Z91.A28: Caregiver's intentional underdosing of medication regimen for other reason

Z91.A28, Caregiver's intentional underdosing of medication regimen for other reason, is listed as a covered diagnosis in 4 Medicare billing and coding articles that apply to 5 HCPCS Level II codes, including G0480 (Drug test(s), definitive, utilizing (1) drug…), G0483 (Drug test(s), definitive, utilizing (1) drug…), G0482 (Drug test(s), definitive, utilizing (1) drug…). The articles come from 4 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 Z91.A28 as a covered diagnosis

CodeDescriptionMedicare coverageDMEPOS fee 2026 (state range)Articles listing it
G0480Drug test(s), definitive, utilizing (1) drug identification methods able to identify individual drugs and distinguish between structural isomers (but not necessarily stereoisomers), including, but not limited to gc/ms (any type, single or tandem) and lc/ms (any type, single or tandem and excluding immunoassays (e.g., ia, eia, elisa, emit, fpia) and enzymatic methods (e.g., alcohol dehydrogenase)), (2) stable isotope or other universally recognized internal standards in all samples (e.g., to control for matrix effects, interferences and variations in signal strength), and (3) method or drug-specific calibration and matrix-matched quality control material (e.g., to control for instrument variations and mass spectral drift); qualitative or quantitative, all sources, includes specimen validity testing, per day; 1-7 drug class(es), including metabolite(s) if performedCarrier judgment—4
G0483Drug test(s), definitive, utilizing (1) drug identification methods able to identify individual drugs and distinguish between structural isomers (but not necessarily stereoisomers), including, but not limited to gc/ms (any type, single or tandem) and lc/ms (any type, single or tandem and excluding immunoassays (e.g., ia, eia, elisa, emit, fpia) and enzymatic methods (e.g., alcohol dehydrogenase)), (2) stable isotope or other universally recognized internal standards in all samples (e.g., to control for matrix effects, interferences and variations in signal strength), and (3) method or drug-specific calibration and matrix-matched quality control material (e.g., to control for instrument variations and mass spectral drift); qualitative or quantitative, all sources, includes specimen validity testing, per day; 22 or more drug class(es), including metabolite(s) if performedCarrier judgment—4
G0482Drug test(s), definitive, utilizing (1) drug identification methods able to identify individual drugs and distinguish between structural isomers (but not necessarily stereoisomers), including, but not limited to gc/ms (any type, single or tandem) and lc/ms (any type, single or tandem and excluding immunoassays (e.g., ia, eia, elisa, emit, fpia) and enzymatic methods (e.g., alcohol dehydrogenase)), (2) stable isotope or other universally recognized internal standards in all samples (e.g., to control for matrix effects, interferences and variations in signal strength), and (3) method or drug-specific calibration and matrix-matched quality control material (e.g., to control for instrument variations and mass spectral drift); qualitative or quantitative, all sources, includes specimen validity testing, per day; 15-21 drug class(es), including metabolite(s) if performedCarrier judgment—4
G0481Drug test(s), definitive, utilizing (1) drug identification methods able to identify individual drugs and distinguish between structural isomers (but not necessarily stereoisomers), including, but not limited to gc/ms (any type, single or tandem) and lc/ms (any type, single or tandem and excluding immunoassays (e.g., ia, eia, elisa, emit, fpia) and enzymatic methods (e.g., alcohol dehydrogenase)), (2) stable isotope or other universally recognized internal standards in all samples (e.g., to control for matrix effects, interferences and variations in signal strength), and (3) method or drug-specific calibration and matrix-matched quality control material (e.g., to control for instrument variations and mass spectral drift); qualitative or quantitative, all sources, includes specimen validity testing, per day; 8-14 drug class(es), including metabolite(s) if performedCarrier judgment—4
G0659Drug test(s), definitive, utilizing drug identification methods able to identify individual drugs and distinguish between structural isomers (but not necessarily stereoisomers), including but not limited to gc/ms (any type, single or tandem) and lc/ms (any type, single or tandem), excluding immunoassays (e.g., ia, eia, elisa, emit, fpia) and enzymatic methods (e.g., alcohol dehydrogenase), performed without method or drug-specific calibration, without matrix-matched quality control material, or without use of stable isotope or other universally recognized internal standard(s) for each drug, drug metabolite or drug class per specimen; qualitative or quantitative, all sources, includes specimen validity testing, per day, any number of drug classesCarrier judgment—4

Medicare policy articles listing Z91.A28

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.

Other Z91 diagnoses (Personal risk factors, not elsewhere classified)

Frequently asked questions

Does Medicare cover Z91.A28 (Caregiver's intentional underdosing of medication regimen…)?

Medicare covers items and services, not diagnoses. 4 Medicare billing and coding articles list Z91.A28 as a covered diagnosis for 5 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 Z91.A28?

The Level II codes from the policies most specific to this diagnosis are G0480 (Drug test(s), definitive, utilizing (1) drug…, 4 articles); G0483 (Drug test(s), definitive, utilizing (1) drug…, 4 articles); G0482 (Drug test(s), definitive, utilizing (1) drug…, 4 articles); G0481 (Drug test(s), definitive, utilizing (1) drug…, 4 articles); G0659 (Drug test(s), definitive, utilizing drug identification…, 4 articles). Code choice depends on the item supplied; check each code's descriptor.

Which Medicare policy articles list Z91.A28?

A55001 (Billing and Coding: Urine Drug Testing); A59416 (Billing and Coding: Urine Drug Testing); A54799 (Billing and Coding: Urine Drug Testing), and 1 more article.

What is ICD-10-CM code Z91.A28?

Z91.A28 is the ICD-10-CM code for Caregiver's intentional underdosing of medication regimen for other reason, in category Z91 (Personal risk factors, not elsewhere classified), chapter 22: Factors influencing health status and contact with health services.

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 22: Factors influencing health status and contact with health services · All diagnoses · HCPCS lookup