Do You Need to Fast Before a Thyroid Blood Draw

When most people hear about the thyroid, they associate it with the inability to lose or gain weight, but it is responsible for much more than that.

In fact, hormones made by the thyroid can impact how quickly your heart beats, how deep you breathe, your body temperature, women's menstrual cycles and cholesterol levels.

Unfortunately, more than 12 percent of people will deal with a thyroid problem in their life, with women being more likely to deal with this issue than men.

Here's what you need to know about the thyroid and what a test can detect.

What is the Thyroid?

Located on the lower part of the front of the neck, the thyroid is a butterfly-shaped gland that measures two inches in length. For men, the gland is located underneath the Adam's apple, near the windpipe.

The thyroid, which is part of the endocrine system, is responsible for the metabolism.

When there are no issues with the thyroid, and it's a normal size, it cannot be felt; however, when it doesn't work right, it may become enlarged or could grow lumps of extra tissue.

What are Thyroid Function Tests?

If your doctor suspects you are having problems with your thyroid, he or she may recommend a thyroid function test.

These simple blood tests are used to determine how well your thyroid gland is working based on your hormone levels.

There are four different types of thyroid function tests: T3, T3RU, T4 and TSH.

If your doctor is concerned about the levels of your hormones, broad screening tests, like the T4 or the TSH test will be ordered.

Further tests may be needed to help determine what's going on if the results of these tests come back abnormal.

How are Thyroid Tests Done?

In order to properly test the hormone levels of your thyroid, a blood draw will be performed by your doctor or at a lab.

Prior to the blood draw, you will be asked to sit in a chair, roll up your sleeves and relax while a nurse or technician prepares your arm for the draw.

A band of rubber will be tightly tied around your upper arm to force the veins to swell. This makes it easier for a vein to be found so the needle can be inserted.

Having blood drawn is mostly painless, although it is possible to feel a sharp prick when the needle is inserted. This is typically a very quick sensation.

Once the blood has been fully drawn, the needle will be removed and a small bandage will be placed over your wound.

Before your tests are performed, you should tell your doctor if you're taking any medication or if you may be pregnant. This may alter the results of your test.

Is Fasting Required for a Thyroid Test?

Most doctors will suggest you do not fast before your thyroid function test.

Research shows that fasting, especially early in the morning, may impact TSH levels. A fasting test typically results in higher TSH levels versus one done in the afternoon.

Because fasting causes higher TSH levels, it can make it hard to properly diagnose hypothyroidism—which is diagnosed specifically by looking at TSH levels.

What Do My Thyroid Test Results Mean?

The two most common types of thyroid function tests are the T4 and TSH test. Typically, these two tests are ordered together.

The T4 test—more commonly known as the thyroxine test—is used to determine if your thyroid is overactive. If this is the case, you will be diagnosed with hyperthyroidism.

Symptoms of hyperthyroidism include unplanned weight loss, tremors, diarrhea and anxiety.

The TSH test will reveal how much thyroid-stimulating hormone is in your blood. Normal levels range from 0.4 to 4.0 milli-international units of hormone per liter of blood.

If you've been diagnosed with hyperthyroidism and your TSH levels are above 2.0 mIU/L, you are at a heightened risk of developing hypothyroidism, which can result in weight gain, fatigue, depression and weak hair and nails.

If your doctor believes you have hyperthyroidism, he or she may order a T3 test to check for levels of the hormone triiodothyronine.

This hormone level should be within 100-200 nanograms of hormone per deciliter of blood. If your levels are abnormally high, it is possible that you are suffering from an autoimmune disorder called Grave's disease.

The final thyroid function test your doctor may order is the T3 resin uptake test. Also known as a T3RU, this blood test will measure the binding capacity of a hormone called thyroxin-binding globulin.

When levels of T3 are low, it may be an indication you have kidney problems or your body is not getting the protein is needs. High levels, on the other hand, can reveal an abnormally high level of estrogen in the body.

Your doctor's office should reach out to you within a matter of days to walk you through the results of your thyroid test.

In some cases, an ultrasound test may be recommended to check for structural problems, thyroid gland activity and tumors that could be causing an issue. Your doctor may also want to take a sample of tissue from your thyroid to test for cancer,

If you are showing signs of a thyroid problem, such as irritability, anxiety, depression, difficulty sleeping or unintentional weight loss or gain, it's important that you see a doctor as soon as possible.

You should also seek medical care if you feel a growth on your thyroid gland or notice swelling.

CareNow Can Help

With more than 100 clinics throughout the United States, CareNow® is your go-to spot for any urgent care needs, including thyroid function testing.

Each CareNow® clinic is open after hours and on the weekend, so you can get the answers you need whenever you need them.

Because CareNow® is all about convenient service, be sure to take advantage of the Web Check-In® feature to avoid the waiting room.

Disclaimer: Patients' health can vary. Always consult with a medical professional before taking medication, making health-related decisions or deciding if medical advice is right for you.

Do You Need to Fast Before a Thyroid Blood Draw

Source: https://www.carenow.com/blog/entry/what-can-a-thyroid-test-detect#:~:text=Most%20doctors%20will%20suggest%20you,one%20done%20in%20the%20afternoon.

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