes
The info icon previews the code ranges inside each row and its instructional notations from the official Tabular List.
About the T66–T78 Code Range
Radiation sickness, heat and cold effects, pressure-related conditions, and interrupted breathing appear alongside deprivation, maltreatment, and other effects of external causes.
T66 identifies unspecified radiation sickness. T67 separates heat and light effects such as heatstroke, cramps, and exhaustion. T68 identifies hypothermia, or lower than normal body temperature. T69 groups other reduced-temperature effects. T70 separates air and water pressure effects by type, including ear, sinus, and high-altitude effects.
T71 separates asphyxiation by its cause. T73 distinguishes starvation, water deprivation, and exhaustion from exposure or exertion. Maltreatment codes distinguish confirmed cases in T74 from suspected cases in T76, then separate types such as neglect and physical abuse.
T75 includes lightning, vibration, motion sickness, and other external effects. T78 separates adverse effects such as food reactions and allergies. Each category lists a seventh character for an initial encounter, subsequent encounter, or sequela.
Questions About This Page
How many codes are in the T66-T78 range?
The T66-T78 range contains 660 ICD-10-CM diagnosis codes in FY 2027. 456 of them are billable, and the rest are category headers that organize the section.
What conditions does T66-T78 cover?
The range covers other and unspecified effects of external causes. The code ranges listed above break it into groups of related conditions, and each one links to its own page with the full code list.
Related References
Source: CMS FY 2027 ICD-10-CM Tabular List and order file, effective October 1, 2026 through September 30, 2027.
