T66: Radiation sickness, unspecified
Codes under T66 (Radiation sickness, unspecified). A ✓ marks a billable (fully specified) code; category codes without a ✓ are not billable on their own.
| Code | Description | Billable |
|---|---|---|
| T66.XXXA | Radiation sickness, unspecified, initial encounter | ✓ |
| T66.XXXA | Radiation sickness, unspecified, initial encounter | ✓ |
| T66.XXXD | Radiation sickness, unspecified, subsequent encounter | ✓ |
| T66.XXXD | Radiation sickness, unspecified, subsequent encounter | ✓ |
| T66.XXXS | Radiation sickness, unspecified, sequela | ✓ |
| T66.XXXS | Radiation sickness, unspecified, sequela | ✓ |
Frequently asked questions
What is ICD-10-CM code T66?
T66 is an ICD-10-CM category covering Radiation sickness, unspecified. It contains 6 more specific diagnosis codes, 6 of which are billable.
Is T66 a billable code?
No — T66 is a category header and isn't billable on its own. Code to the highest level of specificity using one of its subcodes (for example T66.XXXA — Radiation sickness, unspecified, initial encounter). 6 of the 6 codes under T66 are billable.
What codes fall under T66?
T66 includes T66.XXXA, T66.XXXA, T66.XXXD, T66.XXXD, T66.XXXS, plus 1 more. See the full list with descriptions and billable status above.
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Informational only, not coding or medical advice. Verify against the official ICD-10-CM (FY2026) and your payer's guidelines.
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