About the Test
Purpose of the test
The thyroid panel is used to see how well the thyroid gland is functioning. This gland is responsible for producing hormones important for many bodily processes. Abnormal thyroid function, such as underactive thyroid (hypothyroidism) or overactive thyroid (hyperthyroidism), can lead to many symptoms. By measuring levels of thyroid hormones in the blood, the panel can help diagnose thyroid disorders and disrupted thyroid function.
A thyroid panel can also be used to monitor the treatment of hyperthyroidism and assess those receiving levothyroxine therapy, which replaces or supplements thyroid hormones reduced or absent due to hypothyroidism, thyroid cancer, thyroid nodules, and goiters.
What does the test measure?
The thyroid panel uses one blood sample to test for multiple elements related to thyroid function. Specifically, it measures the amounts of thyroid hormones and thyroid-stimulating hormones in the body.
Three hormones are part of a standard thyroid panel:
When should I get this test?
Consider getting a thyroid panel if you feel symptoms of hyperthyroidism or hypothyroidism. The tricky thing is the symptoms are varied and can be easily overlooked.
Common signs of an overactive thyroid:
- Nervousness, anxiety, and irritability
- Mood swings
- Difficulty sleeping
- Tiredness
- Heat sensitivity
- Diarrhea
- Frequent urination
- Persistent thirst
- Itchiness
- Loss of interest in sex
Symptoms of an underactive thyroid include:
- Tiredness
- Sensitivity to cold
- Weight gain
- Constipation
- Depression
- Slow movements and thoughts
- Muscle aches and weakness
- Muscle cramps
Another reason to get a thyroid test is if you are currently undergoing thyroid treatment and your doctor wants to determine whether it is effective or if your thyroid feels enlarged.
Finding a Thyroid Test
How can I get a thyroid test?
A thyroid panel requires a blood sample. Laboratory testing involves using a needle to remove a small amount of blood from a vein in your arm. The procedure can happen in the doctor’s office, hospital, or a lab testing site.
In most cases, a thyroid panel is ordered by a doctor. Sometimes the thyroid panel analysis is automatically done by the lab on the original blood sample if an initial evaluation finds abnormal levels of thyroid-stimulating hormone.
You can also order a thyroid test online and receive a kit in the mail with the supplies you need to collect your sample and send it back to the lab for analysis. For example, this Thyroid Stimulating Hormone, Blood Spot measures TSH using a blood spot card.
Another option is to get a test online without a doctor’s order and visit the participating lab to provide a sample. If you choose to test at home or order your panel online, follow up with your doctor to discuss the results and next steps.
Can I take the test at home?
At-home thyroid test kits are commercially available without a prescription and measure the same hormones as the traditional thyroid panel. For at-home testing, you prick your finger to get the necessary blood sample. Often, the sample is applied to a blood spot card. That sample is then mailed to a laboratory that conducts the thyroid panel and makes the results available to you directly, often through a secure online portal.
If you are looking for at-home thyroid testing or want to order a panel online and go to a lab without a doctor’s order, there are several options.
While at-home testing can measure thyroid levels, it is generally not a substitute for a test ordered by your doctor. If an at-home test detects abnormal thyroid levels, your doctor will likely recommend a new blood sample and thyroid panel to confirm the results. At-home tests for thyroid labs may not be as accurate as tests done in a laboratory.
How much does the test cost?
The cost of a thyroid panel depends on your insurance coverage and where the test is performed. If ordered by a doctor, insurance normally covers a thyroid panel except for any patient cost-sharing, such as copays or deductibles. Check with your health plan and health care provider for specific cost details.
Your insurance may cover thyroid panel testing in a doctor’s office, hospital or lab, but you will be responsible for all associate copays or deductible expenses.
Taking a Thyroid Test
The thyroid panel test is performed on a blood sample. If a doctor performs the test, the blood sample comes from drawing blood from a vein with a needle. And if the test is being performed at home, the kit typically contains a lancet, which pricks the finger to draw blood that you place on a card to send back to the lab.
Before the test
No special preparation is required for the blood draw. But to ensure the accuracy of the thyroid panel analysis, tell your doctor about any prescription or over-the-counter medications you are taking.
If you take thyroid hormone as treatment for thyroid disease, your blood sample should be drawn before you take your daily dose. Also, tell your doctor if you are feeling sick before the test. The blood draw is usually postponed if you are ill or hospitalized because some illnesses can affect test results.
During the test
A medical professional in a doctor’s office or lab will take a blood sample for the thyroid panel by inserting a needle into a vein in your arm. They may use a tourniquet on your upper arm, and the puncture site will be disinfected before the blood is drawn.
You may experience a brief sting from the needle, but the pain is normally minimal and short-lived. The blood draw itself typically lasts less than a minute.
For at-home testing, you collect the blood sample after pricking one of your fingertips and applying the blood to the supplied card. A home test kit includes instructions on properly preparing this blood sample for the lab. Be sure to read all instructions carefully before collecting a sample.
After the test
Once the blood draw is complete, a bandage or cotton swab will be used to prevent bleeding. It is likely you will need to keep this in place for an hour or more. You can return to normal activities, including driving, once the test is over, and may be advised to avoid strenuous activity with your arm for a few hours after the test. If you notice any persistent pain, bleeding, or signs of infection, contact your doctor.
There are usually no limitations on activity after the test for fingerstick tests used in home testing kits.
Thyroid Test Results
Receiving test results
For laboratory and in-home test kits, results are usually available within a few business days after the sample is received. Some at-home test kits say to allow for one to two business weeks for results.
If your doctor ordered the test, you may have a follow-up appointment, or your doctor’s office may contact you by phone. Test results may also be available through an online health portal. With home test kits, the results are also usually available through a secure online platform. The company may ask you to open an account that allows the lab to notify you when your sample is received, and the results are ready.
Interpreting test results
Your results will list the findings for each particular thyroid hormone. It may include reference ranges for normal results or indicate if your results in each category are normal or abnormal.
Reference ranges for each thyroid hormone differ based on your age, health status, and the laboratory that performs the testing. The American Board of Internal Medicine’s reference ranges for each part of the thyroid panel are listed below:
- TSH: 0.5 to 4 mIU/L
- Free T4: 0.8 to 1.8 ng/dL in adults.
- Total T3: 80 to 180 ng/dL
Because this is a panel test, the results are generally interpreted together. Although TSH is the primary indicator of thyroid function, free T4, and total T3 values help doctors understand the severity of thyroid disorders. If you have normal TSH values you may have abnormal T3 and/or T4 values associated with conditions unrelated to the thyroid.
Keep in mind the thyroid panel is an important part of the diagnostic process but cannot alone conclusively diagnose a thyroid condition. With abnormal results, your doctor can best explain the specific findings and their meaning in your situation.
The following table summarizes some examples of typical test results and their potential meaning for thyroid function.
| TSH | Free T4 | Total or Free T3 | Thyroid Function |
|---|---|---|---|
| Normal | Normal | Normal | Normal thyroid function |
| Normal | Normal or low | Normal or low | Normal thyroid function |
| Normal | Low | Normal or high | Normal thyroid function |
| High | Low | Normal or low | Primary hypothyroidism |
| High | Normal | Normal | Subclinical hypothyroidism |
| Low | High or normal | High | Hyperthyroidism |
| Low | Normal | Normal | Subclinical hyperthyroidism |
Sources
American Board of Internal Medicine. ABIM Laboratory Test Reference Ranges. Updated January 2022. Accessed December 6, 2022. https://www.abim.org/Media/bfijryql/laboratory-reference-ranges.pdf
Columbia Surgery. At-Home Thyroid Testing Kits: What We Know…and What We Don’t: An Interview with Dr. Hyesoo Lowe. Date unknown. Accessed December 6, 2022. https://columbiasurgery.org/news/home-thyroid-testing-kits-what-we-knowand-what-we-dont
National Institute of Diabetes and Digestive and Kidney Diseases. Thyroid Tests. Updated May 2017. Accessed December 6, 2022. https://www.niddk.nih.gov/health-information/diagnostic-tests/thyroid
Ross DS. Diagnosis of Hyperthyroidism. In: Cooper DS, ed. UpToDate. Updated February 15, 2022. Accessed December 6, 2022. https://www.uptodate.com/contents/diagnosis-of-hyperthyroidism
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Ross DS. Laboratory Assessment of Thyroid Function. In: Cooper DS, ed. UpToDate. Updated June 14, 2022. Accessed December 6, 2022. https://www.uptodate.com/contents/laboratory-assessment-of-thyroid-function
Ross DS. Treatment of Primary Hypothyroidism in Adults. In: Cooper DS, ed. UpToDate. Updated April 28, 2022. Accessed December 6, 2022. https://www.uptodate.com/contents/treatment-of-primary-hypothyroidism-in-adults
U.S. Preventive Services Task Force. Thyroid Dysfunction: Screening. Published March 24, 2015. Accessed December 6, 2022. https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/thyroid-dysfunction-screening
