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What Is The Blood Test For Thyroid

Why Do I Need A Tsh Test

TSH test explained | Thyroid stimulating hormone test | Thyroid function test | Blood TSH test

You may need a TSH test if you have symptoms of too much thyroid hormone in your blood , or too little thyroid hormone .

Symptoms of hyperthyroidism, also known as overactive thyroid, include:

Symptoms of hypothyroidism, also known as underactive thyroid, include:

  • Weight gain
  • Low tolerance for cold temperatures
  • Irregular menstrual periods
  • Constipation

Reason #: The Tsh Controversy

TSH alone is not enough to manage your thyroid condition. There is a big push in the thyroid advocacy world against the blindness of doctors of using TSH to treat thyroid patients.

There are a few reasons for that. Firstly, the range used by conventional doctors is 0.5 5.0 whereby functional and integrative practitioners would want to see a healthy person to have their TSH in the 1-2 range.

You see, I also had a perfect TSH of 1.6 to 1.8 even when my body was completely shutting down. This is due to reason #2, see below.

What Is A Thyroid Function Test

A thyroid function test is a blood test to check the levels of the hormones made by your thyroid gland. The test also checks the level of a hormone made by the pituitary gland in your brain, which acts on your thyroid gland.

The two hormones, thyroxine and thyroid-stimulating hormone , work together and are usually in balance. In a healthy person the brain produces just the right amount of TSH to keep the thyroid gland ticking over. The thyroid gland then produces just the right amount of thyroxine.

This is called a feedback loop: if the thyroid gland makes too much thyroxine it will feed back to the brain to make less TSH. This diagram shows the feedback loop between the thyroid gland in your neck and the pituitary gland in the brain:

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Can I Take The Test At Home

At-home thyroid test kits are commercially available without a prescription and measure the same hormones as the traditional thyroid panel.

For at-home testing, you prick your finger to get the necessary blood sample. That sample is then mailed to a laboratory that conducts the thyroid panel and makes the results available to you directly.

While at-home testing can measure thyroid levels, it is generally not a substitute for a test ordered by your doctor. If an at-home test detects abnormal thyroid levels, your doctor will likely recommend a new blood sample and thyroid panel to confirm the results. At-home tests for thyroid labs may not be as accurate as tests done in a laboratory.

How Do I Prepare For The Test

Thyroid Blood Testing

This blood test may be done any time during the day. Certain medicines can affect the results of your thyroid test. Ask your healthcare provider if you should wait to take your medicines until after your blood is taken. Wear a short-sleeved or loose shirt on the day of the test. This will make it easier to draw your blood.

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Thyroid Problems: What To Look For

It took me years to get properly diagnosed, and Im incredibly grateful that my children are healthy and my pregnancies were just fine. But, I also wish Id known the signs and what to ask the doctors to test.

Thyroid disease isnt something to mess around with, especially before and during pregnancy. Anyone who even suspects thyroid disease should get tested, preferably before pregnancy or as soon as possible. Ask to see the results and make sure the;doctor is using the most up-to-date references. Depending on the;doctors school of thought, they may be using outdated reference ranges.

Mildly Hypothyroid Subclinical Hypothyroid And Hypothyroid Whats The Difference

Theres a big difference between subclinical, mildly hypothyroid, and hypothyroid. These diagnoses determine the treatment options youll be offered.

Usually doctors wont prescribe thyroid therapy until a patient is clearly hypothyroid. Symptoms typically become stronger as hypothyroidism intensifies.

However, even mild hypothyroidism can be aggravating as TSH levels and symptoms increase. Talk to your doctor to determine your personal normal ranges and the best therapy to undertake. Logging your blood test results in the app might help you and your doctor when assessing your health.


1. Carvalho GA, et al. The clinical use of thyroid function tests, 2013

2. Wartofsky L, et al. The evidence for a narrower thyrotropin reference range is compelling, 2005

3. Hollowell JG, et al. Serum TSH, T, and thyroid antibodies in the United States population : National Health and Nutrition Examination Survey , 2002

4. Dunn JT. Guarding our nations thyroid health, 2002

5. Hubner U, et al. Continuous age-dependent reference ranges for thyroid hormones in neonates, infants, children and adolescents established using the ADVIA Centaur Analyzer, 2002

6. Surks MI, et al. Age-specific distribution of serum thyrotropin and antithyroid antibodies in the US population: implications for the prevalence of subclinical hypothyroidism, 2007

7. Kumar A, et al. Thyroid function tests in pregnancy, 2013

10. Lewandowsky K. Reference ranges for TSH and thyroid hormones, 2016

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What Blood Tests Do Doctors Use To Check Thyroid Function

Doctors may order one or more blood tests to check your thyroid function. Tests may include thyroid stimulating hormone , T4, T3, and thyroid antibody tests.

For these tests, a health care professional will draw blood from your arm and send it to a lab for testing. Your doctor will talk to you about your test results.

What About Thyroid Medications For Subclinical Hypothyroidism

What are your thyroid blood tests really saying?

Starting thyroid medication in subclinical hypothyroidism is considered controversial by endocrine groups. Exceptions are made for women who are contemplating pregnancy and for those who have overt hypothyroid symptoms. Guidelines clearly state that in order to avoid pregnancy complications and impaired development of offspring, women with subclinical hypothyroidism need to be treated with thyroid hormones.

At this stage, many patients may also opt to wait and see and may forgo thyroid medications in an effort to do it naturally. I know that I was one of those people, and I waited six months to get on medications after my diagnosis, but knowing what I know now, I am in favor of starting medications for subclinical hypothyroidism.


Korzeniowska and colleagues at the Medical University of Gdansk found that treating children with subclinical hypothyroidism with thyroid hormones, resulted in a decrease of inflammation. This means that the medications gave their thyroids a rest and resulted in a slowing down of the autoimmune attack, manifested by lower levels of thyroid antibodies.

Additionally, most patients with subclinical hypothyroidism feel so much better when they start on thyroid hormones.

I wanted to believe that these interventions were keeping me from getting worse until my husband and I took a red-eye flight from Los Angeles to visit friends on the East Coast in the winter. The lack of sleep combined with the cold weather put me in a hypothyroid flare.

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How Are The Samples Collected

The thyroid function test needs a blood sample collection. The blood sample is taken through venipuncture.

The skin area of the patient is disinfected using a suitable disinfectant.

1. Using a sterilized needle, blood is drawn from the vein.

2. Drawn blood is collected in the sterilized vial or test tube. Vials are preferred for blood sample collection.

The blood sample is further submitted to the pathology labs for thyroid test. The name, age of the patient, and the test name are recorded along with.;The thyroid test at home;is a convenient choice for patients, as it doesnt require any specific criteria. Most of the;pathology labs in India;offer the thyroid function test. Patients can also request for the;home sample collection.

What Are Thyroid Replacement Hormones And How Do They Work

Thyroid replacement hormones are medications used to treat hypothyroidism, a condition in which the production of thyroid hormone in the body is abnormally low. Thyroid hormones increase cellular metabolism that is responsible for growth, development of tissues, maintenance of brain function, body temperature regulation and several other cellular processes. Low levels of thyroid hormones in the body can result in many problems given the numerous activities that they mediate. The thyroid gland, a gland found in the lower neck is responsible for the production of thyroid hormones. It produces two main hormones, thyroxine and triiodothyronine . The hormone responsible for most of the biological effects in the body is T3. When T4 is released into the blood by the thyroid gland, most of it is converted to T3 which is responsible for the cellular metabolic processes. Commercially available thyroid hormones are either natural or synthetic . Desiccated thyroid or thyroid extract , a natural thyroid hormone is derived from beef or pork. Levothyroxine sodium , is the synthetic version of thyroxine ,liothyronine sodium , is the synthetic version of tT3 andliotrix is a synthetic thyroid hormone containing a mixture of T4and T3.

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Thyroid Disease + Pregnancy

Pregnancy can be such a wonderful and joyful time, even though it has its struggles.

But theres another side of pregnancy that can be heartbreaking and devastatingand that is infertility and loss. I recently shared a post about thyroid disease and the autoimmune condition often responsible for causing hypothyroidism, called Hashimotos thyroiditis. Not only can it cause debilitating fatigue, anxiety, hair loss, inability to lose weight, and so much more it can also cause infertility and problematic pregnancies.

This is something that the conventional medical community acknowledges, but there dont seem to be many good resources for pregnant women with thyroid disease. During pregnancy and postpartum, our hormones go through the ringer. This isnt a bad thing by any means, but because of the overwhelming amounts of hormonal changes, it can trigger an adverse thyroid reaction.

An undiagnosed or not properly managed thyroid problem can also lead to various complications with pregnancy and birth. In fact, untreated thyroid disease increases the chances of premature birth, preeclampsia, miscarriage, low birth weight, anemia, and even stillbirth.

When To Take Thyroid Medications To Get Accurate Lab Results

Hypothyroidism Undetected: Why It Is Often Missed
  • TSHâ This is a pituitary hormone that responds to low/high amounts of circulating thyroid hormone. In advanced cases of Hashimotoâs and primary hypothyroidism, this lab test will be elevated. In the case of Gravesâ disease the TSH will be low. People with Hashimotoâs 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. ;

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Thyroid Hormone Level Tests

There are four main thyroid hormones that have been identified: T1, T2, T3 and T4.

T4 and T3 are the two main thyroid hormones. T4 is known as prohormone and is 300 percent less biologically active than T3. T3 is the main biologically active thyroid hormone and gives us beautiful hair, replenishes our energy, and runs our metabolism.

You may have put together that most of the commonly prescribed thyroid medications like Synthroid and levothyroxine, only contain T4 , and thus they need to be converted to the active T3 form in the body.

On paper, the T4 to T3 conversion happens just fine, but in the real world, in real human bodies, we may not always convert T4 to T3.

We can reveal our T4 to T3 ratios and measure the hormone that is available to do its job in the body, by testing our free T4 and free T3 levels.

Free T3 and Free T4 tests measure the levels of active thyroid hormone circulating in the body.

Some clinicians may only test for T4, but T3 is also important to test, as some individuals may not be converting T4 to the active T3 properly. Thus, people may have a normal T4, but a low T3 level.

How Do You Know If You Are Converting Correctly?

Take a look at your free T3 and free T4 levels. Both should be in the optimal range. If the T4 is optimal, but the T3 is out of the optimal range, you know that your body is not making enough T3 hormone from the T4.

Optimal T4 reference range: 15-23 pmol/L

Optimal T3 reference range: 5-7 pmol/L

Thyroid Function Test Normal Values

Most common blood tests for thyroid are TSH, T4 and T3. Blood samples taken usually measures free or active T3 and T4. Thyroid test uses reference ranges to compare the results with the normal healthy population. Reference ranges for healthy thyroid are:

Test;;; ;; From ;To ;Units;

TSH;; ;;;; 0.4 ; ; ; ; ; ; 4.0mU/l

FT4 ; ; ; ; 9.0 ; ; ; ; ; ; 25.0pmol/l

FT3 ; ; ; ; 3.5 ; ; ; ; ; ; 7.8pmol/l

Blood Test To Manage Thyroid Disorder

The blood test for TSH is used to assure that ;your thyroid hormones level is satisfactory and under control. As increased levels of thyroid can adversely affect the cardio system in the long run so it must be under check before it is too late. In case of thyroid cancer efforts are made to keep the patients TSH level below the thyroid function test normal values .

In the initial stages of treatment, the blood tests for thyroid are referred every week as to keep a close check on the thyroid levels. In case of hypothyroidism a TSH test will be preferred whereas in;hyperthyroidism ;TSH test and T4 test are suggested. The frequency of test depends upon the severity aspect of the patient case history.

Measures before thyroid test?

Blood test for thyroid can be influenced either because of medications or illnesses. Thyroid function test normal values can be influenced widely due to some significant reasons:

When to have a thyroid test?

When A person is prone to thyroid?

How lifestyle affects thyroid ;

What are the Blood Tests for Thyroid? was last modified: February 10th, 2020 by Team Dr Lal PathLabs

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Are There Any Specific Tests For Hypothyroidism

Thyroxine is the primary hormone produced by the thyroid gland in response to stimulation by the pituitary gland.

A âfeedback systemâ exists between the thyroid gland and the pituitary gland. When T4 concentrations in the blood are low, the pituitary sends a signal to the thyroid gland using thyroid stimulating hormone , prompting the thyroid gland to produce more T4. When T4 levels in the circulation are adequate, the pituitary decreases its production of TSH, thereby reducing the production of T4.

âIf the total T4 concentration is well within the normal range, then your dog is not hypothyroid.â

Total T4 . ;T4 circulates in the blood in two forms; one form of the hormone is bound, or attached to proteins in the blood, while the other form circulates freely within the blood stream. Total T4 measures both forms of the hormone in a blood sample. If the total T4 concentration is well within the normal range, then your dog is not hypothyroid. If the total T4 concentration is at the low end or below the normal range, and your dog has supportive clinical signs, then hypothyroidism is likely. Unfortunately, there are conditions other than hypothyroidism that may cause the total T4 value to be reduced. These conditions include the presence of another illness or the administration of some drugs, such as anti-inflammatory medications. Your veterinarian may be able to measure total T4 levels in the veterinary office.

How Is It Used

What Thyroid Blood Test for Hypothyroidism?

Testing for thyroid antibodies, such as thyroid peroxidase antibody , is primarily ordered to help diagnose an autoimmune thyroid disease and to distinguish it from other forms of thyroid dysfunction.

One or more of the following tests may be performed to help establish a diagnosis of and/or monitor an autoimmune thyroid disorder:

  • Thyroid peroxidase antibody the most common test for autoimmune thyroid disease; it can be detected in Graves disease or Hashimoto thyroiditis.
  • Thyroglobulin antibody this antibody targets thyroglobulin, the storage form of thyroid hormones.
  • Thyroid stimulating hormone receptor antibodies includes two types of autoantibodies that attach to proteins in the thyroid to which TSH normally binds :
  • Thyroid stimulating immunoglobulin binds to receptors and promotes the production of thyroid hormones, leading to hyperthyroidism.
  • Thyroid binding inhibitory immunoglobulin blocks TSH from binding to receptors, blocking production of thyroid hormones and resulting in hypothyroidism.

TBII is not routinely tested, but TSI is often used to help diagnose Graves disease.

These tests may be ordered to help investigate the cause of an enlarged thyroid ;or other signs and symptoms associated with low or high thyroid hormone levels. Testing may be performed as a follow-up when other thyroid test results such as total or free T3, free T4, and/or TSH;indicate thyroid dysfunction.

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Thyroid Blood Test Normal Range

Total thyroxine

  • 0-5 days of age: 5.0-18.5 mcg/dL
  • 6 days-2 months: 5.4-17.0 mcg/dL
  • 3-11 months: 5.7-16.0 mcg/dL
  • 11-19 years: 5.9-13.2 mcg/dL

Adult : 4.5-11.7 mcg/dL

  • Values of more than 11.7 mcg/dL in adults or more than the age-related cutoffs in children are seen in hyperthyroidism and patients with acute thyroiditis.
  • Values below 4.5 mcg/dL in adults or below the age-related cutoffs in children are seen in hypothyroidism, myxedema, cretinism, chronic thyroiditis, and occasionally, subacute thyroiditis.
  • Increased total thyroxine is seen in pregnancy and patients who are on estrogen medication. These patients have increased total T4 levels .
  • A thyrotropin-releasing hormone stimulation test may be required for certain cases of hyperthyroidism.

Clinical findings are necessary to determine if thyroid-stimulating hormone, TBG, or free T4 testing is needed.

Free thyroxine

Adult : 80-200 ng/dL

Free triiodothyronine

  • Age > or =1 year: 2.8-4.4 pg/mL

Normally triiodothyronine circulates tightly bound to thyroxine-binding globulin and albumin. Only 0.3% of the total T3 is unbound ; the free fraction is the active form.

Thyroid stimulating hormone

Thyroid stimulating hormone normal levels:


  • 11-19 years: 0.5-4.3 mIU/L

Adults : 0.3-4.2 mIU/L

For diagnostic purposes, the results should always be assessed in conjunction with the patients medical history, clinical examination and other findings.


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