# Thyroxine (T4), Thyroxine-binding Globulin (TBG), and T4−TBG Index

> This test measures the total amount of thyroxine (T4) in your blood and the protein that carries it, called thyroxine-binding globulin (TBG). By comparing these levels, the test calculates an index that estimates how much thyroid hormone is actually available for your body to use.

- Labcorp code: 004457
- Category: [Thyroid](https://picardo.health/labs/tests/thyroid.md)
- Sample: blood
- Labcorp turnaround: 2–3 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=004457&ref=assistant

## Results reported (3)

- Thyroxine (T4)
- Thyroxine Binding Globulin
- T4-TBG Index

## 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.