# 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. Doctors use this result to evaluate immune system activity and monitor inflammatory conditions. However, because C4a levels rise in many different situations, this test cannot diagnose a specific disease or pinpoint the exact cause of the inflammation on its own.

- Labcorp code: 004330
- Category: [Immune Regulation](https://app.picardo.health/labs/tests/immune-regulation.md)
- Price: shown at checkout, before payment.
- Blood draw: free at a Labcorp location, or $75.00 at home.
- Order link: https://app.picardo.health/labs/order?tests=004330&ref=assistant

## About ordering

A licensed physician reviews every order before any test is run, and results arrive in the person's 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.