T66.XXXA: Radiation sickness, unspecified, initial encounter

T66.XXXA, radiation sickness, unspecified, initial encounter, is listed as a covered diagnosis in 6 Medicare billing and coding articles that apply to 39 HCPCS Level II codes, including J0461 (Injection, atropine sulfate, 0.01 mg), J0153 (Injection, adenosine, 1 mg (not to be used to report any…), J1250 (Injection, dobutamine hydrochloride, per 250 mg). The articles come from 3 Medicare contractors. A listed diagnosis supports medical necessity only; coverage still depends on the LCD's criteria and on documentation in the medical record.

HCPCS Level II codes with T66.XXXA as a covered diagnosis

CodeDescriptionMedicare coverageDMEPOS fee 2026 (state range)Articles listing it
J0461Injection, atropine sulfate, 0.01 mgSpecial coverage instructions apply—3
J0153Injection, adenosine, 1 mg (not to be used to report any adenosine phosphate compounds)Special coverage instructions apply—3
J1250Injection, dobutamine hydrochloride, per 250 mgSpecial coverage instructions apply—3
J0280Injection, aminophyllin, up to 250 mgSpecial coverage instructions apply—3
J1245Injection, dipyridamole, per 10 mgSpecial coverage instructions apply—3
A9700Supply of injectable contrast material for use in echocardiography, per studySpecial coverage instructions apply—3
G0340Image-guided robotic linear accelerator-based stereotactic radiosurgery, delivery including collimator changes and custom plugging, fractionated treatment, all lesions, per session, second through fifth sessions, maximum five sessions per course of treatmentCarrier judgment—1
G0339Image-guided robotic linear accelerator-based stereotactic radiosurgery, complete course of therapy in one session or first session of fractionated treatmentCarrier judgment—1
G0563Stereotactic body radiation therapy, treatment delivery, per fraction to 1 or more lesions, including image guidance and real-time positron emissions-based delivery adjustments to 1 or more lesions, entire course not to exceed 5 fractionsCarrier judgment—1
J2785Injection, regadenoson, 0.1 mgCarrier judgment—2
Q9957Injection, perflutren lipid microspheres, per mlCarrier judgment—2
Q9956Injection, octafluoropropane microspheres, per mlCarrier judgment—2
C8921Transthoracic echocardiography with contrast, or without contrast followed by with contrast, for congenital cardiac anomalies; completeSpecial coverage instructions apply—2
C8922Transthoracic echocardiography with contrast, or without contrast followed by with contrast, for congenital cardiac anomalies; follow-up or limited studySpecial coverage instructions apply—2
C8923Transthoracic echocardiography with contrast, or without contrast followed by with contrast, real-time with image documentation (2d), includes m-mode recording, when performed, complete, without spectral or color doppler echocardiographySpecial coverage instructions apply—2
C8924Transthoracic echocardiography with contrast, or without contrast followed by with contrast, real-time with image documentation (2d), includes m-mode recording, when performed, follow-up or limited studySpecial coverage instructions apply—2
C8928Transthoracic echocardiography with contrast, or without contrast followed by with contrast, real-time with image documentation (2d), includes m-mode recording, when performed, during rest and cardiovascular stress test using treadmill, bicycle exercise and/or pharmacologically induced stress, with interpretation and reportSpecial coverage instructions apply—2
C8929Transthoracic echocardiography with contrast, or without contrast followed by with contrast, real-time with image documentation (2d), includes m-mode recording, when performed, complete, with spectral doppler echocardiography, and with color flow doppler echocardiographySpecial coverage instructions apply—2
C8930Transthoracic echocardiography, with contrast, or without contrast followed by with contrast, real-time with image documentation (2d), includes m-mode recording, when performed, during rest and cardiovascular stress test using treadmill, bicycle exercise and/or pharmacologically induced stress, with interpretation and report; including performance of continuous electrocardiographic monitoring, with physician supervisionSpecial coverage instructions apply—2
Q9955Injection, perflexane lipid microspheres, per mlCarrier judgment—2
Q5129Injection, bevacizumab-adcd (vegzelma), biosimilar, 10 mgCarrier judgment—1
Q5126Injection, bevacizumab-maly, biosimilar, (alymsys), 10 mgCarrier judgment—1
Q5118Injection, bevacizumab-bvzr, biosimilar, (zirabev), 10 mgCarrier judgment—1
Q5107Injection, bevacizumab-awwb, biosimilar, (mvasi), 10 mgSpecial coverage instructions apply—1
J9035Injection, bevacizumab, 10 mgCarrier judgment—1

14 more codes are listed. See every code with payment by region in Caduvo.

Medicare policy articles listing T66.XXXA

A diagnosis listed as covered in a billing and coding article supports medical necessity for the article's codes; it does not guarantee payment. Coverage depends on the LCD's criteria, the contractor's jurisdiction and documentation in the medical record.

Frequently asked questions

Does Medicare cover T66.XXXA (Radiation sickness, unspecified, initial encounter)?

Medicare covers items and services, not diagnoses. 6 Medicare billing and coding articles list T66.XXXA as a covered diagnosis for 39 HCPCS Level II codes: the diagnosis can support medical necessity for those codes, but payment still depends on the LCD's coverage criteria and the medical record.

Which HCPCS codes can be billed with ICD-10 T66.XXXA?

The Level II codes from the policies most specific to this diagnosis are J0461 (Injection, atropine sulfate, 0.01 mg, 3 articles); J0153 (Injection, adenosine, 1 mg (not to be used to report any…, 3 articles); J1250 (Injection, dobutamine hydrochloride, per 250 mg, 3 articles); J0280 (Injection, aminophyllin, up to 250 mg, 3 articles); J1245 (Injection, dipyridamole, per 10 mg, 3 articles). Code choice depends on the item supplied; check each code's descriptor.

Which Medicare policy articles list T66.XXXA?

A56874 (Billing and Coding: Stereotactic Radiation Therapy: Stereotactic Radiosurgery (SRS) and Stereotactic Body Radiation Therapy (SBRT)); A52370 (Billing and Coding: Bevacizumab and biosimilars); A57306 (Billing and Coding: Transthoracic Echocardiography (TTE)), and 3 more articles.

What is ICD-10-CM code T66.XXXA?

T66.XXXA is the ICD-10-CM code for radiation sickness, unspecified, initial encounter, in category T66 (Radiation sickness, unspecified), chapter 19: Injury, poisoning and other consequences of external causes.

Next steps

Sources: CMS Medicare Coverage Database billing and coding articles (covered ICD-10 code lists and HCPCS links); ICD-10-CM FY2026; CMS HCPCS Level II release October 2026; CMS DMEPOS fee schedule 2026 (non-rural state fees). Not billing or legal advice.

Chapter 19: Injury, poisoning and other consequences of external causes · All diagnoses · HCPCS lookup