T66
Non-billableRadiation sickness, unspecified
Radiation sickness, unspecified
This is a header/category code. For billing purposes, use a more specific child code from the list below.
Coding Notes
Excludes 1
Codes that cannot be used together with this code (mutual exclusion)
Use Additional Code
Additional codes that should follow this code
7th Character Definitions
- A - initial encounter
- D - subsequent encounter
- S - sequela
Child Codes (3)
ICD-11 Equivalents(1)
ICD-11 Equivalents
View full mappingCorresponding ICD-11 codes from the WHO crosswalk mapping
Also Known As / Clinical Terms(1)
Frequently Asked Questions
What is the ICD-10 code for radiation sickness, unspecified?
The ICD-10-CM code for radiation sickness, unspecified is T66. The full clinical description is "Radiation sickness, unspecified". T66 is a non-billable header code. Use a more specific child code for billing purposes.
What does ICD-10 code T66 mean?
ICD-10-CM code T66 represents “Radiation sickness, unspecified”. It is classified under Chapter 19: Injury, Poisoning and Certain Other Consequences of External Causes and is a non-billable header code. Use a more specific child code for billing purposes.
Is T66 a billable code?
No, T66 is a non-billable header code. You need to use one of its more specific child codes for billing. There are 3 child codes under T66.
What chapter is T66 in?
T66 is in Chapter 19: Injury, Poisoning and Certain Other Consequences of External Causes (codes S00-T88).
What codes cannot be used with T66?
T66 has Excludes1 notes indicating codes that cannot be used together with it, including: birth trauma (P10-P15); obstetric trauma (O70-O71); specified adverse effects of radiation, such as:; and 6 more.
What are the subcategories under T66?
T66 has 3 child codes, including: T66.XXXA (Radiation sickness, unspecified, initial encounter), T66.XXXD (Radiation sickness, unspecified, subsequent encounter), T66.XXXS (Radiation sickness, unspecified, sequela).
Are additional codes required with T66?
Yes, when using T66, also report: any retained foreign body, if applicable (Z18.-).
What are the UMLS CUIs for T66?
T66 is linked to 1 UMLS Concept Unique Identifier: C2886219. The UMLS (Unified Medical Language System) integrates multiple biomedical vocabularies maintained by the U.S. National Library of Medicine.
How does T66 relate to ICF functioning codes?
ICF (International Classification of Functioning, Disability and Health) codes describe how conditions like radiation sickness, unspecified affect a person's functioning — body functions, activities, participation, and environmental factors. AutoICD provides ICF Core Sets for 12+ conditions and can map clinical text to ICF categories automatically. Browse the ICF directory to explore functioning codes.
What is the ICD-11 equivalent of T66?
T66 maps to the ICD-11 code: 8E61.0 (Radiation-induced brain injury).
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Includes SNOMED Clinical Terms® (SNOMED CT®) used by permission of SNOMED International. Includes content from the UMLS Metathesaurus, courtesy of the U.S. National Library of Medicine.