Z51.81 — Encounter for therapeutic drug level monitoring

Z51.81

ICD-10 Chapter 21: Factors Influencing Health Status — illustrative image — Chapter 21: Factors influencing health status and contact with health services (Z00–Z99) — illustrative image

What this code means

An encounter for therapeutic drug level monitoring: blood tests to check a medicine's level, such as for transplant or seizure medicines.

Also called: drug level monitoring, therapeutic drug monitoring.

When this code is used

Used for encounter for therapeutic drug level monitoring.

Where it sits in ICD-10-CM

Code Z51.81 belongs to Chapter 21: Factors influencing health status and contact with health services, which covers codes Z00–Z99 in the FY2027 ICD-10-CM tabular list. The official description above is copied verbatim from the CDC/NCHS FY2027 code file.

Learn more about this condition

Condition guide: Transplantation

Frequently asked questions

What is ICD-10-CM code Z51.81?

Z51.81 is the ICD-10-CM diagnosis code for “Encounter for therapeutic drug level monitoring”. An encounter for therapeutic drug level monitoring: blood tests to check a medicine's level, such as for transplant or seizure medicines.

When is code Z51.81 used?

Used for encounter for therapeutic drug level monitoring. It belongs to Chapter 21 of ICD-10-CM (Factors influencing health status and contact with health services).

This guide explains ICD-10-CM codes in plain language for patients, students and other readers. It is educational information only — not coding, billing or medical advice. The code recorded for any real encounter is assigned from the full clinical documentation by the treating team and qualified coders, and only they can decide which code fits a specific case.