T66
⚠ Non-billable
Radiation sickness, unspecified
ICD-10-CM · FY2026 · Injury, Poisoning and Certain Other Consequences of External Causes
Code
T66
System
ICD-10-CM
Billable
No — use specific code
Effective
FY2026
Chapter
Injury, Poisoning and Certain Other Consequences of External Causes
Source
CMS / CDC NCHS
⚠ Verify before billing. Confirm against the current CMS/NCHS ICD-10-CM files and your payer's rules before claims submission.
Official coding notes
From CMS's ICD-10-CM Tabular List.
Excludes1 — never code together
- 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
- The appropriate 7th character is to be added to code T66
Frequently asked questions
What is ICD-10 code T66?
ICD-10-CM code T66 represents Radiation sickness, unspecified. It is a non-billable header code requiring a more specific subcategory in the Injury, Poisoning and Certain Other Consequences of External Causes chapter, effective October 1, 2025 – September 30, 2026.
Is T66 billable?
No. T66 is a non-billable header. Select a more specific subcategory for claims submission.
What chapter is T66 in?
T66 belongs to the Injury, Poisoning and Certain Other Consequences of External Causes chapter (S00–T88) of ICD-10-CM.
Related codes in the T66 category
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