Quick Facts
- Sample: Blood serum or plasma
- Fasting: No fasting required
- Turn-around: 1-2 business days. May take longer based on weather, holiday, or lab delays.
Benefits
- Quick thyroid health assessment - Get comprehensive results within 1-2 business days
- No doctor referral needed - Order directly and conveniently online
- Early detection advantage - Catch thyroid disorders before symptoms worsen
- Monitor therapy effectiveness - Track hormone replacement treatment progress
- Confidential results - Secure delivered to online portal
- Accurate dual-hormone testing - Measures both active T4 and regulatory TSH
Who Is This Test For?
- Individuals experiencing unexplained fatigue, weight changes, or mood swings
- People with family history of thyroid disorders or autoimmune conditions
- Those monitoring existing thyroid treatment or hormone replacement therapy
- Health-conscious individuals seeking preventive thyroid screening
- Women experiencing fertility issues or irregular menstrual periods
- Anyone with symptoms like hair loss, irregular heartbeat, or temperature sensitivity
How It Works – Just 3 Steps
- Order online - No appointment needed, choose your convenient lab location
- Visit lab for blood draw - Quick venipuncture, takes just a few minutes
- Receive secure results - Get results within 1-2 business days
FAQ
What does this test measure? This panel measures free T4 (active thyroid hormone) and TSH (thyroid-stimulating hormone) to evaluate thyroid function.
Do I need to fast before this test? No fasting is required, but avoid biotin supplements for 72 hours before testing to prevent interference.
How accurate is this test? The combination of free T4 and TSH provides high diagnostic accuracy using quantitative electrochemiluminescent immunoassay methods.
Can medications affect my results? Yes, thyroid medications and high-dose biotin can interfere. Inform your lab about all medications and supplements.
What if my results are abnormal? Abnormal results require clinical correlation. We recommend consulting with a healthcare provider for proper interpretation and next steps.
How often should I get tested? Testing frequency depends on your health status - typically every 6-12 months for stable patients, more frequently during treatment adjustments.
More Details
What is the purpose of this test?
This panel evaluates thyroid gland function by measuring free thyroxine (T4) and thyroid-stimulating hormone (TSH) levels in your blood. Free T4 is the active thyroid hormone available to body tissues, while TSH is a pituitary hormone that regulates thyroid hormone production (American Thyroid Association 2023). The test helps diagnose thyroid disorders such as hypothyroidism and hyperthyroidism by assessing hormone balance and feedback mechanisms critical to metabolism and overall health.
Who would benefit from this test?
This test is essential for health-conscious individuals who want direct access to thyroid health information without initial physician referral (MedlinePlus 2024). It provides timely insight into thyroid function, enabling early detection of thyroid imbalances that affect energy, weight, mood, and cardiovascular health. The panel is particularly valuable for individuals with symptoms of thyroid dysfunction, those monitoring thyroid therapy, or anyone seeking preventive thyroid health screening.
When should I order this test?
Order this test when experiencing symptoms like fatigue, weight changes, mood shifts, irregular heartbeat, or temperature sensitivity. It's also recommended for monitoring known thyroid conditions, evaluating treatment effectiveness, or as part of preventive health screening (Cleveland Clinic 2025). Women with fertility issues or irregular menstrual periods should also consider this test, as thyroid disorders can significantly impact reproductive health.
How do I interpret the results?
High TSH (>4.0 mIU/L) & Low Free T4 (<0.6 ng/dL)
- What it means: Hypothyroidism
- Typical action: Hormone replacement therapy
Low TSH (<0.4 mIU/L) & High Free T4 (>1.1 ng/dL)
- What it means: Hyperthyroidism
- Typical action: Antithyroid medication
Normal TSH (0.4-4.0 mIU/L) & Normal Free T4 (0.6-1.1 ng/dL)
- What it means: Healthy thyroid function
- Typical action: No treatment needed
High TSH & Normal Free T4
- What it means: Subclinical hypothyroidism
- Typical action: Monitor or mild treatment
Low TSH & Normal Free T4
- What it means: Subclinical hyperthyroidism
- Typical action: Monitor or mild treatment
Approximately 4.6% of the U.S. population has hypothyroidism, with many cases undiagnosed, highlighting the importance of screening.
Disclaimer: Reference ranges may vary by laboratory. Listed ranges are general guidelines and may differ from those used by the performing lab. Always consult your healthcare provider for interpretation.
Pre-test preparation
Generally no fasting is required for this test. However, avoid biotin supplements for at least 72 hours before testing to prevent assay interference (LabCorp). Inform the lab of any thyroid medications or supplements you're taking, as these may affect results. The blood draw is performed via venipuncture into serum or plasma separator tubes, with specimens processed promptly for accurate results.
How often should I get tested?
- Healthy adults (preventive screening): Every 2–3 years after age 35
- Stable thyroid condition: Every 6–12 months
- New thyroid diagnosis: Every 6–8 weeks initially
- Medication adjustment: Every 6–8 weeks
- High-risk individuals: Annually
- Pregnancy planning/monitoring: As recommended by physician
Why early detection matters
Early detection and treatment of thyroid disorders reduce risks of cardiovascular disease, infertility, and metabolic complications, improving quality of life and reducing healthcare costs. Thyroid dysfunction affects metabolism, energy levels, heart rate, weight control, and mood regulation. The diagnostic accuracy of free T4 combined with TSH testing improves sensitivity and specificity for thyroid dysfunction compared to T4 testing alone, enabling prompt clinical intervention and better patient outcomes.
Related tests you may consider
Thyroid Antibodies Panel - Assesses autoimmune thyroid diseases like Hashimoto's or Graves' disease
Tri-iodothyronine (T3) Free Serum Test - Provides additional insight into thyroid hormone activity, especially in hyperthyroidism evaluation
Thyroglobulin Panel Blood Test - Useful in monitoring thyroid cancer patients or evaluating thyroid tissue status post-treatment
