Z77.121 — Contact with and (suspected) exposure to harmful algae and algae toxins
Is Z77.121 billable?
Yes — Z77.121 is billable for FY2027. Z77.121 is a valid, billable ICD-10-CM code at the highest level of specificity in its branch. Z77.121 may be submitted for encounters from October 1, 2026 through September 30, 2027.
Z77.121 at a glance
| Code | Z77.121 |
|---|---|
| Description | Contact with and (suspected) exposure to harmful algae and algae toxins |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
What Medicare edits apply to Z77.121?
The Medicare Code Editor screens inpatient claims before they are grouped. These edits name Z77.121 directly.
CMS will reject this code as the principal diagnosis on an inpatient claim. It describes something other than the condition chiefly responsible for the admission.
Which MS-DRGs does Z77.121 group to?
Z77.121 sits in MDC 23 and helps define the logic of 1 MS-DRG (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 951Other Factors Influencing Health Statusmedical
How is Z77.121 listed in the Alphabetic Index?
These are the routes through the Alphabetic Index that lead to Z77.121. They show the wording a clinician may have documented, which often differs from the Tabular description.
- Contact › algae and algae toxins (with)
- Contact › algae bloom (with)
- Contact › blue-green algae bloom (with)
- Contact › brown tide (with)
- Contact › cyanobacteria bloom (with)
- Contact › pfiesteria piscicida (with)
- Contact › red tide (with)
- Exposure › algae and algae toxins (to)
- Exposure › algae bloom (to)
- Exposure › blue-green algae bloom (to)
- Exposure › brown tide (to)
- Exposure › cyanobacteria bloom (to)
Inclusion terms
Alternative wording in documentation that is classified to Z77.121.
- Contact with and (suspected) exposure to (harmful) algae bloom NOS
- Contact with and (suspected) exposure to blue-green algae bloom
- Contact with and (suspected) exposure to brown tide
- Contact with and (suspected) exposure to cyanobacteria bloom
- Contact with and (suspected) exposure to Florida red tide
- Contact with and (suspected) exposure to pfiesteria piscicida
- Contact with and (suspected) exposure to red tide
Excludes2 — not included here — inherited from Z77
The conditions below are not part of Z77.121, but a patient may have both at the same time. When documentation supports it, Z77.121 and the excluded code may both be reported.
- contact with and (suspected) exposure to communicable diseases (Z20.-)
- exposure to (parental) (environmental) tobacco smoke in the perinatal period (P96.81)
- newborn affected by noxious substances transmitted via placenta or breast milk (P04.-)
- occupational exposure to risk factors (Z57.-)
- retained foreign body (Z18.-)
- retained foreign body fully removed (Z87.821)
- toxic effects of substances chiefly nonmedicinal as to source (T51-T65)
Code also — inherited from Z77-Z99
Two codes may be needed to describe the condition fully. Whether Z77.121 is sequenced first depends on the reason for the encounter.
- any follow-up examination (Z08-Z09)
How long has Z77.121 existed?
Z77.121 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.