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Understanding Thyroid Tests

A blood test is the best way to monitor thyroid health. Do you need one?

Medically reviewed by

Jillian LoPiano, M.D.


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Key takeaways
  • Your thyroid regulates your body’s metabolism, directly impacting energy levels.
  • Signs of thyroid disease can be easy to miss.
  • Testing thyroid-stimulating hormone levels in the blood is a first step in screening for thyroid problems.
  • People with autoimmune conditions or a family history of thyroid disease should have their thyroid hormone levels checked regularly.

Located just under the voice box at the front of the neck, your thyroid gland has the enormous task of regulating body metabolism, growth and development.¹ 

Working on demand, a healthy thyroid will release just the right amount of thyroid hormones into the bloodstream. If the body needs more energy — for instance, if you are cold or pregnant — the thyroid will produce more hormones. Once thyroid hormone levels are adequate for the body’s needs, the thyroid takes a break. 

With thyroid disease, however, this essential gland either produces too little hormone (hypothyroidism) or too much hormone (hyperthyroidism). Unfortunately, abnormal thyroid function can mimic many other medical conditions. A thyroid blood test is the only way to tell if your thyroid is functioning well. 

What do thyroid tests check for? 

Thyroid tests check for hypo- and hyperthyroidism.

Thyroid tests don’t diagnose other conditions like thyroid cancer, but a doctor might order one to see how cancer treatments are affecting thyroid function.

What are the main thyroid tests?

There is more than one blood test to check thyroid activity, and each one evaluates different patterns of thyroid function: 

TSH test

Thyroid-stimulating hormone, or TSH, controls overall thyroid function. That’s why a TSH test is typically the first — and often the only — thyroid health screen you’ll experience.² 

Elevated TSH levels may indicate an underactive thyroid, or hypothyroidism. Low TSH levels, on the other hand, may indicate an overactive thyroid, or hyperthyroidism.³ 

T4 tests

Thyroxine, also called T4 because it contains four iodine atoms, is the primary hormone secreted by the thyroid gland. 

The thyroid gland produces T4 hormones in response to TSH. When the pituitary gland senses there isn’t enough T4 in the bloodstream, it makes TSH to “turn on” the thyroid gland, encouraging the thyroid to produce more T4. On the other hand, if there is enough T4 in the bloodstream, the pituitary gland will pull back on TSH, which then slows T4 production. 

T4 tests measure thyroxine in the blood, indicating thyroid disease if there is too much (i.e., overactive, or hyperthyroid) or too little (i.e., underactive, or hypothyroid).

T4 has two different forms: 

  • Bound T4: This hormone is attached to proteins in the blood and does not enter body tissues.
  • Free T4: This hormone is available to enter body tissues and affects overall body functioning.

A total T4 test measures both bound and free T4 levels, while a free T4 test measures only free T4 hormone levels in the blood. 

Most healthcare professionals consider results from a free T4 test more accurate, especially when checked against a TSH test. 

T3 total test

An overactive thyroid usually comes with elevated levels of triiodothyronine, aka T3, named for its three iodine atoms. 

A T3 total test can be used to diagnose hyperthyroidism, even if T4 levels are normal, or to measure the severity of a hyperthyroid condition. T3 tests aren’t used to diagnose hypothyroidism. 

Thyroid antibodies test

A doctor or nurse practitioner may request a thyroid antibody test to rule out an autoimmune thyroid condition. In these cases, a person’s immune system begins attacking thyroid cell proteins by mistake, usually with thyroid peroxidase antibodies, thyroglobulin antibodies, or thyroid receptor antibodies.

A thyroid antibody test can help diagnose an autoimmune cause of thyroid disease but isn’t used to monitor conditions: for that, TSH and T4 tests are more common.

Common symptoms of thyroid disease

Body temperature can be a telltale sign of thyroid problems, especially if yours is different compared to others around you. You may be consistently too cold (possible hypothyroidism), or overheated and sweaty (possible hyperthyroidism). 

Common symptoms of an underactive thyroid, or hypothyroidism, include:¹⁰

  • Weight gain
  • Unexplained fatigue
  • Cold hands
  • Heavy and frequent menstrual periods
  • Infertility
  • Coarse or thinning hair
  • Dry or flaky skin conditions

With an overactive thyroid, or hyperthyroidism, you may experience:¹¹ 

  • Weight loss
  • Difficulty sleeping
  • Heart palpitations
  • Irregular or stopped menstrual periods
  • Muscle weakness
  • Increased sensitivity to heat
  • Excess sweating
  • Anxiety

When should I have my thyroid tested?

Because a thyroid issue can affect anyone at any time, the short answer is it’s never a bad time for a thyroid test if you’re experiencing symptoms of thyroid disease. 

Healthcare professionals also recommend testing if you: 

  • Have a family history: Thyroid dysfunction often runs in families. Anyone with known family members with the disease should be regularly screened.¹²
  • Have an autoimmune condition: People with autoimmune conditions such as type 1 diabetes, celiac disease, lupus and rheumatoid arthritis are also at increased risk of thyroid disease.
  • Are trying to get pregnant: Since thyroid conditions can affect your ability to conceive, screening is recommended if you’re trying for a baby.¹³
  • Are in the first trimester of pregnancy: Untreated hyperthyroidism and Graves’ disease can affect a developing pregnancy, so it’s important to screen during early pregnancy if you haven’t already.¹⁴

For most people, abnormal thyroid functioning can be hard to recognize because its symptoms, such as dry skin or weight gain, can be easily overlooked or explained by other things, such as stress.

Thyroid hormone production can also be affected by childbirth (a temporary condition called postpartum thyroiditis), low iodine levels, cancer, or swollen nodules in the neck that impact thyroid function.¹⁵ 

Can I test my thyroid at home?

You can easily check your TSH levels with an at-home test

With a quick blood sample sent away for analysis, lab test results will show if your TSH baseline levels are normal or abnormal, potentially signaling thyroid dysfunction. 

With these results in hand, you can follow up with your doctor, who may check your neck and thyroid area for any swelling, or may order more tests to check T3 and T4 levels and screen for thyroid antibodies. 

Understanding your test results

Your at-home test will clearly state whether your TSH levels fall outside normal ranges, indicating either an underactive or overactive thyroid gland. 

Normal levels of TSH for adults fall between 0.40 and 5 mU/L (milli-international units per liter of blood).

If your levels are borderline, you’re having symptoms, or carry risk factors for thyroid disease, follow up with your doctor. 

How accurate are at-home thyroid tests?

imaware’s at-home tests are analyzed and verified by healthcare professionals in an accredited lab setting. 

Our Thyroid Screening Tests don’t measure levels of thyroid hormones T3 and T4; rather they check TSH, a common and reliable way to screen for thyroid disease.¹⁶ 


Any treatment of thyroid disorders is about managing an imbalance and bringing thyroid hormone levels back into a normal range. 

Your healthcare provider will suggest different options depending on your thyroid condition: hypothyroidism is commonly managed with the drug levothyroxine, a synthetic thyroid hormone.

Managing hyperthyroidism depends on the severity and cause of the disease, and can include a variety of pharmaceutical or surgical treatments.


Managing a thyroid hormone imbalance starts with knowing you have one in the first place. 

Because the symptoms of abnormal thyroid activity are so varied and easily mistaken for other conditions, having your TSH levels checked is a good first step to ruling out a thyroid issue. If your levels are abnormal, or even borderline, it’s worth a follow-up with your healthcare professional for additional blood tests and a physical exam. Most thyroid disorders are easy to manage with medical help.

Updated on
April 13, 2022
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1. NCBI. How does the thyroid gland work. Accessed March 21, 2022.

2. NIH. Thyroid Tests. Accessed March 20, 2022.

3. American Thyroid Association. Thyroid Function Tests. Accessed March 20, 2022.

4. American Thyroid Association. Thyroid Function Tests. Accessed March 20, 2022.

5. Medline Plus. Thyroxine (T4) Test. Accessed March 20, 2022

6. Medline Plus. Thyroxine (T4) Test. Accessed March 20, 2022

7. NIH. Thyroid Tests. Accessed March 20, 2022.

8. American Thyroid Association. Thyroid Function Tests. Accessed March 20, 2022.

9. American Thyroid Association. Thyroid Function Tests. Accessed March 20, 2022.

10. Lancet. Hypothyroidism. Accessed March 24, 2022.

11. Lancet. Hyperthyroidism. Accessed March 24, 2022.

12. The Clinical Biochemist Reviews. Genetics of Thyroid Function and Disease. Accessed March 24, 2022.

13. British Thyroid Foundation. Pregnancy and fertility in thyroid disorders. Accessed April 1, 2022.

14. British Thyroid Foundation. Pregnancy and fertility in thyroid disorders. Accessed April 1, 2022.

15. British Thyroid Foundation. Your thyroid explained. Accessed March 20, 2022.

16. American Thyroid Association. Thyroid Function Tests. Accessed March 20, 2022.

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