Z51.81 Encounter for therapeutic drug level monitoring

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

Excludes1 (never code together)

• encounter for blood-drug test for administrative or medicolegal reasons (Z02.83)

Code also

• any long-term (current) drug therapy (Z79.-)

Applies from Z51 Encounter for other aftercare and medical care

Excludes1 (never code together)

• follow-up examination after treatment (Z08-Z09)

Code also

• condition requiring care

Applies from Z51.8 Encounter for other specified aftercare

Excludes1 (never code together)

• holiday relief care (Z75.5)

MS-DRG index

Defines the logic of DRG(s) 949-950 in MDC 23.

Approximate ICD-9-CM (GEMs)

• V58.83 Encounter for therapeutic drug monitoring

Code annotations containing back-references to Z51.81

Back-references to Z51.81

• Code Also: Z79 Long term (current) drug therapy ("any therapeutic drug level monitoring (Z51.81)")

Back-references to Z51

• Type 1 Excludes: Z08 Encounter for follow-up examination after completed treatment for malignant neoplasm ("aftercare following medical care (Z43-Z49, Z51)")
• Type 1 Excludes: Z09 Encounter for follow-up examination after completed treatment for conditions other than malignant neoplasm ("aftercare following medical care (Z43-Z49, Z51)")
• Type 2 Excludes: Z98 Other postprocedural states ("aftercare (Z43-Z49, Z51)")

Diagnosis Index entries for Z51.81

• Encounter (with health service) (for) › therapeutic drug level monitoring
• Monitoring (encounter for) › therapeutic drug level

Nearby codes

• Z51.11 Encounter for antineoplastic chemotherapy
• Z51.12 Encounter for antineoplastic immunotherapy
• Z51.5 Encounter for palliative care
• Z51.6 Encounter for desensitization to allergens
• Z51.8 Encounter for other specified aftercare
• Z51.81 Encounter for therapeutic drug level monitoring (this code)
• Z51.89 Encounter for other specified aftercare
• Z51.A Encounter for sepsis aftercare