# Complement C4a

> This test measures Complement C4a, a protein released when your immune system is activated. It helps show whether your body is reacting with inflammation to a trigger, such as an infection or an autoimmune issue.

- Labcorp code: 004330
- Category: [Immune Regulation](https://picardo.health/labs/tests/immune-regulation.md)
- Sample: blood
- Labcorp turnaround: 4–7 days
- Collection: free at a Labcorp location, or $75.00 at home.
- Without a doctor: yes. People order it themselves, with no doctor's visit or referral.
- Price: shown on the review page its order link opens. Opening it orders nothing.
- Order link: https://app.picardo.health/labs/order?tests=004330&ref=assistant

## About ordering

People order for themselves, with no doctor's visit or referral, and results arrive in their Picardo account. Ordering is open to adults 18 and over in the US, except New York, New Jersey, Rhode Island, Pennsylvania, Maryland, Massachusetts, Hawaii and Maine. General health information, not medical advice.