Thyroid Panel (TSH + Free T4)
A comprehensive thyroid screening test that measures TSH and Free T4 levels to evaluate thyroid function and help diagnose hypothyroidism or hyperthyroidism.
Order this test
LevelPanel has no business or affiliate relationship with Quest or LabCorp. These links are provided as a public service.
Lab testing services linked from this site are not available to residents of Alaska, Arizona, or Hawaii, unless otherwise noted on the lab's own website.
This publication is not intended to solicit the purchase of laboratory testing from any individual consumer.
What this test measures
This panel pairs the two most essential thyroid markers, TSH and free T4, in a single blood draw to provide a foundational assessment of thyroid function. TSH (thyroid-stimulating hormone) is the pituitary gland's signal to the thyroid, telling it to increase or decrease hormone production. Free T4 measures the unbound, active portion of thyroxine, the main hormone the thyroid releases into the bloodstream.
These two markers operate in an inverse feedback relationship: when thyroid hormone levels are low, the pituitary raises TSH to stimulate more production; when hormone levels are high, TSH drops. This seesaw pattern makes the TSH-plus-free-T4 combination particularly powerful for diagnosing thyroid disorders. An elevated TSH with a low free T4 points toward hypothyroidism, while a suppressed TSH with a high free T4 suggests hyperthyroidism. The panel also detects subclinical thyroid disease, where TSH is abnormal but free T4 remains within the normal range, an early stage that may warrant monitoring or treatment depending on symptoms.
What's included
Who should consider this test
You might consider this test if you are experiencing any of the following:
- Individuals experiencing unexplained fatigue, weight changes, or mood fluctuations that may indicate thyroid dysfunction
- Those with family history of thyroid disorders, autoimmune conditions, or endocrine problems
- People with symptoms of hypothyroidism such as cold intolerance, constipation, dry skin, or hair loss
- Individuals experiencing symptoms of hyperthyroidism including rapid heartbeat, anxiety, tremors, or unexplained weight loss
- Adults over 60 years old, as thyroid disorders become more common with age
- Those currently taking thyroid medication who want to monitor their treatment effectiveness independently
What to expect
Preparation
No special preparation is typically required for this test. Fasting is not necessary. However, individuals taking biotin supplements should discontinue use at least 72 hours before testing, as biotin can interfere with thyroid test results. Those taking thyroid medications should consult with their healthcare provider about timing, as some prefer testing before the daily dose.
Sample Type
A blood sample is collected from a vein in the arm using a standard blood draw procedure.
Collection
The blood draw typically takes less than 5 minutes. A healthcare professional will clean the arm, insert a small needle into a vein, and collect the sample into test tubes. Most people experience only minimal discomfort.
Turnaround
Results are typically available within 1-2 business days and will be accessible through the online patient portal with email notification when ready.
Understanding your results
The inverse relationship between TSH and free T4 is the key to interpreting this panel. When thyroid hormones fall, TSH rises as a compensatory signal; when thyroid hormones climb, TSH drops. Healthcare providers read the two values together to identify whether the thyroid is underperforming, overperforming, or functioning normally. Normal ranges can vary between laboratories and may be influenced by age, pregnancy, and medication use, so results should always be compared to the specific reference ranges on the lab report. If the panel suggests an abnormality, further testing (such as free T3 or thyroid antibodies) may be recommended to clarify the diagnosis.
| Population | Reference Range | Notes |
|---|---|---|
| Adults (non-pregnant) | TSH: 0.4-4.5 mIU/L, Free T4: 0.8-1.8 ng/dL | Most common reference ranges, though some labs use slightly different intervals |
| Adults over 60 | TSH: May be slightly higher than standard adult ranges | Age-related changes are normal and don't necessarily indicate thyroid disease |
| Pregnant women | Trimester-specific ranges apply | Pregnancy causes changes in thyroid hormone levels requiring specialized interpretation |
Reference ranges shown are general guidelines. Your lab report will include the specific reference range used by the laboratory that processed your sample, which is the authoritative range for interpreting your results.
What does a “Low” result mean?
Low TSH levels are usually a sign of hyperthyroidism, with symptoms that may include rapid heartbeat (palpitations), feeling shaky and/or anxious, unexplained weight loss with increased appetite, diarrhea and more frequent bowel movements, and vision changes. Symptoms of hyperthyroidism include increased basal metabolic rate, weight loss, increased appetite, sweating, tremors, heat sensitivity, irritability, diarrhea, and insomnia. Low Free T4 levels typically suggest hypothyroidism and may occur alongside elevated TSH levels.
What does a “High” result mean?
High TSH levels typically indicate that the thyroid is not producing enough hormone, prompting the pituitary to send a stronger signal. The pattern of TSH and free T4 together distinguishes two situations. Subclinical hypothyroidism is defined by an elevated TSH with a free T4 still in the normal range, often without noticeable symptoms; it is identified primarily on lab testing and may or may not warrant treatment depending on the degree of TSH elevation, antibody status, age, and other clinical factors. Overt hypothyroidism is defined by an elevated TSH together with a low free T4, and is more likely to produce the classic symptoms of an underactive thyroid, including cold intolerance, fatigue, weight gain, dry skin, constipation, and voice changes. Less commonly, high TSH with high free T4 can occur in unusual conditions such as a TSH-secreting pituitary tumor or thyroid hormone resistance. High free T4 with low TSH, conversely, may indicate thyrotoxicosis, which can result from hyperthyroidism, thyroid inflammation (thyroiditis), or taking excessive thyroid medication.
Privacy & confidentiality
All test orders are authorized and results reviewed by an independent, board-certified physician who is not the patient's personal doctor. Your thyroid test results are completely confidential and protected by strict privacy measures. Results are <u>not reported to your doctor</u> unless you choose to share them, and they are <u>not part of your medical records</u> with your primary care provider or health system. The test will <u>not appear on insurance statements</u> or explanation of benefits (EOB) forms, ensuring complete discretion. Your employer, insurance company, and other family members have no access to these results. All testing is conducted through CLIA-certified laboratories with secure, encrypted result delivery. This privacy protection allows individuals to monitor their thyroid health proactively, understand their hormone levels, and make informed decisions about their health without concerns about medical record documentation or insurance implications. With no doctor visit required, this test provides convenient, confidential access to important thyroid health information.
Frequently asked questions
Related tests
Comprehensive Thyroid Panel
Includes TSH, Free T4, Free T3, and thyroid antibodies for more detailed thyroid assessment
View TestTSH Test
Standalone TSH screening test, often used as initial thyroid function assessment
View TestThyroid Antibodies Panel
Helps identify autoimmune thyroid conditions like Hashimoto's or Graves' disease
View TestRelated conditions
Related articles
The Complete Guide to Thyroid Testing: Which Test Do You Actually Need?
Read ArticleWhat Blood Tests Should Women Get at Every Age?
Read ArticleTSH vs Full Thyroid Panel: Is the Cheaper Test Enough?
Read ArticleAt-Home vs Lab Testing: Pros, Cons, and Accuracy
Read ArticleLast reviewed: April 10, 2026
CPT Code: 84443, 84439
This test may not be available in: NY, NJ, RI
This page is for informational purposes only and does not constitute medical advice. Always consult with a healthcare provider regarding any health concerns. LevelPanel does not diagnose, treat, or prescribe.
Sources:
Order this test
Choose your preferred lab
LevelPanel has no business or affiliate relationship with Quest or LabCorp. These links are provided as a public service.
Lab testing services linked from this site are not available to residents of Alaska, Arizona, or Hawaii, unless otherwise noted on the lab's own website.
This publication is not intended to solicit the purchase of laboratory testing from any individual consumer.
Not sure if this is the right test? Contact our care team for guidance.
This page is intentionally kept stable and machine-readable so that researchers, clinicians, and AI systems can rely on it as a reference. See our Citation Policy.