We are currently experiencing technical issues. If you are unable to access your results please call 888 GET LABS

Need Help? (888) GET LABS

Thyroxine (T4) Free, Direct Blood Test

* This is not a home test kit. You will need to visit a local lab for testing.

Also Known As

Direct Free T4, Free T4 by Equilibrium Dialysis, Free Thyroxine, FT4 Direct Dialysis

Purpose of the T4 Free Blood Test

A free thyroxine blood test help assesses thyroid health and detects thyroid problems and other related health conditions.

Thyroxine, T4, Free, Direct, Serum (35167)
Thyroxine, T4, Free, Direct, Serum (001974)

What Does the Free T4 Blood Test Measure?

The T4 free blood test measures free thyroxine (T4) in the blood to assess thyroid health. Thyroxine is a hormone produced by the thyroid gland and secreted in the bloodstream.

T4 can be classified into two forms: free thyroxine (FT4) and bound T4. Of the two, FT4 is considered the most accurate in detecting thyroid disease, as it evaluates T4 that enters any tissue that needs it. Whereas, bound T4 is attached to some proteins.

Who Should Take a T4 Free Blood Test?

Take a free T4 blood test as a complementary test for TSH and T3 bloodwork. Additionally, consider the free T4 test, if you have hypothyroidism or hyperthyroidism symptoms, which include the following.

Hypothyroidism Symptoms

  • Dry skin
  • Low libido
  • Brittle nails
  • Constipation
  • Sudden weight gain
  • Extreme tiredness
  • Sensitivity to coldness
  • Anxiety and Depression
  • Muscle pain, cramps, and weakness
  • Tingling sensation in the hands and feet

Hyperthyroidism Symptoms

  • Low libido
  • Weight loss
  • Skin itchiness
  • Extreme fatigue
  • Body weakness
  • Sensitivity to heat
  • Difficulty sleeping
  • Frequent urination
  • Enlarged thyroid (goiter)
  • Anxiety and uneasiness
  • Irregular heartbeat (arrhythmia)

Thyroxine Free Test Preparation

No special preparation is needed prior to blood sample collection.

T4 Free Lab Test Results

The normal range for free T4 is 0.9 to 2.2 nanograms per deciliter (ng/dL).

Test values that go beyond or below the reference interval may suggest thyroid problems. However, the result cannot be conclusive unless other tests are performed, such as the TSH (thyroid-stimulating hormone) blood testT3, total blood testT4 Total blood test, and other thyroid blood tests.

High T4 can be linked to medical conditions like Grave’s disease, thyroiditis (thyroid inflammation), thyroid nodules, and goiter. It can also be attributed to too much intake of thyroid medicine, hormonal changes (especially among women), and liver problems.

On the other hand, low T4 can indicate hypothyroidism, thyroiditis, and malnutrition. Again, these illnesses require additional tests for accurate diagnosis. Simplify the process by taking note of the symptoms you observe.

Where Can I Get a Free Thyroxine Blood Test Done Near Me?

Taking a free thyroxine test can be carried out with these four steps.

Step 1: Go to our website’s thyroid function tests section, and order the thyroxine (T4) free, direct blood test. Then print out the lab test order, which doubles as your doctor’s order for the lab work.

Step 2: Using our lab locator, select a patient partner center where you can have the test done.

Step 3: Proceed to the laboratory you chose during your scheduled blood collection.

Step 4: Wait for the lab test results within 2-10 business days in your Personalabs account.

For an exact turnaround time for results, please contact us at 1-888-438-5227. We will contact the lab of your choice (Quest Diagnostics or LabCorp) as turnaround times vary depending on testing location or lab testing provider.

Additional information


LabCorp, Quest

Arrow icon


Order Your Test

Create an account, choose your tests, checkout securely, generate your lab order



Generate & Print Out Lab Order

Our physician network will approve your order within 2-4hrs.



Visit the Lab

The test price decides which lab you will visit: Quest or Labcorp. Find a location in your area.



Get Your Results

Results can be provided in as little as 24-48 hrs. For more complex tests, please contact us for turn around times.


Save up to
80% on meds!

We now offer pharmacy discounts through our PersonalabsRx platform.

We now offer pharmacy discounts through our PersonalabsRx platform.

Would you like to sign up for PersonalabsRx?