What is the best test for hypothyroidism?

What Is The Best Test For Hypothyroidism? Getting the Right Diagnosis for Your Symptoms

by Charlotte

When Mark first began feeling tired, he assumed that he was coming down with something. But as time wore on, he didn’t feel any better. Could it be stress? Not exercising enough? Not eating well? It seemed like there were endless possibilities to explain his fatigue. Yet even as he diligently tried new strategies for coping—sleeping better, exercising more, changing his diet—the feeling remained. It wasn’t until his practitioner mentioned hypothyroidism that he considered the possibility. All the pieces seemed to fit, and symptoms he had assumed were simply due to age or lifestyle were suddenly cast in a new light.

Hypothyroidism occurs when your body doesn’t have enough of the thyroid hormones it needs to maintain healthy function. This can be caused by problems with your thyroid gland itself, which secretes thyroid hormones that regulate your body’s metabolism and other functions, or problems with your pituitary gland, which secretes hormones that influence the thyroid. Many people only realize this is happening after they begin experiencing otherwise unexplained weight gain, fatigue, or difficulty concentrating.

However, not all people with hypothyroidism experience noticeable symptoms. While only 0.3% of people are thought to have symptomatic hypothyroidism, as many as 4.3% of people may have subclinical hypothyroidism. And a lack of overt symptoms doesn’t mean a lack of consequences. For example, even if your hypothyroidism is asymptomatic, it may still put you at a 19% higher risk of experiencing coronary heart disease in the long-term. This means that if you suspect that you’re experiencing or at risk for thyroid issues, you should get tested for hypothyroidism, if only to rule it out. But what is the best test for hypothyroidism? And what should you do if your practitioner says that your thyroid is fine, but you’re still experiencing symptoms?

Start With the TSH Test

The best initial test for hypothyroidism is the thyroid stimulating hormone (TSH) test, which is a blood test used to assess the level of thyroid stimulating hormone your body is releasing. Your body produces TSH via the pituitary gland and causes—or “stimulates”—your thyroid gland to secrete thyroid hormones like triiodothyronine (T3) and thyroxine (T4). The hormones produced by your thyroid itself subsequently regulate your body’s metabolism, heart rate, and breathing rate.

If your thyroid gland is not producing enough of its own hormones, the pituitary gland can attempt to stimulate it by releasing more TSH. As such, high TSH values are a strong indication of hypothyroidism. But problems with the pituitary gland itself can lead to low TSH, which will subsequently cause symptoms of hypothyroidism even if your thyroid itself is in good health. It is important to note, however, that low TSH typically indicates hyperthyroidism—or excessive thyroid hormone production—which means that it can sometimes be difficult to diagnose hypothyroidism with a single lab test. This is because the TSH test only measures TSH itself and does not give you any information about what your thyroid levels actually are.

Thyroid Hormone Testing Can Confirm a Hypothyroidism Diagnosis

In order to gain a more detailed understanding of your thyroid function, many practitioners will test your total T4 (TT4) or free T4 levels (fT4) at the same time that they test TSH to confirm or rule out hypothyroidism. In other cases, these tests will be recommended only if your TSH level is abnormal.

Of the two T4 tests, the fT4 is considered the most reliable. The “free” refers to the hormones which are circulating in your body rather than the hormones which are currently interacting with cells, which aren’t free for other cells to use at the same time. This gives your practitioner an idea of the levels of these hormones from a perspective of what your body can actually use instead of merely a statistic summarizing the total level of those hormones.

A T4 test in either form is essential because, unlike the TSH test, it measures hormones produced by the thyroid itself, allowing your practitioner to gain insight into the cause of abnormal TSH levels. A low T4 level suggests that your thyroid is underactive, resulting in hypothyroidism, while a high T4 level suggests hyperthyroidism. It’s also important to note that you can have high or low T4 levels even with normal TSH, which would be missed entirely if TSH is tested alone. In other cases, your T4 levels can indicate a fully functional thyroid and your abnormal TSH results could point to a pituitary gland problem. Making this distinction is essential for ensuring you get the care you need.

Depending on your symptoms, your practitioner may also recommend a free T3 test (fT3), as low T3 could also be an indicator of hypothyroidism. Because T4 is converted to T3, low T3 levels can indicate that this process is impaired. The most common reasons for low T4 to T3 conversion include stress and nutrient deficiencies such as selenium, zinc. and Vitamin A.

Recognizing Mild Hypothyroidism

If your test results show that your TSH levels are above a certain threshold, your practitioner will probably diagnose you with hypothyroidism and recommend that you begin treatment. But it’s important to remember that assessing hypothyroidism via TSH levels alone can be highly misleading and compromise outcomes. For example, if a patient’s TSH is near normal but they’re still experiencing symptoms, they may not do not get the care they need unless T4 or T3 tests are also performed. This is particularly true if your practitioner is using older guidelines for TSH that have different cutoff points for when patients should be treated than more current guidelines. If your practitioner says all your tests are normal or does not do thorough testing, you may need to look elsewhere to get help and find relief from your symptoms.

Getting the Right Treatment

If you are experiencing symptoms of hypothyroidism, you owe it to yourself to get thyroid function testing from a practitioner with expertise in hormone health. Many general practitioners still use outdated diagnostic guidelines, fail to appreciate the symptoms associated with mild hypothyroidism, or not be aware or know that the TSH test alone is insufficient for assessing thyroid health. It is thus worthwhile to seek out a practitioner who specializes in treating thyroid disorders and will work with you to assess the specific nature of your thyroid issues by using modern diagnostic tools.

A highly qualified practitioner will be able to provide significant diagnostic clarity and can identify hypothyroidism or conclude that you are experiencing a disorder with similar symptoms, even if it doesn’t involve your thyroid. This is essential because many illnesses and disorders feature symptoms like fatigue and poor concentration, and discriminating between pathologies and hypothyroidism can lead to a big improvement in your health. In some cases, it can even be life-saving.

If you are diagnosed with hypothyroidism, you shouldn’t worry about any extreme treatments or major lifestyle changes. Most likely, you will be prescribed a medication like levothyroxine or another form of hormone replacement therapy, which compensates for your underactive thyroid and addresses your symptoms. While you’ll need to take this medication every day, most people experience few side effects and find that the majority of their hypothyroidism symptoms are kept at bay with regular treatment.

Don’t let your apprehension about the different kinds of thyroid tests hold you back from seeking the testing and the therapy that your body may need. You owe it to yourself to seek out the most qualified practitioner, undergo the best tests for hypothyroidism, and explore any path to better health.

The BodyLogicMD network can ensure you get modern, reliable diagnostic testing and expert care from a highly-trained practitioner who specializes in hormone replacement therapy and integrative medicine. BodyLogicMD-affiliated practitioners are among the top medical professionals in the nation and specially certified to help you address thyroid disorders and other hormone conditions so that you can experience the life you deserve. Get started on a customized treatment plan designed to fit your lifestyle and help you reach optimal wellness— contact a local practitioner to schedule your first appointment or take the BodyLogicMD Hormonal Balance Quiz today.

Disclaimer: These statements have not been evaluated by the Food and Drug Administration. All content on this website is for informational purposes only. The content is not intended diagnose, treat, cure or prevent diseases.


  • Charlotte

    Charlotte is a patient care coordinator specializing in bioidentical hormone replacement therapy. She is committed to helping patients who struggle with the symptoms of hormonal change and imbalance explore their treatment options and develop effective strategies to optimize wellness.