# Thyroxine (T4), Free, Dialysis/Mass Spectrometry (Endocrine Sciences)

> This test measures the precise amount of free T4, a thyroid hormone available for your body to use, using a specialized technique that filters out interfering proteins. It helps show whether your thyroid is functioning properly, particularly in complex cases where standard tests might be inaccurate due to pregnancy, severe illness, or medications. These results help doctors determine if an overactive or underactive thyroid is responsible for symptoms affecting your metabolism. However, this test only reports hormone levels and does not identify the specific disease or underlying cause of the thyroid dysfunction.

- Labcorp code: 501902
- Category: [Thyroid](https://app.picardo.health/labs/tests/thyroid.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=501902&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.