T66 Radiation sickness, unspecified

The ICD-10-CM code for Radiation sickness, unspecified is T66 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Chapter

19: Injury, poisoning and certain other consequences of external causes (S00-T88)

Section

T66-T78: Other and unspecified effects of external causes (T66-T78)

Category T66

1 code (1 billable)

FY2026 Status

Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to T66:

• Irradiation effects, adverse
• Radiation › sickness NOS
• Sickness › radiation
• Effect, adverse › infrared (radiation) (rays) NOS
• Radiation › effects NOS
• Effect, adverse › radiation (diagnostic) (infrared) (natural source) (therapeutic) (ultraviolet) (X-ray) NOS
• Effect, adverse › ultraviolet (radiation) (rays) NOS

Official Coding Guidelines

Sequence blood vessel/nerve injury first (fragment)

injury is to the blood vessels or nerves, that injury should be sequenced first.

Do not assign injury codes for iatrogenic injuries; code complication

3) Iatrogenic injuries Injury codes from Chapter 19 should not be assigned for injuries that occur during, or as a result of, a medical intervention. Assign the appropriate complication code(s).

Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026

References

• CMS — ICD-10-CM Official Code Set and Guidelines, FY2026
• CDC/NCHS — ICD-10-CM Files and Browser Tool