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Is Fasting Required For Thyroid Blood Test

What Are Thyroid Blood Tests And Why Are They Taken

Do you have to Fasting for Thyroid Blood Tests? |Thyroid Series| Dr.Ravi Sankar | Hi9

Thyroid blood tests are used to tell if your thyroid gland is functioning properly by measuring the amount of thyroid hormones in your blood. They are done by withdrawing blood from a vein in your arm. These blood tests help to diagnose thyroid diseases.

The thyroid is a butterfly-shaped gland located in the front part of your neck. Its job is to produce thyroid hormones, which travel through your bloodstream and regulate many aspects of your bodys metabolism, including temperature, weight, and energy.

Thyroid blood tests show if you have:

  • Hyperthyroidism: Overactive thyroid producing more thyroid hormones than your body needs. Hyperthyroidism speeds up your metabolism, which can cause weight loss, rapid heartbeat, insomnia, puffiness around the eyes, anxiety and other symptoms. The most common cause of hyperthyroidism is Graves disease.
  • Hypothyroidism: Underactive thyroid producing too few thyroid hormones. Hypothyroidism slows down your metabolism, which can cause weight gain, menstrual irregularity, dry and puffy skin, fatigue and other symptoms. The most common cause of hypothyroidism is Hashimotos disease.

Thyroid blood tests are used to diagnose thyroid disorders associated with hyper- or hypothyroidism. These include:

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  • TSH– This is a pituitary hormone that responds to low/high amounts of circulating thyroid hormone. In advanced cases of Hashimoto’s and primary hypothyroidism, this lab test will be elevated. In the case of Graves’ disease the TSH will be low. People with Hashimoto’s and central hypothyroidism may have a normal reading on this test.
  • Free T3 & Free T4-These tests measure the levels of active thyroid hormone circulating in the body. When these levels are low, but your TSH tests in the normal range, this may lead your physician to suspect a rare type of hypothyroidism, known as central hypothyroidism.

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 youre taking any medication or if you may be pregnant. This may alter the results of your test.

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What Is Reverse T3

Reverse T3 is a biologically inactive form of T3. Normally, when T4 is converted to T3 in the body, a certain percentage of the T3 is in the form of RT3. When the body is under stress, such as during a serious illness, thyroid hormone levels may be outside of normal ranges even though there is no thyroid disease present. RT3 may be elevated in non-thyroidal conditions, particularly the stress of illness. It is generally recommended that thyroid testing be avoided in hospitalized patients or deferred until after a person has recovered from an acute illness. Use of the RT3 test remains controversial, and it is not widely requested.

Thyroid Blood Test Procedure

What You Need To Know About Doing Thyroid TSH Blood Tests
  • Your doctor will first note down your entire case history to understand if you need a thyroid blood test.
  • You will be asked to withhold any drugs or medications for 6-8 hours before the drawing blood for a thyroid test as they may interfere with test results.
  • You will be asked to roll up your sleeve and the nurse will tie a tourniquet around your arm so that your veins swell and become prominent.
  • The nurse or laboratory technician will puncture a vein to draw blood.
  • Blood is stored in a plain bulb and sent to the laboratory for investigation.
  • Testing for only thyroid stimulating hormone does not require fasting and can be done at any time of the day. TSH levels observed in the fasting state are about 26% higher than in the non-fasting state.
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    What Should I Do To Prepare For A Thyroid Function Test

    Thyroid function tests usually require very little preparation.

    You don’t need to fast before the blood test. And it doesn’t matter if you have taken your thyroid medicine just before the blood test.

    Tell your doctor if you are taking any medication, as some medicines can alter the test results and how they are interpreted.

    It is also important to mention if you have had any X-ray tests that have used a special contrast dye, as this may contain iodine which can affect the results. Levels of thyroid chemicals also change in pregnancy, so tell your doctor if you are pregnant when the test is taken.

    Note: all newborn children have their thyroid function tested as part of the heel prick test which is offered to all babies and undertaken when they are 5 days old. See the separate leaflet called Newborn Baby Screening Tests for more information.

    When Do I Need A Thyroid Test

    One may need a thyroid test if you think you have symptoms of underactive or overactive thyroid gland. Having excessive thyroid hormones in your blood is called hyperthyroidism and insufficient thyroid hormones is known as hypothyroidism.

    Symptoms of hypothyroidism include following:

    • Weight gain
    • Diarrhea

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    What Blood Tests Are Done To Test The Thyroid

    Thyroid blood tests include:

    These tests alone arent meant to diagnose any illness but may prompt your healthcare provider to do additional testing to evaluate for a possible thyroid disorder.

    Additional blood tests might include:

    • Thyroid antibodies: These tests help identify different types of autoimmune thyroid conditions. Common thyroid antibody tests include microsomal antibodies , thyroglobulin antibodies , and thyroid receptor antibodies .
    • Calcitonin: This test is used to diagnose C-cell hyperplasia and medullary thyroid cancer, both of which are rare thyroid disorders.
    • Thyroglobulin: This test is used to diagnose thyroiditis and to monitor treatment of thyroid cancer.

    Do You Follow These Tips When You Have Blood Drawn

    Can Keto & Fasting Heal Your Thyroid Condition?

    See also:

    The book Be Your Own Thyroid Advocate: When Youre Sick and Tired of Being Sick and Tired, which builds on this article in detail and explains how to thrive with thyroid disease.

    You can click on the hyperlinks in the above article to learn more and see references to information given, as well as the below links.

    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5167556/

    https://in.bgu.ac.il/en/fohs/communityhealth/Family/Documents/HYPOTHYROIDISM%20Guidelines%20ATA%20AACE%202012.pdf

    Adult Hypothyroidism

    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4171896/

    http://www.schizophrenia.com/sznews/archives/004348.html#

    If you found this article beneficial, please take a moment to share it so we can help others get better with hypothyroidism and Hashimoto’s, whilst also raising awareness.

    Rachel Hill is the highly ranked and multi-award winning thyroid patient advocate, writer, speaker and author behind The Invisible Hypothyroidism. Her thyroid advocacy work includes writing articles, authoring books, producing her Thyroid Family email newsletters and speaking on podcasts, as well as being a founding board member for the American College of Thyroidology. She is well-recognised as a crucial contributor to the thyroid community and has a large social media presence. Her books include Be Your Own Thyroid Advocate and You, Me and Hypothyroidism.

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    Why Do Some Blood Tests Require Fasting

    Certain blood tests require you to fast for 8-12 hours. The reason for asking you to fast is because when eat or drink beverages, certain nutrients, substances or vitamins enter into the bloodstream and can be responsible for giving a wrong result. Fasting before these advised blood tests ensures more accurate results.

    Certain blood tests require you to not even drink water. Otherwise, drinking normal water will keep you hydrated and prevent your veins from collapsing, so drawing blood becomes easier since your veins are visible.

    Avoid food, alcohol, soda or aerated drinks, tea, coffee, chewing gums and even exercising while fasting.

    You need to consult your physician if you can take your regular dose of medications during fasting or adjust the dose timings for the purpose of fasting. This is because certain drugs can alter test results.

    How Is The Test Used

    A thyroid panel may be used to evaluate thyroid function and/or help diagnose thyroid disorders.

    Typically, the preferred initial test for thyroid disorders is a TSH test. If the TSH level is abnormal, it will usually be followed up with a test for free T4. Sometimes a total T3 or free T3 will also be performed. Often, the laboratory will do this follow-up testing automatically. This is known as reflex testing and it saves the healthcare practitioner time from having to wait for the results of the initial test and then requesting additional testing to confirm or clarify a diagnosis. Reflex tests are typically performed on the original sample that was submitted when the initial test was requested.

    As an alternative, a thyroid panel may be requested by your healthcare practitioner. This means that all three tests will be performed at the same time to get a more complete initial picture of thyroid function.

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    Does Menstruation Affect Testing

    Generally, being on your period when having a thyroid test conducted isnt known to cause any issues or affect results, but if youre feeling particularly unwell from your period then you may wish to have blood drawn when you feel better. Especially if you already lose a lot of blood with menstruation. Heavy periods can be a symptom of hypothyroidism.

    What Is A Thyroid

    Is Fasting Required For Thyroid Test

    Your thyroid is a small gland found at the front of your windpipe . It produces two hormones that help control your metabolism the chemical processes that occur in your body that keep you alive, like breathing and breaking down food into energy. These hormones are called triiodothyronine and thyroxine .

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    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 hypothyroidismwhich is diagnosed specifically by looking at TSH levels.

    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 Adams 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 its a normal size, it cannot be felt however, when it doesnt work right, it may become enlarged or could grow lumps of extra tissue.

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    Is There Anything Else I Should Know

    In the past, panels of tests were more common. More recently, however, the practice has been to order, where possible, one initial or screening test and then follow up with additional testing, if needed, to reduce the number of unnecessary tests. With thyroid testing, one strategy is to screen with a TSH test and then order additional tests if the results are abnormal or if clinical suspicions warrant.

    Your thyroid hormone test results can be affected by:

    • Increases, decreases, and changes in the proteins that bind T4 and T3
    • Pregnancy

    T3 Resin Uptake Results

    Intermittent Fasting For Thyroid Health?

    A T3 resin uptake, also known as a T3RU, is a blood test that measures the binding capacity of a hormone called thyroxin-binding globulin . If your T3 level is elevated, your TBG binding capacity should be low.

    Abnormally low levels of TBG often indicate a problem with the kidneys or with the body not getting enough protein. Abnormally high levels of TBG suggest high levels of estrogen in the body. High estrogen levels may be caused by pregnancy, eating estrogen-rich foods, obesity, or hormone replacement therapy.

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    Do I Have To Fast For A Thyroid Blood Test

    Studies have shown that early morning fasting causes higher TSH levels compared to tests taken in the afternoon on patients that did not fast. Since fasting affect TSH levels, fasting might make it difficult to diagnose subclinical hypothyroidism, as the condition is diagnosed by specifically looking at TSH levels.5 Ask your healthcare provider whether you should fast before taking your thyroid blood test.

    1. ADAM. “Everything That You Need To Know Before Getting A Full Thyroid Panel.” ThyroMate. ThyroMate.com, April 25, 2017, . Accessed April 3, 2018.

    2. Luo, Elaine K. “Thyroid Function Tests.” healthline. Healthline Media, February 27, 2018, . Accessed April 3, 2018.

    3. Mayo Clinic Staff. “Hypothyroidism .” MayoClinic.org. . Published December 6, 2017. Accessed April 3, 2018.

    4. Northrup, Christiane. “What is Thyroid Disease? Common Thyroid Disease Symptoms To Look For.” Christiane Northrup, M.D. Christiane Northrup, October 24, 2017, . Accessed April 3, 2018.

    7. “Thyroid Blood Tests.” Cleveland Clinic. The Cleveland Clinic Foundation, . Accessed April 3, 2018.

    Non Fasting Blood Test Lists:

    Non-fasting blood tests are those tests which their readings dont obviously affected by foods or drinks, it means theyre tested randomly at any time during the whole day.

    • A1C test is not requiring a fasting period prior to sampling because it depends on glucose particles attached to RBCs surface and not depends on the circulating glucose.
    • CBC blood test is not requiring a fasting period prior testing because it is only counts the blood cells, blood cells count not affected by food type in general.
    • Thyroid function tests does not need fasting period, because thyroid hormone is responsible for metabolism processes, hence T4 and T3 is not a fasting blood test.
    • TSH blood test isnt a fasting blood test.
    • PSA blood test fasting is not needed, you dont have to fast from foods and drinking before taking prostate specific antigen test, as no study yet to told us about influence of PSA levels by some foods, however high PSA medications are responsible for lowering PSA levels, so that consult your urologist when testing PSA with taking its medications.
    • Blood group type and RH tests does not require fasting before identify the ones blood type.
    • Cancer antigens blood tests are not fasting tests in general, when testing for Cancer antigen CA.19.9, it is preferred to fast

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    Is Fasting Required For Tft Blood Test

    4.8/5fastingtestsfastfastingfasting

    Similarly, is fasting required for thyroid test?

    Fasting. A diagnosis of subclinical hypothyroidism may be missed if you get your blood test when your TSH value is at its lowest of the day due to a non-fasting afternoon blood draw.

    Also, what time of day is best for thyroid test? Current research suggests that TSH serum levels peak at between 2 am and 4 am and decrease to their lowest levels at between 4 pm and 8 pm. Thus, the lower afternoon TSH levels found in the current abstract are consistent with previous research.

    Considering this, can you eat or drink before a blood test for thyroid?

    You don’t need any special preparations for a TSH blood test. If your health care provider has ordered other blood tests, you may need to fast for several hours before the test.

    Can you drink coffee before a thyroid blood test?

    Drinking coffee within 60 minutes of taking your thyroid hormone reduces absorption. Badness associated with high cortisol. They obsessively check your Thyroid Stimulating Hormone , which may or may not reflect the cortisol hijack of your thyroid hormones.

    What Do My Thyroid Test Results Mean

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

    The T4 testmore commonly known as the thyroxine testis 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 youve 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 Graves 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.

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

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    When Is It Ordered

    A thyroid panel may be ordered when you have signs and symptoms that suggest underactive thyroid or overactive thyroid due to a thyroid disorder.

    Signs and symptoms of an underactive thyroid may include:

  • Slowed heart rate
    • Trouble tolerating heat
    • Sometimes more frequent bowel movements
    • Some uncommon problems that can affect the eyes: puffiness around the eyes, dryness, irritation, excessive tearing, light sensitivity, blurry double vision
    • In some cases, bulging of the eyes
    • Less frequent or lighter menstrual periods in women

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