Who performs a T4 (thyroxine) blood test?

A phlebotomist usually performs blood draws, including those for a T4 blood test, but any healthcare provider who is trained in drawing blood can perform this task. They then send the samples to a lab where a medical laboratory scientist prepares the samples and performs the tests on machines known as analyzers.

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You usually don’t need to do anything special for a T4 test. Depending on the reason for the test, you may need to stop taking certain medications or supplements. In any case, your healthcare provider will give you specific instructions.

Biotin, an over-the-counter supplement, can cause several thyroid tests to appear abnormal when they are in fact normal. It’s recommended to stop biotin-containing supplements 3 to 5 days before any thyroid-related blood draw to avoid this effect.

You can expect to experience the following during a blood test, or blood draw:

You’ll sit in a chair, and a phlebotomist will check your arms for an easily accessible vein. This is usually in the inner part of your arm on the other side of your elbow.

Once they’ve located a vein, they’ll clean and disinfect the area.

They’ll then insert a small needle into your vein to take a blood sample. This may feel like a small pinch.

After they insert the needle, a small amount of blood will collect in a test tube.

Once they have enough blood to test, they’ll remove the needle and hold a cotton ball or gauze on the site to stop the bleeding.

They’ll place a bandage over the site, and you’ll be finished.

The entire procedure usually takes less than five minutes.

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After a phlebotomist has collected your blood sample, they’ll send it to a laboratory for testing. Once the test results are back, your provider will share the results with you.

Blood tests are a very common and essential part of medical testing and screening. There’s very little risk to having a T4 blood test. You may have slight tenderness or a bruise at the site of the blood draw, but this usually resolves quickly.

In most cases, you should have your T4 test results within one or two business days, though it could take longer.