Z51.81 – Encounter for therapeutic drug level monitoring

ICD-10-CM 2027 diagnosis code · Encounters for other specific health care

Billable code

ICD-10-CM code Z51.81

Code: Z51.81 (claims format: Z5181)
Description: Encounter for therapeutic drug level monitoring
Billable: Yes – valid for HIPAA-covered transactions
Valid for: Dates of service October 1, 2026 – September 30, 2027 (FY2027)
Chapter: 21. Factors influencing health status and contact with health services (Z00-Z99)
Block: Z40-Z53 Encounters for other specific health care
Parent codes: Z51 › Z51.8

Notes for Z51.81

Excludes1 (not coded here):

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

Code also:

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

Notes inherited from parent codes

Instructional notes at a category or block level apply to every code below it.

Z51 – Encounter for other aftercare and medical care

Excludes1 (not coded here):

follow-up examination after treatment (Z08-Z09)

Code also:

condition requiring care

Z51.8 – Encounter for other specified aftercare

Excludes1 (not coded here):

holiday relief care (Z75.5)

Block Z40-Z53

Applicable to:

Categories Z40-Z53 are intended for use to indicate a reason for care. They may be used for patients who have already been treated for a disease or injury, but who are receiving aftercare or prophylactic care, or care to consolidate the treatment, or to deal with a residual state

Excludes2 (not included here):

follow-up examination for medical surveillance after treatment (Z08-Z09)

Index terms for Z51.81

Entries in the ICD-10-CM alphabetic index that lead to this code:

Related codes in Z51.8

Z51.89 – Encounter for other specified aftercareBillable

Frequently asked questions

What is ICD-10 code Z51.81?

Z51.81 is the ICD-10-CM code for encounter for therapeutic drug level monitoring, in the block Z40-Z53 (Encounters for other specific health care).

Is Z51.81 a billable code?

Yes. Z51.81 is a billable/specific code that can be used to indicate a diagnosis for reimbursement purposes.

What category does Z51.81 belong to?

It belongs to category Z51 – Encounter for other aftercare and medical care.

Source: CDC/NCHS ICD-10-CM FY2027 code files, tabular list and index. Reference only – code assignment must follow the official ICD-10-CM guidelines and documentation in the medical record.