T66.XXXS – Radiation sickness, unspecified, sequela

ICD-10-CM 2027 diagnosis code · Other and unspecified effects of external causes

Billable code

ICD-10-CM code T66.XXXS
Code
T66.XXXS (claims format: T66XXXS)
Description
Radiation sickness, unspecified, sequela
Billable
Yes – valid for HIPAA-covered transactions
Valid for
Dates of service October 1, 2026 – September 30, 2027 (FY2027)
Chapter
19. Injury, poisoning and certain other consequences of external causes (S00-T88)
Block
T66-T78 Other and unspecified effects of external causes
Parent codes
T66

7th character values

Codes in this category need a 7th character to describe the encounter or episode of care.

CharacterMeaning
Ainitial encounter
Dsubsequent encounter
Ssequela

Notes inherited from parent codes

Instructional notes at a category or block level apply to every code below it.

T66 – Radiation sickness, unspecified

Excludes1 (not coded here):
  • 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.-)
7th character note:
  • The appropriate 7th character is to be added to code T66

Block T66-T78

Code also:
  • , 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-)

Related codes in T66

Frequently asked questions

What is ICD-10 code T66.XXXS?

T66.XXXS is the ICD-10-CM code for radiation sickness, unspecified, sequela, in the block T66-T78 (Other and unspecified effects of external causes).

Is T66.XXXS a billable code?

Yes. T66.XXXS is a billable/specific code that can be used to indicate a diagnosis for reimbursement purposes.

What category does T66.XXXS belong to?

It belongs to category T66 – Radiation sickness, unspecified.

Source: CDC/NCHS ICD-10-CM FY2027 code files, tabular list and index. Reference only – code assignment must follow the official ICD-10-CM guidelines and documentation in the medical record.