> ## Documentation Index
> Fetch the complete documentation index at: https://glossary.micahealth.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Phase

The stage of testing for a drug or biological product, defined by the FDA into five categories: Early Phase 1, Phase 1, Phase 2, Phase 3, and Phase 4. Each phase has different objectives and participant numbers. Non-drug studies (like device or behavioral studies) are marked as "Not Applicable.”

## Related terms

<CardGroup cols={3}>
  <Card title="Protocol" href="protocol" />

  <Card title="Study registry" href="study_registry" />
</CardGroup>

[*Source*](https://clinicaltrials.gov/study-basics/glossary)