Z91.A3 Caregiver's unintentional underdosing of patient's medication regimen

Billable ICD-10-CM code, FY2026. Exempt from present-on-admission (POA) reporting.

Code first

• underdosing of medication (T36-T50) with fifth or sixth character 6

Applies from Z91 Personal risk factors, not elsewhere classified

Excludes2 (not included here)

• contact with and (suspected) exposures hazardous to health (Z77.-)
• exposure to pollution and other problems related to physical environment (Z77.1-)
• female genital mutilation status (N90.81-)
• occupational exposure to risk factors (Z57.-)
• personal history of physical injury and trauma (Z87.81, Z87.82-)

MS-DRG index

Defines the logic of DRG(s) 951 in MDC 23.

Medicare Code Edits (MCE v43.1 (April 2026))

• Unacceptable principal diagnosis: These codes describe a circumstance which influences care but is not a current illness or injury, or capture only an underlying condition, and are unacceptable as principal diagnosis.

Code annotations containing back-references to Z91.A3

Back-references to Z91.A

• Type 2 Excludes: Z91.1 Patient's noncompliance with medical treatment and regimen ("caregiver noncompliance with patient's medical treatment and regimen (Z91.A-)")

Diagnosis Index entries for Z91.A3

• Noncompliance › with › medication regimen NEC › underdosing › unintentional NEC › by caregiver

Nearby codes

• Z91.A10 Caregiver's noncompliance with patient's dietary regimen due to financial hardship
• Z91.A18 Caregiver's noncompliance with patient's dietary regimen for other reason
• Z91.A2 Caregiver's intentional underdosing of patient's medication regimen
• Z91.A20 Caregiver's intentional underdosing of patient's medication regimen due to financial hardship
• Z91.A28 Caregiver's intentional underdosing of medication regimen for other reason
• Z91.A3 Caregiver's unintentional underdosing of patient's medication regimen (this code)
• Z91.A4 Caregiver's other noncompliance with patient's medication regimen
• Z91.A41 Caregiver's other noncompliance with patient's medication regimen due to financial hardship
• Z91.A48 Caregiver's other noncompliance with patient's medication regimen for other reason
• Z91.A5 Caregiver's noncompliance with patient's renal dialysis
• Z91.A51 Caregiver's noncompliance with patient's renal dialysis due to financial hardship