T4, Free Blood Test

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Feature	Labcorp	Quest Diagnostics
Price	$13.49	$7.49
Results in	~2 business days	~5 business days
Sample type	Blood Serum	Blood Serum
Require fasting	No	No

About the test

T4, Free measures the unbound, biologically active form of thyroxine in the blood. It is a key indicator of thyroid function and is commonly used to evaluate thyroid disorders, especially when TSH levels are abnormal.

Included biomarkers & Reference ranges

Biomarker	Reference range
T4, Free (fT4) The unbound, biologically active portion of thyroxine (T4), your main thyroid hormone. A core marker for evaluating thyroid function.	0.8–1.8 ng/dL

Reference ranges vary by lab, age, and sex (M/F). Your report shows your exact range. Click any biomarker to see its optimal range and what your results mean.

Preparation

If you are taking or have recently taken heparin, please consult your healthcare provider before collecting your sample. This medication may affect your results.

Quest Diagnostics lists no special preparation for this test.

How it works

1. Order online No referral or insurance
2. Get a requisition By email in 24–72 hours
3. Visit a draw center Bring a matching photo ID
4. Get results Securely by email

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

Consultations

Not sure how to read your results? We can help.

Schedule a consultation with a Hormunity specialist. We’ll walk through every marker, interpret what it means for you, and map out the next steps for your care.

Book a specialist