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 2026. The section is organized into the 11 code ranges listed below.
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
ICD-10 codes T66-T78 cover various unique medical effects resulting from external causes such as radiation, heat, cold, air pressure, asphyxiation, deprivation, abuse, exploitation, and allergic reactions. These codes specifically classify illnesses and injuries related to these external factors, including detailed encounters and sequelae stages.
This range includes T66 for radiation sickness, also known as acute radiation syndrome and radiation-induced anemia, allowing coding for initial, subsequent, or sequela encounters. Codes T67 address heat-related conditions like heatstroke, sunstroke, exertional heatstroke (also called hyperthermia), heat syncope, cramps, and heat exhaustion types. The hypothermia category (T68) and related codes (T69) cover cold-induced effects like immersion hand/foot and chilblains. Barotrauma from air or water pressure is classified under T70, including otitic and sinus barotrauma and decompression sickness (Caisson disease).
Asphyxiation codes (T71) detail mechanical threats to breathing such as smothering, plastic bag suffocation, hanging, and trapping in confined spaces, with distinctions for accidental, self-harm, assault, or undetermined intent. Effects of deprivation (T73) include starvation, water deprivation, and exhaustion due to exposure or exertion.
Adult and child abuse, neglect, maltreatment, and exploitation are classified under T74 (confirmed) and T76 (suspected), specifying types such as physical, sexual, psychological, financial abuse, and forced labor or sexual exploitation. The codes differentiate adult and child victims across initial, subsequent, and sequela encounters.
Lastly, T78 covers diverse adverse effects not elsewhere classified, including anaphylactic reactions to foods (e.g., peanuts, shellfish, milk), other allergic and anaphylactic responses, angioneurotic edema, unspecified allergies, and other adverse effects such as electrocution and lightning injury. These codes aid in precise documentation of allergic emergencies, with multiple synonyms like food-dependent exercise-induced anaphylaxis and latex protein-induced angioedema for clarity.
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 2026. 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 2026 ICD-10-CM Tabular List and order file, effective October 1, 2025 through September 30, 2026.
