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T66.XXXD

T66.XXXD: Radiation sickness, unspecified, subsequent encounter

Billable / specific codeICD-10-CMPOA exempt

T66.XXXD is a billable, specific ICD-10-CM code for radiation sickness, unspecified, subsequent encounter. It is valid for submission on a claim.

Check T66.XXXD with the rest of the claim: free scrubber

7th character "D": subsequent encounter

The appropriate 7th character is to be added to code T66

A
initial encounter
D
subsequent encounter
S
sequela

Excludes1: never code together

These conditions cannot occur together. Billing both on the same encounter is a denial.

  • 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.-)

Excludes1 inherited from the categories above T66.XXXD

A category’s note binds every code beneath it.

Written on T66: Radiation sickness, unspecified

  • 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.-)

Risk adjustment

No CMS-HCC V28 category: this code does not change a RAF score.

Medicare coverage

T66.XXXD is named in 8 Medicare coverage policies: 8 listing it as supporting medical necessity. Which one applies depends on your Medicare contractor.

  • A52370Billing and Coding: Bevacizumab and biosimilars
  • A55315Billing and Coding: Proton Beam Therapy
  • A56612Billing and Coding: CT of the Head
  • A56625Billing and Coding: Echocardiography

Code history

Unchanged in every release from FY2024 to FY2027.

Other codes under T66

ICD-10-CMFY2027· effective October 1, 2026

Loaded directly from the CMS/NCHS ICD-10-CM public-domain release: see data sources and our editorial policy. If this page disagrees with the CMS tabular list, this page is wrong. Reference information for professional coders; not medical or billing advice.