T66 ICD-10-CM Code: Radiation sickness, unspecified
A clear reference for the official code description, hierarchy, and related coding information from the FY 2027 U.S. release.
Official description
T66Radiation sickness, unspecified
ICD-10-CM diagnosis code · United States clinical modification
Where T66 sits
- 1
Chapter 19
Injury, poisoning and certain other consequences of external causes (S00-T88)
- 2
Section
Other and unspecified effects of external causes (T66-T78)
- 3
Category T66
Radiation sickness, unspecified
- 4
Code T66
Radiation sickness, unspecified
Codes under T66
T66 is a non-billable category. Choose the child code that best matches the documented diagnosis.
Notes for this code
Inclusion terms
No inclusion terms are listed for T66.
Code first
No “code first” instruction is listed for T66.
Use additional code
No “use additional code” instruction is listed for T66.
Excludes1
Conditions that should not be reported together with this code.
- specified adverse effects of radiation, such as:
- burns (T20-T31)
- leukemia (C91-C95)
- radiation gastroenteritis and colitis (K52.0)
- radiation pneumonitis (J70.0)
- radiation related disorders of the skin and subcutaneous tissue (L55-L59)
- sunburn (L55.-)
Excludes2
Conditions not included here that may be reported separately when present.
No Excludes2 note is listed for T66.
Source and release
- Data release
- U.S. ICD-10-CM · FY 2027
- Effective date
- Oct 1, 2026
- Publisher
- Vero Scribe Inc.
This reference is generated from Vero’s ICD-10-CM description, hierarchy, and code-note dataset. The visible content and structured data share that source.
Frequently asked questions
What does ICD-10-CM code T66 mean?
T66 is the FY 2027 U.S. ICD-10-CM code for “Radiation sickness, unspecified.”
Is T66 a billable or specific ICD-10-CM code?
No. T66 has more specific child codes in the FY 2027 reference data. Select the code that matches the documentation and confirm the active code set and payer requirements.
Where is T66 located in ICD-10-CM?
T66 is listed in Chapter 19, Injury, poisoning and certain other consequences of external causes (S00-T88), within Other and unspecified effects of external causes (T66-T78) (T66–T78), under category T66, Radiation sickness, unspecified.
What coding notes are listed for T66?
No inclusion terms are listed for T66 in this reference record. No code-first instruction is listed. Excludes1 notes: specified adverse effects of radiation, such as:; burns (T20-T31); leukemia (C91-C95); radiation gastroenteritis and colitis (K52.0); radiation pneumonitis (J70.0); radiation related disorders of the skin and subcutaneous tissue (L55-L59); sunburn (L55.-). No Excludes2 note is listed.