ICD-10 Code A07.3 – Isosporiasis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A07.3 – Isosporiasis
What it is
A07.3 identifies isosporiasis, an intestinal infection caused by the parasite Cystoisospora belli. Use this code when documentation states the diagnosis or a confirmed infection with this organism.
Clinical signs
Clinical features often include watery diarrhea, abdominal cramping, and weight loss. In immunocompromised patients, infection may be prolonged or severe; if details are unclear, refer to documentation.
When to use this code
Use A07.3 when the provider documents isosporiasis, Cystoisospora infection, or confirmed intestinal infection due to this parasite. It may also apply when the record shows parasite identification with compatible gastrointestinal illness. If the chart only says “diarrhea,” do not assume this code.
Do not use for
Do not use this code for unspecified infectious diarrhea, other protozoal intestinal diseases, or noninfectious gastrointestinal symptoms. Check documentation if the organism is not named.
Coding tip
Assign A07.3 only when the parasite or isosporiasis is clearly documented; otherwise, code the symptom or unspecified diagnosis.