| Watery, no travel, no red flags | No | — | Supportive care only |
| Watery, domestic US travel | No (usually) | — | Treat if septic or immunocompromised |
| Moderate–severe traveler's diarrhea, international | Yes | Azithromycin or fluoroquinolone | Azithromycin preferred for South/SE Asia |
| Bloody + high fever + dysentery | Yes | Azithromycin or fluoroquinolone | Presume Shigella; send stool studies |
| Bloody + low / no fever | No — suspect STEC | — | Antibiotics may cause HUS |
| Bloody + international travel + fever ≥38.5°C or sepsis | Yes | Azithromycin or fluoroquinolone | 3-day course recommended |
| Immunocompromised + severe diarrhea | Yes | Azithromycin or fluoroquinolone | Broader workup warranted |
| Recent antibiotics / hospitalization | Test C. diff first | Vancomycin / fidaxomicin if CDI | Empiric antibiotics worsen CDI |