Thyroid hormone that isn’t bound to TBG is called “free” T3 or T4.
This test doesn’t paint a complete picture of thyroid function (or any other disease or condition).
Thus, the total thyroid hormone level will be elevated even though the person does not have hyperthyroidism.
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Ablood drawis a simple, routine procedure that carries very little risk.
If this happens to you, tell the person drawing your blood.
They’ll likely have you drink some water and lie down for a few minutes.
If not, any time of the day should be fine.
The blood draw itself should only take a few minutes.
Food and Drink
Fasting isn’t typically required for a TBG test.
Dehydration can make needle insertion harder.
Available pricing information ranges from $80 to about $150.
What to Bring
If your healthcare provider gave you written orders, take them with you.
Also, be sure you have a current insurance card with you.
Some facilities may ask for valid identification, such as a driver’s license, as well.
During the Test
Typically, your blood will be drawn by a nurse or phlebotomist.
This is to help avoid mistakes.
If your veins don’t stand out well, you may be asked to pump your fist.
Throughout the Test
Once a good vein is found, the needle will be inserted.
It might hurt for a couple of seconds.
The band will be released to get the blood flowing into the vial attached to the needle.
Depending on how many tests are ordered, you may need to fill up two or more vials.
After enough blood has been drawn, the needle will be withdrawn and the insertion site will be bandaged.
Post-Test
Most of the time, you could leave right after the test is over.
If you have any kind of negative reaction, speak up so you could get the proper care.
Usually, even with a bad reaction, people are OK after a few minutes.
If you have any problems or questions, contact your healthcare provider’s office.
Managing Side Effects
Ice or over-the-counter pain medications can help if you have any pain or inflammation.
You shouldn’t have any other lingering effects.
Interpreting Results
Results depend on which technique the laboratory uses to evaluate your blood sample.
Electrophoresis:In this method, an electrical current is run through your blood serum.
Normal results from this method range from 10 to 24 milligrams (mg)/100 milliliters (mL).
The normal range from this method is from 1.3 to 2.0 mg/100mL.
If TBG results are normal but thyroid hormone levels are low, the diagnosis is typically hypothyroidism.
If TBG is normal but thyroid hormone levels are high, the likely diagnosis is hyperthyroidism.
University of California San Francisco Health.Serum TBG level.
2013;52(4):287-96. doi:10.1177/0009922813475706
American Thyroid Association.Thyroiditis.
Cleveland Clinic.Thyroid blood tests.
