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Do You Have To Fast For A Thyroid Blood Test

Thyroid Blood Test Procedure

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

Regardless of the type of thyroid function blood test you undergo, they all involve taking a blood draw in a doctor’s office. Studies have shown that patients who partake in early morning fasting have higher TSH levels than afternoon patients who do not fast.5

Certain medication can affect your thyroid blood test results, including:5

  • Those that cause hypothyroidism, such as iodine supplements, lithium, tyrosine kinase inhibitors, and immunomodulating drugs like interferon alpha
  • Those that interfere with thyroid hormone replacement absorption in the gut, like calcium carbonate, iron sulfate, and proton pump inhibitors
  • Those that interfere with lab measurements, but not the thyroid itself, such as certain nonsteroidal anti-inflammatories , heparin, and biotin

Pregnancy and severe illness can also affect thyroid function.5 Before undergoing a thyroid blood test, tell your healthcare provider if you’re taking medication, are pregnant, or have been hospitalized recently.

Is Fasting Required For Thyroid Test And Other Questions Answered

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The thyroid is a small, butterfly-shaped gland. It is located near your throat and makes hormones that play an important role in regulating your weight, body temperature, and even your mood. Primarily, thyroid hormones regulate the way your body uses energy.Having a healthy level of thyroid hormones helps your body perform metabolic functions optimally. Book a thyroid panel and know about your thyroid gland health. Got questions about thyroid tests? Here we are providing answers to some of the most frequently asked questions about thyroid tests:

How To Understand The Results Of Your Thyroid Test

Many at-home test kits provide some level of interpretation within their test results which is usually emailed or found within their online patient portal, says Dr. Shapiro. However, it is still important to pass results on to your physician in order to arrive at a true diagnosis and begin treatment.”

Getting your hormone levels back on track if your test results and physician confirm a thyroid issue is a complex medical process, which is why working with an endocrinologist or other health professional who understands your thyroid is so vital if you do get a result outside of the typical range.

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When To Take Medication

T4-Only Meds

In regards to T4-only medication such as Levothyroxine and Synthroid, they only have a half-life of around five to nine days, which means that once youve become stable on a dose, it takes around a week for half of that dose to clear the body and blood levels to reflect this. This is why, when some people decide to stop taking it, they feel fine for the first week or so.

Therefore, whether you take T4-only medication right before your blood test or blood sample is taken, or havent taken it for up to two days beforehand, your TSH levels and Free T3 levels should still be the same, but free T4 may well show a peak two hours after taking T4 medications.

According to Thyroid Manager:

Serum T4 concentrations peak two to four hours after an oral dose and remain above normal for approximately six hours in patients receiving daily replacement therapy. For this reason, thyroid expert Richard Shames, MD has the following recommendation: I absolutely recommend that patients have any morning blood tests evaluating the thyroid before taking any thyroid medication. I have always told my patients to do it this way.

The American Association of Clinical Endocrinologists and The American Thyroid Associated Guidelines also state:

So, if you were to take your T4-only thyroid medication before a thyroid blood draw, your Free T4 levels could come out elevated, leading to your doctor lowering the medication dosage, when you dont actually need it lowering.

T3 Meds

What Are Thyroid Blood Tests

Do you have to Fasting for Thyroid Blood Tests?

Doctors use blood tests to check for thyroid or pituitary problems. In kids already diagnosed with thyroid or pituitary problems, the tests are used to guide treatment.

Commonly ordered thyroid blood tests include:

  • T4 test: This is done to measure the blood level of the hormone T4 . It might be done in one or both of the following ways:
  • total T4, which measures the entire amount of thyroxine in the blood, including the amount attached to blood proteins that help carry the hormone through the bloodstream
  • free T4, which measures only the thyroxine that’s not attached to proteins. This is the part of T4 in the blood that affects how the body’s cells work.The results of the T4 blood tests can help diagnose hyperthyroidism or hypothyroidism and guide treatment.
  • TSH test: A thyroid stimulating hormone test can help tell how well the thyroid is working. If a thyroid disease prevents the gland from making enough thyroid hormone, the pituitary gland releases more TSH into the blood. If the thyroid is making too much thyroid hormone, the pituitary releases less TSH, which can lower the levels of TSH in the blood.
  • T3 total test: The T3 total test measures the other major thyroid hormone in the blood. It often helps doctors diagnose hyperthyroidism.
  • In some cases, abnormal thyroid test results can be due to a medicine, an ongoing medical condition, or pregnancy. In these cases, there may be nothing wrong with the thyroid or pituitary glands themselves.

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    How Do Thyroid Tests Work

    Thyroid tests use blood samples to check the levels of TSH and T4. If there are any concerning results, more detailed testing can be done, including checking for T3 levels.

    If your levels are too high or low, you may also need an ultrasound to view the structure of your thyroid, since tumors on the thyroid gland can cause symptoms that are similar to hypothyroidism and hyperthyroidism. You may need to go on daily medication to regulate your levels.

    Food and Drug Administration , home test kits, in general, are a suitable way to receive quick and confidential lab results. Theyre not a substitute for receiving regular care from a healthcare professional. A thyroid blood test is only one part of receiving a diagnosis, and for some people, more testing or clinical exams might be necessary.

    Some endocrinologists, or doctors who specialize in hormone-related conditions like thyroid disorders, have concerns about the reliability of thyroid kits and the potential for misdiagnosis. But this is why its still important to inform your healthcare professional of these results.

    There Are Two Things I Know When It Comes To Achieving And Maintaining Good Health: Fasting Is Second To None And Having A Healthy Thyroid Function Is A Must Can Fasting And Thyroid Conditions Coincide

    Fasting and thyroid conditions can be compatible, if done correctly. The thyroid is a small, but extremely important gland in the human body. TheNational Institute of Health describes the thyroid as a 2-inch-long, butterfly-shaped gland weighing less than 1 ounce. Located in the front of the neck below the larynx, or voice box, it has two lobes, one on either side of the windpipe. The thyroid is one of the glands that make up the endocrine system. The glands of the endocrine system produce and store hormones and release them into the bloodstream. The hormones then travel through the body and direct the activity of the bodys cells. Can we fast with thyroid conditions? Lets take a closer look.

    Thyroid conditions can have a tremendous impact on a persons health and are on the rise: Autoimmune thyroid affects millions, and oftentimes goes undiagnosed. According to theNational Cancer Institute, there were 53,990 estimated new cases of thyroid cancer in 2018, with rates for new cases rising on average 3.1% each year over the last 10 years. Death rates have been rising as well, 0.7% each year over 2006-2015.1

    According to the National Institute of Diabetes and Digestive Kidney Diseases, other thyroid conditions are problematic as well: approximately 4.6 percent of the U.S. population ages 12 and over has an underactive thyroid 2, and 1 person out of 100 in the U.S. have an overactive thyroid 3.

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    Lab Tests Of Biopsy Samples

    In some cases, doctors might use molecular tests to look for specific gene changes in the cancer cells. This might be done for different reasons:

    • If FNA biopsy results arent clear, the doctor might order lab tests on the samples to see if there are changes in the BRAF or RET/PTC genes. Finding one of these changes makes thyroid cancer much more likely.
    • For some types of thyroid cancer, molecular tests might be done to see if the cancer cells have changes in certain genes , which could mean that certain targeted drugs might be helpful in treating the cancer.

    These tests can be done on tissue taken during a biopsy or surgery for thyroid cancer. If the biopsy sample is too small and all the molecular tests cant be done, the testing may also be done on blood that is taken from a vein, just like a regular blood draw.

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    Is Fasting Required For A Thyroid Test

    Can Keto & Fasting Heal Your Thyroid Condition?

    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.

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    What You Can Do

    If you have definite symptoms of hypothyroidism, you should talk to your clinician about being tested. If your LDL cholesterol has been advancing or your weight has been creeping up unexplainably, you’ll want to discuss getting a test. If you’re 60 or older and generally healthy, it’s still a good idea to check with your doctor to see whether your medical history suggests you might benefit from testing.

    Image: Thinkstock

    Paloma Health Complete Thyroid Test Kit

    This test screens for TSH, T3, and T4 levels and the presence of thyroid antibodies. Paloma Health states that this test is suitable for people who have received a diagnosis for a thyroid condition or believe they may have one.

    The company offers additional testing for reverse T3 and vitamin D levels. Individuals can add this to their purchase when choosing their test.

    A licensed doctor reviews each test in the United States. Individuals will receive their test results within 1 week of testing.

    Paloma Health states that this test is only available for those who are over 18 years of age. This test is currently not available to those outside the United States, nor is it available to those who live in New Jersey, New York, or Rhode Island.

    FDA advises that people taking any at-home tests should also contact their doctor to discuss any symptoms or test results. At-home testing should not replace regular check-ups with a healthcare professional.

    People experiencing signs and symptoms of hyperthyroidism or hypothyroidism should see a healthcare professional for diagnosis and treatment.

    If a person does not receive treatment for thyroid conditions, they can experience complications. Complications of hyperthyroidism include preeclampsia, premature birth, and miscarriage.

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    What Is The Normal Reference Range For Thyroid Function Tests

    Reference ranges for each value under thyroid hormone is not consistent for everyone. It differs based on certain parameters such as age, health condition, and the laboratory that performs the testing.Common reference ranges for the thyroid panel are enlisted here:

    • TSH: 0.4 to 4.5 mIU/L
    • Free T4: Often falls between 0.8 and 1.5 ng/dL in adults.
    • Total T3: 75 to 195 ng/dL

    Check your test report or ask your doctor for the normal/reference range. Most laboratory reports mention the reference ranges applied to your thyroid test, however, consult an expert to interpret the results. Also, since it is a panel test, values are generally interpreted together and not seen as individual numbers.

    What Is A Thyroid

    Overactive Thyroid Symptoms

    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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    Thyroid Hormone Test Results

    Other medications can interfere with thyroid laboratory measurements, but not with the actual functioning of the thyroid.

    A few examples of these medications include:

    Lastly, research has found that the supplement biotin can interfere with the measurement of thyroid blood tests. Therefore, it’s recommended that people who take biotin stop doing so two days prior to having their thyroid blood tests.

    Should I Fast For A Thyroid Test

    Do I have to fast for TSH blood work? Do thyroid blood tests require fasting?

    In terms of fasting, most doctors tell thyroid patients that its not necessary to fast before a blood test. However, researchers have found that after eating, our TSH level becomes suppressed.

    This means that a high TSH could instead look much lower after eating, and borderline levels no longer borderline. As so many doctors use the TSH level to decide if a patient is adequately treated, or in need of more or less thyroid medication, this could result in patients having their thyroid medication wrongly altered, or even being told that their borderline hypothyroidism is now normal, resulting in some thyroid patients being inadequately treated for their thyroid condition. All because they ate before their test.

    Therefore, your TSH level is likely to be at its highest and most reflective of its underlying status, when tested after fasting, in the early morning.

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    What Should Be Tested For

    Some doctors test only TSH and measure thyroid function from that alone. But TSH may not show the entire scenario. Its best to test free T3 and free T4 too.

    A thyroid panel can be ordered for by your doctor. The thyroid panel consists of TSH, total T4, T3 uptake, and calculated T7 index. TSH is a good start while total T4 is helpful. T3 uptake is related to thyroxine-binding hormones and not the T3 hormone. The above thyroid panel provides a lot of useful information for interpreting the TSH value.

    The tests done in the study did not contain levels T3 and T4. T4 is a more popular and cheaper test. When the levels of the free hormone in the blood are measured, the doctor wants to know how much free hormone is available to work on the cellular level.

    The total hormone levels combine bound levels and free levels. Most hormones are bound by protein to carry them all around the bloodstream so that they be made available at faraway sites. Once the free hormone is used by a cell, the binding protein releases another hormone, so the hormone is made available. Hormone binding is a complex process that is usually affected by other circulating hormones.

    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.

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    What Are Thyroid Hormone Blood Tests

    The thyroid is a butterfly-shaped gland located near your Adamâs apple that produces the hormones triiodothyronine and thyroxine .4 T3 and T4 regulate all aspects of your metabolism, such as the rate at which your body uses carbohydrates, your body temperature, and your protein production.3

    When your thyroid does not produce enough of these hormones , you may experience a lack of energy, weight gain, and depression. 2 Thyroid function blood testsâalso known as thyroid hormone blood testsâcan determine whether your thyroid is functioning correctly.7 A healthcare provider can administer these tests to help determine whatâs causing your symptoms and which treatment may work best for you.

    How Should I Prepare For A Thyroid Function Test

    For the most part, you do not need to do anything before having this test. However, some medicines may change the result of the thyroid function test.

    • Tell your doctor about all prescription and non-prescription medication you take.
    • If you are taking thyroid medicines, tell your doctor when you took your last dose. Your doctor may ask that you stop taking thyroid medicines temporarily before having this test.

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    Fasting And Thyroid Conditions: Decrease Inflammation

    Fasting is the quickest way to decrease cellular inflammation, because it allows the body to direct all of its energy towards healing. I say this with confidence because it has changed my life and made a greater impact on improving my cellular health than any other strategy.

    In onestudy conducted on laboratory mice, researchers note that nuclear T3 levels are maintained at relatively normal levels in the pituitary of the fasted animal and fractional T3 receptor occupancy may actually increase.4

    Anotherstudy comparing the levels of thyroid levels between impaired fasting glucose and impaired glucose tolerance found that fasting subjects had higher levels of F3, while those who were glucose impaired had lower levels of F3. Researchers concluded that the difference in thyroid hormone levels may play an important role in the different pathological mechanisms of IFG and IGT.5

    As a person gets accustomed to fasting, the body gets more and more efficient with every subsequent fast. Fasting on a consistent basis can help reduce or even eliminate many of the ailments in todays society: cells become more efficient at utilizing fat, which burns cleaner than glucose. The body becomes more responsive to hormones. Brain fog dissipates, weight loss is easier, and most hormonal problems may be eliminated, and that includes thyroid conditions.


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