Reference Guide
Vibrant America
Free T3

Free T3

Vibrant America
Free T3
Vibrant America
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About the Test

*This is a single-marker test measuring free triiodothyronine (fT3). It can be ordered as part of a custom panel.

Ordering the Free T3 with Vibrant America

A free T3 test measures Free Triiodothyronine (T3) level in the blood.

T3 levels are regulated by the feedback system that the body uses to maintain stable amounts of thyroid hormones in the blood. Most of the hormone produced by the thyroid is T4. This hormone is relatively inactive but is converted into the much more active T3 in the liver and other tissues.

T3 and T4 are two hormones that work together to regulate the body’s metabolism. These hormones play an essential role in controlling

the body’s weight, body temperature, muscle strength, and nervous system.

The T3 hormone is present in the blood in two forms:

Bound T3: which attaches to protein.

Free T3: which does not attach to anything (i.e., its free).

Both may be used to check T3 levels.

Since most T3 is bound to protein, the total T3 can be affected by protein levels in the body. Free T3 is not affected by protein levels.

Why is Free T3 Tested?

  • To help evaluate thyroid gland function.
  • To diagnose thyroid disease.
  • To monitor the effectiveness of treatment of a thyroid disorder.
  • T3 tests are frequently ordered together with T4 and TSH tests to have a complete picture of the thyroid function.

Which Patients is the Free T3 with Vibrant America Test Best Used For?

A T3 test is frequently requested to diagnose hyperthyroidism, a condition in which the body produces too much thyroid hormone.

Hyperthyroidism symptoms include:

  • Anxiety
  • High Metabolism
  • Tremors in the hands
  • Low tolerance for heat
  • Increased heart rate
  • Bulging of the eyes
  • Trouble sleeping
  • Fatigue

About the Test

This is a single-marker test measuring free T3. It is used to evaluate thyroid function.

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Lab Test Information
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Lab Company
Vibrant America
Sample Type
Shipping Time
3 - 5 days
Turnaround Time
14 days
Test Preparation Starts
Up to 1 day before collection
Number of Collection Days
1 day
Methods Used For Processing
Lab Certifications
CLIA Certified
CAP Accredited
ISO 15189
COLA Accredited
Order, track, and receive results from 30+ labs in one place.