This material must not be used for commercial purposes, or in any hospital or medical facility. Failure to comply may result in legal action.
What is it?
T4, also called thyroxine (thi-rocks-een), is a hormone released by the thyroid gland. The thyroid gland is located in the front part of your neck. A hormone is a substance made by one organ in your body. The hormone travels in the blood to another organ to help the other organ work. The T4 hormone can be measured in your blood by a special laboratory test. The results of this test help your caregiver find if your thyroid gland is working OK.
Why do I need it?
Your good health depends on a thyroid gland that is working OK. The thyroid hormones have an effect on most cells in your body. Other thyroid tests may be done at the same time as the T4. If you are taking thyroid medicines, this test may be needed to see how the medicines are working. Your caregiver may want you to have this test if you have symptoms of hyperthyroidism (hi-per-thi-roid-is-um) or hypothyroidism (hi-po-thi-roid-is-um). Hyperthyroidism means you have too much thyroid hormone. Hypothyroidism means you do not have enough thyroid hormone.
What are the symptoms of hyperthyroidism?
Some of the hyperthyroidism symptoms may include:
- Weight loss.
- Nervousness, tremors.
- Bulging eyes.
- Swelling in the front of your neck.
- Feeling hot all the time, sweating.
- Irregular heart beat.
What are the symptoms of hypothyroidism?
Some of the hypothyroidism symptoms may include:
- Weight gain.
- Being tired or sleepy.
- Not able to think clearly.
- Dry skin and hair.
- Loss of hair over your whole body, not just your head.
- Feeling cold all the time.
How do I get ready for the test?
Your caregiver will tell you when to have your blood test done. The blood test may be done before or after eating. Some medicines interfere with this test. Ask your caregiver if you should wait to take your medicines until after your blood is taken.
How is the specimen collected?
A caregiver will put a wide rubber strap around your arm and tighten it. Your skin will be cleaned with alcohol. A small needle attached to a special test tube will be put into a vein in your arm or hand. The tube has suction to pull the blood into it. When the tube is full, the rubber strap, needle and tube are removed. The caregiver will press a piece of cotton where the needle was removed. You may be asked to hold the cotton on the site for a few minutes to help stop the bleeding. Tape may then be put over the cotton on your arm.
What do I do after the test?
You may remove the tape and cotton in about 20 to 30 minutes. Call your caregiver to get the results of your test. Your caregiver will explain what your test results mean for you. Follow the instructions of your caregiver.
You have the right to help plan your care. To help with this plan, you must learn about your lab tests. You can then discuss the results with your caregivers. Work with them to decide what care may be used to treat you. You always have the right to refuse treatment.
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.