The Free Thyroxine (T4) test is a blood test that measures the level of unbound or “free” thyroxine in the bloodstream. T4 is one of the two main hormones produced by the thyroid gland, the other being triiodothyronine (T3). These thyroid hormones play a crucial role in regulating the body’s metabolism, energy production, and overall growth and development.

Sample type:  Blood
Preparation:  For accurate Free T4 blood test results, overnight fasting is generally not required, but adherence to specific medication instructions and morning sample collection is recommended.

Price: $37


T4 Free test are usually reported in picograms per milliliter (pg/mL) or other similar units. It’s important to note that reference ranges may vary between laboratories, and interpretation should be done in consultation with a healthcare provider.

The T4 Free test provides valuable information about thyroid function and aids in the diagnosis and management of thyroid disorders.

Free Thyroxine (T4): T4 is produced by the thyroid gland and is released into the bloodstream. Most of the T4 in the blood is bound to proteins, but a small fraction circulates freely and is biologically active. This free T4 is the form of the hormone that can enter cells and exert its metabolic effects.

Thyroid Function: The T4 Free test is used to evaluate thyroid function and helps diagnose conditions such as hyperthyroidism (elevated thyroid function) or hypothyroidism (reduced thyroid function). In hyperthyroidism, free T4 levels are often elevated, while in hypothyroidism, they may be lower than normal.

Monitoring Thyroid Treatment: For individuals with thyroid disorders who are undergoing treatment, the T4 Free test is frequently used to monitor the effectiveness of medication dosage. Adjustments to thyroid medications may be made based on the results to ensure that thyroid hormone levels are within the target range.

Pituitary Gland Regulation: The T4 Free test is often interpreted in conjunction with TSH levels. TSH, produced by the pituitary gland, stimulates the thyroid to produce and release T4. Abnormalities in T4 levels, along with TSH, can help identify whether the thyroid dysfunction is primary (related to the thyroid gland) or secondary (related to the pituitary gland).