Table of ContentsView AllTable of ContentsPurpose of TestRisks and ContraindicationsBefore the TestAfter the TestInterpreting Results
Table of ContentsView All
View All
Table of Contents
Purpose of Test
Risks and Contraindications
Before the Test
After the Test
Interpreting Results
The T3 test simply measures how much of this hormone is present in your blood. If the level is either abnormally high or abnormally low, it can be an indicator of thyroid disease. However, this test is generally more useful for diagnosinghyperthyroidism(overactive thyroid) thanhypothyroidism(underactive thyroid), and it’s typically combined with measures of other thyroid hormone levels rather than taken alone.
Thethyroidis a butterfly-shaped gland in the front of your throat. It makes hormones and regulates numerous things, including your body’s energy use, body temperature, weight, and mood.
T3 exists in your body in two different forms:
The total T3 test looks at free t3 and bound T3 forms. Your healthcare provider may choose to perform a separate test for free T3.
Total T3 tests are generally ordered when you have symptoms that are consistent with thyroid disease, especially if you have an elevated risk, such as having family members who are diagnosed with thyroid disorders, age, and sex. Hypothyroidism is more common in females over 60, while hyperthyroidism is more common in female age 20 to 40.
Your healthcare provider will likely order other measurements of thyroid function at the same time as T3 test including tests of thyroid stimulating hormone (TSH) and T4. Tests to look for antibodies that indicate autoimmune thyroid disease, includingHashimoto’s thyroiditisandGraves' disease.
The T3 test, as well as other thyroid tests, are performed on blood samples. The process for drawing blood for these tests is generally quick, simple, and low-risk.
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If you’ve had negative reactions to past blood draws, it may be safest to arrange for someone to drive you to and from the test facility.
Let the person who’s drawing your blood know before the test if you have a history of bad reactions to blood draws, you have a bleeding disorder or are taking medications that thin your blood, and/or your skin bruises or tears easily. They should be able to mitigate any risk these factors create.
Blood for T3 and other thyroid tests can generally be drawn at any time of day. Unless other tests that do require fasting are ordered at the same time, it shouldn’t matter when you’ve eaten last.
When you arrive for the test, be sure to have your insurance card and any written orders your healthcare provider may have given you.
Some medications can interfere with thyroid hormone levels and test results. Talk to your healthcare provider about whether you need to take a break from any medications prior to the test.
Known problem medications include:
Other drugs and supplements may impact your results as well, so be sure your healthcare provider knows about everything you’re taking.
Since pregnancy can also affect your thyroid-hormone levels, make sure your healthcare provider knows if you are or could be pregnant.
Timing and Location
The blood draw itself shouldn’t take more than a few minutes. If you’re getting a lot of tests done, it could take slightly longer. Some healthcare provider’s offices may perform the blood draw in conjunction with an appointment. In that case, it should add very little time to the appointment length.
Going to a lab for the test can take more time. If you have a scheduled appointment for your test, be sure to arrive early enough to check in and take care of any co-pays that may be due. If you’re nervous about the test, you may also want to give yourself a few minutes to sit and relax.
Labs are often busy and wait times may vary. If you’re dropping in, it can be a good idea to call ahead of time. Certain times of day, especially first thing in the morning, may be better than others.
What to Wear
You should be able to stay in your own clothing during the test. Your arm will need to be exposed, so short sleeves or those that can easily be pushed up above your elbow will work best.
In case you have a dizzy spell, flat shoes and clothing that is not tight or constrictive may be good choices.
Food and Drink
Any time you’re having blood drawn, you should be sure you’re well hydrated. It will make your veins easier to find and help avoid problems with needle insertion.
Since you don’t need to fast before a T3 test, it’s a good idea to have something in your stomach. It may help you avoid becoming nauseous.
Remember that other tests ordered at the same time may require fasting or other special instructions. Be sure to follow all of the instructions you’re given to ensure accurate test results.
Cost and Health Insurance
Laboratory costs for a total T3 test can range from $35 to around $100. If you’re not insured, you may face additional charges on top of that, especially if your healthcare provider is ordering more than one test. A full set of thyroid tests may cost $500 or more.
Your healthcare provider’s office, insurance company, and the lab should be able to help you determine what it’ll cost before you get the tests.
During the Test
Pre-Test
Once you’ve exposed your arm, the insertion area will be cleaned with alcohol. The nurse or phlebotomist will tie a band around your upper arm to trap your blood and get your veins to stand out. You may be asked to pump your fist to help with this process.
Throughout the Test
Once they identify a good vein, they’ll insert the needle, which will probably cause a little bit of pain upon insertion (but this shouldn’t last long). They’ll then release the band to get the blood flowing again, and the vial attached to the needle should fill up. Depending on how many tests are ordered, they may need to change vials one or more times.
After enough blood has been drawn, they’ll withdraw the needle and put a bandage over the insertion site.
Post-Test
Most of the time, you can leave right away after your blood is drawn.
If you have any kind of negative reaction, let someone at the facility know so they can take care of you properly. Usually, even with a bad reaction, it only takes a few minutes of rest to be okay to leave.
You may notice a little tenderness and possibly bruising around the site where the needle was inserted, which typically goes away quickly. If you have any problems or questions, contact your healthcare provider.
Managing Side Effects
If the site is noticeably sore, you can ice it or take over-the-counter pain medication. You shouldn’t have any other lingering effects.
The normal ranges for adults are generally considered to be:
It’s important to note that not every lab uses the same ranges or measurements.
A high T3 level may indicate:
High T3 can also be due to pregnancy or the use of medications containing estrogen.
An abnormally low T3 level may indicate:
Keep in mind that this test has some limitations, which are that:
Therefore, most healthcare providers today rely on the free T3 blood test instead of the total T3 blood test.
Once your results are in, your healthcare provider may want you to make an appointment to discuss further testing or treatment options, depending on whether a diagnosis has been made.
If you don’t hear back about your results for a long time, or if you don’t understand your results, contact your healthcare provider’s office. If you are diagnosed with a thyroid disorder, then it’s time to start discussing yourtreatment optionswith your practitioner.
A Word From Verywell
Understanding Thyroid Test Results
3 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Mount Sinai.T3 Test.American Thyroid Association.Thyroid Function Tests.MedlinePlus.Triiodothyronine (T3) tests.Additional ReadingJonklaas J, Sathasivam A, Wang H, Gu J, Burman KD, Soldin SJ.Total and free thyroxine and triiodothyronine: Measurement discrepancies, particularly in inpatients.Clinical Biochemistry.2014;47(13-14):1272-1278. doi:10.1016/j.clinbiochem.2014.06.007Kang MG, Hahm JR, Kim K-H, et al.Prognostic value of total triiodothyronine and free thyroxine levels for the heart failure in patients with acute myocardial infarction.The Korean Journal of Internal Medicine.2018;33(3):512-521. doi:10.3904/kjim.2016.292Wang C-Y, Yu T-Y, Shih S-R, Huang K-C, Chang T-C.Low total and free triiodothyronine levels are associated with insulin resistance in non-diabetic individuals.Scientific Reports. 2018;8(1). doi:10.1038/s41598-018-29087-1Welsh KJ, Soldin SJ.DIAGNOSIS OF ENDOCRINE DISEASE: How reliable are free thyroid and total T3 hormone assays?European Journal of Endocrinology.2016;175(6):R255-R263. doi:10.1530/eje-16-0193
3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Mount Sinai.T3 Test.American Thyroid Association.Thyroid Function Tests.MedlinePlus.Triiodothyronine (T3) tests.Additional ReadingJonklaas J, Sathasivam A, Wang H, Gu J, Burman KD, Soldin SJ.Total and free thyroxine and triiodothyronine: Measurement discrepancies, particularly in inpatients.Clinical Biochemistry.2014;47(13-14):1272-1278. doi:10.1016/j.clinbiochem.2014.06.007Kang MG, Hahm JR, Kim K-H, et al.Prognostic value of total triiodothyronine and free thyroxine levels for the heart failure in patients with acute myocardial infarction.The Korean Journal of Internal Medicine.2018;33(3):512-521. doi:10.3904/kjim.2016.292Wang C-Y, Yu T-Y, Shih S-R, Huang K-C, Chang T-C.Low total and free triiodothyronine levels are associated with insulin resistance in non-diabetic individuals.Scientific Reports. 2018;8(1). doi:10.1038/s41598-018-29087-1Welsh KJ, Soldin SJ.DIAGNOSIS OF ENDOCRINE DISEASE: How reliable are free thyroid and total T3 hormone assays?European Journal of Endocrinology.2016;175(6):R255-R263. doi:10.1530/eje-16-0193
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Mount Sinai.T3 Test.American Thyroid Association.Thyroid Function Tests.MedlinePlus.Triiodothyronine (T3) tests.
Mount Sinai.T3 Test.
American Thyroid Association.Thyroid Function Tests.
MedlinePlus.Triiodothyronine (T3) tests.
Jonklaas J, Sathasivam A, Wang H, Gu J, Burman KD, Soldin SJ.Total and free thyroxine and triiodothyronine: Measurement discrepancies, particularly in inpatients.Clinical Biochemistry.2014;47(13-14):1272-1278. doi:10.1016/j.clinbiochem.2014.06.007Kang MG, Hahm JR, Kim K-H, et al.Prognostic value of total triiodothyronine and free thyroxine levels for the heart failure in patients with acute myocardial infarction.The Korean Journal of Internal Medicine.2018;33(3):512-521. doi:10.3904/kjim.2016.292Wang C-Y, Yu T-Y, Shih S-R, Huang K-C, Chang T-C.Low total and free triiodothyronine levels are associated with insulin resistance in non-diabetic individuals.Scientific Reports. 2018;8(1). doi:10.1038/s41598-018-29087-1Welsh KJ, Soldin SJ.DIAGNOSIS OF ENDOCRINE DISEASE: How reliable are free thyroid and total T3 hormone assays?European Journal of Endocrinology.2016;175(6):R255-R263. doi:10.1530/eje-16-0193
Jonklaas J, Sathasivam A, Wang H, Gu J, Burman KD, Soldin SJ.Total and free thyroxine and triiodothyronine: Measurement discrepancies, particularly in inpatients.Clinical Biochemistry.2014;47(13-14):1272-1278. doi:10.1016/j.clinbiochem.2014.06.007
Kang MG, Hahm JR, Kim K-H, et al.Prognostic value of total triiodothyronine and free thyroxine levels for the heart failure in patients with acute myocardial infarction.The Korean Journal of Internal Medicine.2018;33(3):512-521. doi:10.3904/kjim.2016.292
Wang C-Y, Yu T-Y, Shih S-R, Huang K-C, Chang T-C.Low total and free triiodothyronine levels are associated with insulin resistance in non-diabetic individuals.Scientific Reports. 2018;8(1). doi:10.1038/s41598-018-29087-1
Welsh KJ, Soldin SJ.DIAGNOSIS OF ENDOCRINE DISEASE: How reliable are free thyroid and total T3 hormone assays?European Journal of Endocrinology.2016;175(6):R255-R263. doi:10.1530/eje-16-0193
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