T66 — Radiation sickness, unspecified
T66 is a non-billable header ICD-10-CM code for radiation sickness, unspecified. It cannot be billed on its own: choose one of the more specific child codes below. This code also requires a 7th character before it is complete.
This code requires a 7th character
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.
Risk adjustment
T66 does not map to an HCC and does not risk-adjust under CMS-HCC V28. That is normal — most ICD-10 codes do not. It still needs to be coded correctly; it just will not move a RAF score.
How T66 is indexed
Coders do not find codes by browsing the tabular list — they look them up in the alphabetic index, under the word the physician wrote. These are the index entries that lead here, so you can see which chart wordings map to T66.
- Irradiation effects, adverse
- Effect, adverse›infrared NOS(radiation) (rays)
- Effect, adverse›radiation NOS(diagnostic) (infrared) (natural source) (therapeutic) (ultraviolet) (X-ray)
- Effect, adverse›ultraviolet NOS(radiation) (rays)
- Radiation›effects NOS
- Radiation›sickness NOS
- Sickness›radiation
Code to one of these instead T66
3 child codes. Green means billable.
Questions about T66
- Is T66 a billable ICD-10-CM code?
- No. T66 is a non-billable header code. Code to a higher level of specificity using one of its child codes.
- Where does T66 sit in the tabular list?
- Injury, poisoning and certain other consequences of external causes (S00-T88), in the block Other and unspecified effects of external causes (T66-T78).
- What cannot be coded together with T66?
- T66 carries an Excludes1 note, which means the conditions it lists can never be coded together with it on the same encounter.