Testing Your Thyroid: The Definitive Guide to Thyroid Lab Tests and Optimal Ranges

Thyroid disease affects hundreds of millions of people worldwide. Most who have it remain undiagnosed, and most who are diagnosed still struggle with thyroid-related symptoms like fatigue, weight gain, hair loss, and more.

Do you have thyroid disease? Are you on the proper thyroid treatment?

Thyroid labs are the only way to answer these questions.

Yet people can be helped only if the proper tests are ordered and correctly interpreted.

In nearly all cases, doctors fail to order the range of necessary tests or fail to interpret them in the most accurate ways. These problems occur commonly in both conventional and functional medicine.

Some doctors say they treat patients, not test results. They prefer not to test or to rely too much on lab results. They prefer to adjust medication based on symptoms.

Here is the thing – symptoms matter. There is a noble sentiment behind that, but it is misguided. If a doctor wishes to provide safe and lasting benefits to symptoms, they must know what is causing the symptoms and how well treatment works.

If one suspects thyroid issues, the first step is to test.

This blog will help you know which thyroid labs are most vital for you, what those labs mean, and what your results should be.

Being educated about your health and involved in medical decision-making is essential. Yet it is still critical to work with a doctor who you trust.

The perennial question is

           “What thyroid tests should I ask my doctor to test?”

The problem with this question is that it fails to consider the next step. If you don’t trust your doctor to know what tests to order, how can you assume they will know what to do with the results?

Educate yourself and be involved, but know you are part of a team.
With that perspective, here is the story about thyroid lab tests.

Thyroid 101

Every part of your body must work harmoniously for you to feel your best. Would you believe that at any given moment, your health is the function of over 9000 chemical reactions?

Imagine cogs turning within cogs within cogs – as in 9000 of them!
Your body’s hormones govern all of these chemical reactions. Your hormones are covered by tiny glands in your brain called the hypothalamus and pituitary gland.

Image Courtesy of By OpenStax & Tomáš Kebert & umimeto.org – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=95250832

Any part of the endocrine system can go wrong, but thyroid diseases are among the most common¹.

• Thyroid disease is one of the top reasons for prescription medication worldwide
• Thyroid disease is the single most common autoimmune disease
• Thyroid cancer is the world’s fastest-increasing type of cancer.

Your thyroid regulates:

• Your rate of metabolism. Think about energy levels and how easy or hard it is to maintain body weight.
• How your tissues repair themselves. This relates to hair loss, skin health, and muscle or tendon issues.
• The rate of nerve conduction. Here, we connect thyroid function to mood, mental sharpness, and coordination. Since nerves control your intestinal tract, your thyroid can also be related to intestinal issues.
• The activity of other hormones. Thyroid hormones are unique among hormones in that all cells have receptors for thyroid hormones. That means other hormones can’t work correctly if thyroid hormones are not in perfect balance. This consideration brings in issues of fertility, perimenopause, and difficult cycles.

Your thyroid is a butterfly-shaped gland in the back of your throat. On a fundamental level, it makes hormones that govern metabolism.

Role of Iodine

Your thyroid makes hormones using the mineral iodine. Iodine enters the bloodstream from the diet, personal care products, and supplements.
Once in the blood, the thyroid can pump iodine into itself. It uses iodine to make hormones. The hormones (T3, T4) are named for how many iodine atoms each contains.

These hormones leave the thyroid, circulate, and enter individual cells. Once there, they shed iodine atoms to change forms and activate the genes and mitochondria.

After the cells use them, they are released back into circulation. Some are broken down by the liver and kidneys and eliminated. Others are stored in carrier proteins for later use. Some are even stored in the intestinal tract.

In short, dozens of systems manage and rearrange thyroid hormones. Every cell of your body, and even different parts of the cell, uses thyroid hormones differently.

The concentration of thyroid hormones in the blood is microscopic. Have you ever seen an Olympic pool? Imagine if you poured a teaspoon of vanilla extract in one. That’s about how dilute thyroid hormones are in your bloodstream.

Yet it could be fatal if that amount was reduced to the equivalent of 1/4 of a teaspoon or raised to a tablespoon.

Thyroid Diseases

Given how powerful and closely regulated thyroid hormones are, it is no surprise that there is a chance for things to go wrong.

Thyroid disease occurs in three categories:

• Inflammatory
• Functional
• Structural

You’ll see that these categories often overlap, but here is how they are distinct.

Inflammatory

In the case of inflammatory disease, the immune system attacks the thyroid. This can damage the structure of the thyroid and cause it to function abnormally.

The most common examples are Hashimoto’s Thyroiditis, which is associated with a lack of thyroid hormone (hypothyroidism), and Graves’ disease, which is associated with too much thyroid hormone (hyperthyroidism).

Functional

In the case of functional disease, the thyroid makes the wrong amount of hormone. Hypothyroidism (too little) is the most common, but hyperthyroidism (too much) is also possible.

These conditions also occur if someone relies on thyroid medication and the dose is not correct for their current needs.

• Hypothyroidism (Hashimoto’s Disease) – an underactive thyroid gland
• Hyperthyroidism (Grave’s Disease) – an overactive thyroid gland

Structural Disease

Finally, we have structural disease. This is where the gland is not growing correctly. It is too large, too small, or has unhealthy tissue.

The most common example of this would be thyroid nodules. Other structural issues range from thyroid cancer to goiter to tissue shrinkage.

Thyroid Tests

Why is testing important?

There are four reasons to test your thyroid.

• Testing For Diagnosis – This is done if you don’t feel well and wonder if your thyroid is the culprit.
• Testing for Dosage – Is your medication working well, the right type, and how can we best explain your symptoms?
• Tracking autoimmunity – Some have risks and symptoms from the autoimmune side of thyroid disease. In those cases, it is essential to monitor antibody levels regardless of how the thyroid is working.
• Testing for health – Keeping your thyroid levels healthy is essential even if you are feeling fine. Just like blood sugar, blood cholesterol, or blood pressure, thyroid levels have predictive value on long-term health outcomes.

Each of these reasons correlates with different tests and different testing frequencies. Don’t think you need to do every thyroid test possible every time your blood is taken. Yet it is also important not to miss the important tests.

Types of Thyroid Tests

We can categorize thyroid tests into these same groups:

• Functional
• Inflammatory
• Structural

Functional and Inflammatory tests are both done almost exclusively with blood tests.

These are the tests most people refer to as thyroid tests. They are the most common and will be the ones we start with.

Please read about structural tests as well. They are not usually helpful in diagnosing symptoms but essential for preventing long-term risks.

Functional Tests

TSH

The first test to start with is the TSH.

TSH = Thyroid Stimulating Hormone. This is a hormone from the pituitary gland ‘telling’ the thyroid to work.

You may also see it written as hs-TSH. This means ‘highly sensitive’ and allows precise readings when the TSH is well below range. Most TSH assays today are highly sensitive, even if not labeled as such.

Opposite Day

The single most important thing to know is that the TSH is backward. A HIGH TSH means an UNDERactive thyroid. A LOW TSH means an OVERactive thyroid.

This is the test that is going to be used in almost all circumstances. It is the earliest sign that thyroid levels are changing.

According to most labs, the normal range is 0.4 – 4.5². If the thyroid shuts down, the TSH can get very high, as in 50, 200, or 300.

If the thyroid is overactive, or one is taking too much thyroid medication, the TSH goes below range. TSH does not go into negative numbers. The lowest possible reading is less than (<) 0.001.

T3 and T4

These are the two main hormones the thyroid gland releases into circulation.

T = Thyroglobulin. It is the backbone from which thyroid hormones are made.

3 and 4 = the number of iodine atoms.

T4 and T3 are among dozens of thyronamines (thyroid hormone proteins). They differ in how many iodine atoms they have and where they are attached to the molecule.

Thyroid hormones stimulate gene expression, protein synthesis, and mitochondrial activity. Together, those three cover all the activities fundamental to each of your body’s cells.

T4 is called a prohormone. This means it primarily allows your body to make it into T3 as needed.

But this is not its only role. We now know that T4 has some crucial jobs only it can do. Two examples are in the brain and a developing fetus. T4 gets into the brain more efficiently than T3, and T4 is the only one that can enter the baby across the placenta.

The relevance is that T4 is essential for those on thyroid medication. Some do well with a little T3 in addition to T4, but T4 is essential.

The thyroid secretes mainly (80-95%) T4 but some T3. After the hormone is secreted, most (60-80%) T4 is made into reverse T3; the remainder is made into T3, as in the image below.

Note that T3 and reverse T3 (rT3) have three iodine atoms. The only difference is where they are located.

T3 and T4 can be measured in two different ways:

• Free Hormones
• Total Hormones

Which is best? It depends.

Free hormones give us a better idea of our bloodstream’s active (and active) hormones.

Measuring T4 and T3 tells us:

• How much is being released
• How much is circulating
• How much is being converted (T4 to T3)

T4 – Free T4

T4 can be measured as total T4 or free T4. Total T4 is called ‘Total T4’ or just ‘T4. Free T4 may be abbreviated as fT4.

In the case of T4, free T4 is more accurate.

There is broad consensus that free T4 is preferred for three reasons:

1. It is the active fraction
2. It can be accurately measured
3. Variation between free T4 and total T4 is common

T3 – Total T3

Similarly, T3 can be ordered as Total T3 (T3) or free T3 (fT3).

In the case of T3, Total T3 is preferred. This is a subtle distinction. I used free T3 for many years, but I changed as the data became clearer. If technology advances, there might be a case to be made for free T3 in the future.

Here is why T3 is different.

1. Variations between total T3 and free T3 are rare, unlike with T4.
2. Most significantly, Free T3 is measured in such minuscule quantities that it is hard to measure accurately.

Since the amounts are so minuscule, variations in technology give inconsistent results. Therefore, total t3 is preferred. This is called Total T3, or just ‘T3’ on a lab order.

Reverse T3

Reverse T3 (rT3) is only measurable in one form. There is no free reverse T3.

RT3 is a hormone that is unfairly villainized. Sometimes, people who are unhealthy or overmedicated don’t feel well and have high levels of rT3. But the unhealthy or overmedicated part is to blame. rT3 is a safety valve, not the culprit.

I’ll talk a bit more about it in the normal vs optimal section. If you’d like to get a Ph.D. in rT3, here is a blog with as much as you’d like to know!

Inflammatory Tests

Thyroid Antibodies

There are four types of thyroid antibodies:

• Anti-thyroglobulin (anti-Tg) – is an attack on thyroglobulin, a common aspect of Hashimoto’s disease. It is the protein that stores iodine and forms the backbone of thyroid hormones. Anti-Tg is present in the majority of cases of Hashimoto’s in the years before the illness becomes apparent.
• Anti-thyroperoxidase (anti-TPO) – an enzyme involved with hormone production. It activates inactive iodide into active iodine to bind to thyroglobulin. Anti-TPO is present in the majority of cases of Hashimoto’s when the illness is active.
• Thyrotropin Receptor Antibodies (TRAbs) – These antibodies attack the TSH receptor. They can have activating effects, which may trigger the thyroid to release more hormone than the body wants, or have inhibiting effects, causing it to shut down.
• Thyroid Stimulating Immunoglobulin (TSI) is the primary type of TRAb in Graves disease. It stimulates the thyroid and raises the risk of Thyroid Eye Disease.

Thyroglobulin

Thyroglobulin is the protein that your thyroid uses to make hormones. It is a normal constituent of thyroid cells. Note that Thyroglobulin is not the same as anti-thyroglobulin. The latter is an antibody that attacks the thyroglobulin protein. The former is the protein itself.

As thyroid cells wear out and die, thyroglobulin is spilled into the bloodstream. Some cells wear out naturally – it is expected to have some thyroglobulin in the blood.

But when thyroglobulin is elevated, the thyroid is large, growing rapidly, or thyroid-like tissue, as in thyroid cancer, is increasing rapidly.

Less Common Tests

Other thyroid tests that are not regularly used are available. Some are useless due to technological advances, others are only needed in less typical cases, and others are unavailable through all medical laboratories.

Here are a few of the tests that fall into these categories.

• Thyroid Binding Globulin (TBG)
• TBII – Thyroid Binding Inhibitory Immunoglobulin
• TRH – Thyrotropin Releasing Hormone
• T3 RIA
• T3 Uptake
• T7 (T4 times T3 uptake)

Structural Evaluations

It is also essential to monitor the structure of your thyroid – how large it is, whether its components are as they should be, and whether its size is changing. It is best to track the structure of your thyroid in all three ways.

• Monthly Self-Exams – Drink some water, look in the mirror, and learn to feel the structure of your thyroid. Know what’s normal and when something feels wrong. Once you know how your thyroid should feel, you’ll be the first to know if something changes.
• Annual Doctor’s Exam – A good part of a yearly physical. You should expect your primary care doctor to do a thyroid exam just as they check your ears, throat, and lymph nodes. If they do not, you can request it.
• Ultrasound – Please get an ultrasound. It is essential, mainly because of the high risk of thyroid cancer in those with thyroid disease³. If you have thyroid disease – ask your primary care doctor or endocrinologist to order a baseline ultrasound. The baseline test results determine how often a repeat ultrasound will be appropriate for you and whether additional tests are needed.

Discovering Comorbidities

At the first stage of diagnosis, it is essential to understand what else might be wrong. Thyroid disease almost always occurs in the presence of other diseases called comorbidities.

These comorbidities may cause symptoms and risks regardless of your thyroid function. It has long been recognized that many people don’t feel better despite thyroid treatment. One of the top reasons is that they have undiagnosed comorbidities preventing them from feeling well.

By testing comorbidities, you can understand what steps will help your immune system and give you the best chance of reversing thyroid disease.
Here are a few of the top comorbidities to consider:

• Adrenal dysfunction (daily circadian rhythm)
• Anemias
• Atrophic gastritis
• Celiac disease
• Diabetes and blood sugar problems
• Fatty Liver disease
• Overweight and obesity
• Parathyroid disease

What Your Results Mean: Normal and Optimal Levels

Single test?

When considering the results of your tests, the first thing I’d like you to know is that any one result can be a fluke.

There are many reasons why you can have a set of thyroid results that show up once but are different on a retest, even if the retest is only a few days later.

Never base a diagnosis or treatment on a single result. Over 30% of the time, someone with abnormal thyroid levels has perfectly normal results if they do nothing more than retest in a few weeks.

Get Help

Now that you have results, what do they mean? This blog will talk about each test and its normal and optimal ranges. Yet lab tests can only be intercepted in the context of your:

• Other lab tests
• Symptoms
• Health history
• Demographics
• Family history
• And more

You want guidance.

You can plug them into the Thyroid Lab Analyzer for automated help or consult with me in person for one-on-one guidance.

Normal vs. Optimal

I’ll talk about normal and optimal levels for each of these labs.

Normal levels are those printed on your lab report. They can vary from lab to lab, but these are generally average. Sometimes, average levels are not the best, especially for specific individuals.

Many health experts share lists of ‘optimal’ thyroid levels. I’m no exception, but I’d like you to take them all with a grain of salt.

• For most thyroid tests, it is never OK if the results are not normal
• You may be perfectly healthy with levels that are not optimal
• Optimal is not the same for all people

The valuable part of normal vs optimal is that some people needing thyroid medication feel better at some parts of the normal range than others. That’s OK.

Where optimal levels are misused is when:

1. People are put on medication because their levels are not optimal
2. People are given an overdose of medication, which pushes their TSH below range to make T3 ‘optimal’

With that said, let’s talk about the individual thyroid levels.

TSH

Normal

Most labs say the TSH is normal, between 0.4 and 4.5.

Optimal?

Some who need medication feel better when their TSH is low normal – as in 0.5 – 2.0. That’s OK.

Some people have hypothyroid symptoms when their TSH is above 2.0. That is real, but thyroid medications are not the answer.

Subclinical Hypothyroidism

If the TSH is elevated, but the T4 is still present, this is called subclinical hypothyroidism. It can cause hypothyroid symptoms, but medications rarely provide more benefit than risk. The Thyroid Reset Diet has been clinically proven to help the majority of people reverse suboptimal and subclinical hypothyroidism.

Overt Hypothyroidism

If the TSH is significantly elevated, as in 20-300, and the TT4 is well below range, the condition is usually overt hypothyroidism. This is true hypothyroidism. There is too little thyroid hormone. Medication is helpful and appropriate. Yet, some can still respond to dietary change without it.

If the TSH is below range, this is called hyperthyroidism. The most common reasons are too much thyroid medication or undiagnosed Graves’ disease.

There are risks for hyperthyroidism, such as:

• Brain damage
• Bone loss
• Heart disease

These risks are real even if T3 and T4 are not elevated.

Free Hormones (Free T4 and Total T3 Tests)

These both have a wide range of normal and many different units reported.

In general, things are acceptable if they are in range. Healthier populations tend to have them both mid-range or low normal.

Some health experts argue the opposite. They assume that since some people feel better with a low-normal TSH, they must have a high-normal T3. Given how much regulation T3 has, the one does not follow the other.

Human studies show that consistently high levels of T3 are a known risk for breast cancer and diabetes.

Furthermore, if one tries to use medication to raise T3 and/or T4 to high-normal – it pushes the TSH below range. This creates risks because TSH is needed to repair bones and blood vessels normally.

Thyroid Antibodies

Immune tests like thyroid antibodies are trickier. The same antibodies at the same level do not always act in the same way.

• Some people with Hashimoto’s never have measurable antibodies⁴
• Some with high antibodies never get Hashimoto’s
• Antibodies can fluctuate significantly from one test to the next

What can we say?

Anti-thyroglobulin is not as commonly high, but when it is, it is usually a cause of symptoms.

Anti-thyroid peroxidase is almost always a big deal in the 1000s.

Action steps for interpreting antibodies:

1. Get help
2. Don’t put too much weight on one reading
3. If they are extremely high, consider nutraceuticals. Antibody Support has been clinically proven to help

Reverse T3

I don’t routinely test rT3. Many perfectly healthy people have high or low levels of rT3. This is of no known significance.

Many people with thyroid problems have normal rT3.

If you have thyroid issues and elevated rT3, it can mean:

• Nothing – some labs have unusual ranges
• Overmedicated – your body will make more rT3 if your medication dose is too high
• Comorbidity – if your health is compromised in some way, your body may deactivate more thyroid hormone to slow your metabolism. The answer is not hacking rT3; it is fixing the comorbidity.

Summary of Optimal Ranges

Action Steps for Thyroid Labs

When should you test?

This may be one of the most critical points of the article. Please read over these guidelines closely. I found that in many cases of fluctuating or erratic thyroid levels, the problem comes down to the patient needing to be told to test in a way that will yield consistent results.

1. Test in the morning. Your thyroid levels follow a circadian rhythm like cortisol or other hormones. 7-9 AM is best.
2. Test before consuming food, pills, or coffee. Only have water before your test. Thyroid levels change my fasting state to a non-fasted state.
3. Test before taking your thyroid medication. When you test after taking the pill, the levels of T3 and T4 can be highly erratic for the following one to 10 hours.
4. Do not test between days 10 through 20 of your menstrual cycle. Consider Day 1 as the first day of menstrual flow. Days 1-9 or 21-28 are best. If you are a man, a menopausal woman, or a woman with irregular menstrual cycles, this will not apply to you.
5. Skip all supplements for three days before your thyroid labs. Even appropriate supplements can cause your levels to be inconsistent.

What should I test?

Here are the tests that are needed for the different testing reasons:

• Diagnosis – if you’re unsure if your thyroid is a problem, a TSH and thyroid antibodies can be enough for a screen.
• Dosage – if you’re on medication, a TSH, free T4, and total T3 will give you a good sense of how it is working and whether you might need a different dose.
• Autoimmune Disease – if you have Hashimoto’s or Graves, it is also helpful to track thyroid antibodies.
• Thyroid Cancer – If you’ve had thyroid cancer, it is often helpful to test Thyroglobulin (not anti-thyroglobulin) along with other thyroid tests and thyroid structural tests when tracking for possible recurrence.
• General health – If you feel well and want to be sure thyroid issues are not creating any health risks, an annual TSH test is adequate. If it is abnormal, further testing would be appropriate.

How often should you test?

• If you’re trying to explain symptoms, check once.
• If you’re on medication it is best to test twice yearly. After adjusting a dose one can retest in 1 – 3 months. Once things have stabilized, then a 6-month schedule is adequate.
• For tracking antibodies, they can be checked every 3-6 months. Shorter timeframes may not show meaningful changes

Common Issues with Thyroid Testing

These are some of the common issues we might encounter when testing our thyroid gland:

• T3 Too High – If everything else is normal, this usually results from taking thyroid medication before your blood test rather than after.
• TSH Too Low is a risk factor, so it’s worth understanding. If you only feel well when your TSH is too low, some other hidden cause has not been identified.
• Erratic Antibody Levels – thyroid antibodies are suitable to confirm diagnoses, but they don’t rule it out when they are negative. They may be culprits behind infertility or anxiety⁵. Otherwise, changes in them are not likely to affect your health. They can go up and down randomly.
• TSH Drift – Your TSH takes about three months to level out after some thyroid treatment or lifestyle change. If you wish to see it lower and it moves down within less than three months, your efforts may be working. Give more time before taking further steps.

In most states, you can order your blood tests. It’s just like any other version of online shopping. Once you’re done, you’ll be given an order and a nearby location for a blood draw.

There are many options for online labs. I’ve chosen some of the most accurate and cost-effective options.

Here are my Recommended Tests.

In Closing

If your health is not good, check your thyroid. If your thyroid levels are not good, find out why.

Thyroid medications have their place, but after 30 years of practice, I find that they are needed by no more than 5-9% of those with thyroid disease.

The answer is mostly from diet, supplements, and managing comorbidities.

P.S. Whenever you are ready, here is how I can help you now:

1. Schedule a Thyroid Second Opinion with me, Dr. C, Click Here for Details
2. Need a Personalized Supplement? Check out My Thyroid Specific Formulations
3. Download and use my Favorite Recipes Cookbook Here
4. Check out my podcast Medical Myths, Legends, and Fairytales Here

Dr. Alan Glen Christianson (Dr. C) is a board-certified Naturopathic Endocrinologist, and the author of The NY Times bestselling Adrenal Reset Diet, Metabolism Reset Diet, Thyroid Reset Diet, and the Healing Hormone Cookbook.

Dr. C’s gift for figuring out what really works has helped hundreds of thousands of people reverse thyroid disease, lose weight, diabetes, and regain energy. Learn more about the surprising story that started his quest.