ICDcodes.org
FY2027

T66 — Radiation sickness, unspecified

Not billable

Is T66 billable?

No — T66 is a non-billable header code. T66 groups more specific codes and cannot be submitted on a claim. A valid ICD-10-CM code must be reported at the highest level of specificity available in its branch. Select one of the 3 billable codes beneath T66.

T66 at a glance

CodeT66
DescriptionRadiation sickness, unspecified
BillableNo — header code
Code setICD-10-CM FY2027
Valid for encountersOctober 1, 2026 – September 30, 2027

How is T66 listed in the Alphabetic Index?

These are the routes through the Alphabetic Index that lead to T66. They show the wording a clinician may have documented, which often differs from the Tabular description.

  • Irradiation effects, adverse
  • Effect, adverse › infraredNOS
  • Effect, adverse › radiationNOS
  • Effect, adverse › ultravioletNOS
  • Radiation › effects NOS
  • Radiation › sickness NOS
  • Sickness › radiation

Excludes1 — never code together

The conditions below can never be reported together with T66 on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.

  • 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.-)

Use additional code — inherited from Chapter 19

Report an additional code alongside T66 to fully describe the condition. T66 is sequenced first.

  • code to identify any retained foreign body, if applicable (Z18.-)

Excludes2 — not included here — inherited from Chapter 19

The conditions below are not part of T66, but a patient may have both at the same time. When documentation supports it, T66 and the excluded code may both be reported.

  • birth trauma (P10-P15)
  • obstetric trauma (O70-O71)

Code also — inherited from T66-T78

Two codes may be needed to describe the condition fully. Whether T66 is sequenced first depends on the reason for the encounter.

  • , 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-)

What codes fall under T66? (3)

How long has T66 existed?

T66 has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.

Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.

Which codes are confused with T66?

ICD-10-CM declares these codes mutually exclusive with T66 — exactly one of each pair can be correct for a given encounter.