Z91.138 Patient's unintentional underdosing of medication regimen for other reason

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

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-)

Applies from Z91.1 Patient's noncompliance with medical treatment and regimen

Excludes2 (not included here)

• caregiver noncompliance with patient's medical treatment and regimen (Z91.A-)

Code also

• , if applicable, to identify underdosing of specific drug (T36-T50 with final character 6)

Applies from Z91.13 Patient's unintentional underdosing of medication regimen

Code first

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

MS-DRG index

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

Approximate ICD-9-CM (GEMs)

• V15.81 Personal history of noncompliance with medical treatment, presenting hazards to health (approximate)

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.

Diagnosis Index entries for Z91.138

• Noncompliance › with › medication regimen NEC › underdosing › unintentional NEC
• Underdosing › unintentional NEC

Nearby codes

• Z91.12 Patient's intentional underdosing of medication regimen
• Z91.120 Patient's intentional underdosing of medication regimen due to financial hardship
• Z91.128 Patient's intentional underdosing of medication regimen for other reason
• Z91.13 Patient's unintentional underdosing of medication regimen
• Z91.130 Patient's unintentional underdosing of medication regimen due to age-related debility
• Z91.138 Patient's unintentional underdosing of medication regimen for other reason (this code)
• Z91.14 Patient's other noncompliance with medication regimen
• Z91.141 Patient's other noncompliance with medication regimen due to financial hardship
• Z91.148 Patient's other noncompliance with medication regimen for other reason
• Z91.15 Patient's noncompliance with renal dialysis
• Z91.151 Patient's noncompliance with renal dialysis due to financial hardship