Z51.81 — Encounter for therapeutic drug level monitoring
Is Z51.81 billable?
Yes — Z51.81 is billable for FY2027. Z51.81 is a valid, billable ICD-10-CM code at the highest level of specificity in its branch. Z51.81 may be submitted for encounters from October 1, 2026 through September 30, 2027.
Z51.81 at a glance
| Code | Z51.81 |
|---|---|
| Description | Encounter for therapeutic drug level monitoring |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
Which MS-DRGs does Z51.81 group to?
Z51.81 sits in MDC 23 and helps define the logic of 2 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 949Aftercare with CC/MCCmedical
- 950Aftercare without CC/MCCmedical
How is Z51.81 listed in the Alphabetic Index?
These are the routes through the Alphabetic Index that lead to Z51.81. They show the wording a clinician may have documented, which often differs from the Tabular description.
- Encounter › therapeutic drug level monitoring (with health service) (for)
- Monitoring › therapeutic drug level (encounter for)
Excludes1 — never code together
The conditions below can never be reported together with Z51.81 on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
- encounter for blood-drug test for administrative or medicolegal reasons (Z02.83)
Code also
Two codes may be needed to describe the condition fully. Whether Z51.81 is sequenced first depends on the reason for the encounter.
- any long-term (current) drug therapy (Z79.-)
Excludes1 — never code together — inherited from Z51
The conditions below can never be reported together with Z51.81 on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
- follow-up examination after treatment (Z08-Z09)
Excludes1 — never code together — inherited from Z51.8
The conditions below can never be reported together with Z51.81 on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
- holiday relief care (Z75.5)
Excludes2 — not included here — inherited from Z40-Z53
The conditions below are not part of Z51.81, but a patient may have both at the same time. When documentation supports it, Z51.81 and the excluded code may both be reported.
- follow-up examination for medical surveillance after treatment (Z08-Z09)
Code also — inherited from Z51
Two codes may be needed to describe the condition fully. Whether Z51.81 is sequenced first depends on the reason for the encounter.
- condition requiring care
How long has Z51.81 existed?
Z51.81 has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.