Best Lab Tests for Thyroid Problems — Bridgit Danner, Functional Health Coach & Detox Expert

TSH (Thyroid Stimulating Hormone): “The Trigger”

This is the ‘thyroid hormone’ that is most commonly tested in conventional medicine. TSH is actually not made by the thyroid, but by the pituitary gland to stimulate the thyroid gland. More TSH is released according to a feedback loop, measuring thyroid hormone levels in the body.

A high TSH blood test can indicate insufficient active thyroid hormones, but it’s not enough information to make a useful, functional diagnosis. A low number can indicate hyperthyroidism or thyroid replacement therapy.

You can have hypothyroidism with normal TSH, so keep reading to learn more!

Total T4 (Thyroxine): “The Main Dish”

T4 is the most plentiful product of thyroid hormone production at 80%- 90%. T4 is technically an inactive hormone or prohormone that will need to become biologically active in a later step. Later, 85% of T4 will be converted to T3 by enzymes in the deiodinase system in multiple locations, including the gut, liver, brain, skeletal muscle and thyroid gland. (5)

High levels can indicate hyperthyroidism. Lower levels can indicate hypothyroidism.

Total T3 (Triiodothyronine): “The Sidekick”

T3 is also produced by the thyroid gland per stimulation of TSH, but at much lower levels than T4. It is also created later in the bloodstream and organs by the removal of one iodine atom from the outer ring of T4. T3 is bound to a protein and cannot be used by your cells.

According to, “T3…is the last test to become abnormal. Patients can be severely hypothyroid with a high TSH and low FT4 or FTI, but have a normal T3.” (6)

High levels can indicate hyperthyroidism. Lower levels can indicate hypothyroidism or Low T3 syndrome. (7)

Free T4 (Free Thyroxine): “A More Accurate One”

As you learned earlier, T4 is the most abundant thyroid hormone, but it is mainly bound to a protein and ‘inactive’ as a hormone. About 1% of total T4 is free T4 and available for your cells to use. (8)

Again according to, “Free T4 [testing] avoids any change the proteins could have, giving us a more accurate value for the T4 level.” (9)

High levels can indicate hyperthyroidism. Low levels can indicate hypothyroidism.

Free T3 (Free Triiodothyronine): “The Important One”

Free T3 could be high, indicating hyperthyroidism, but more likely we find it too low. It is important to test all the thyroid markers along the chain of interactions, but I consider free T3 to be one of the most critical markers of thyroid health.

A robust amount of free T3 can keep you feeling lively and fit, whereas a free T3 at the low end of the range can leave you dragging with nagging symptoms like brain fog and inability to lose weight.

Both free T3 and free T4 can stimulate a cellular thyroid hormone receptor, but “affinity for T3 is approximately 10-fold greater than T4, mak[ing] T3 the most potent TH [thyroid hormone].” (10)

Reverse T3 (Reverse Triiodothyronine): “The Deactivated One”

Reverse T3 is formed by removal of an iodine atom in the inner ring of T4 by an enzyme. Reverse T3 (rT3) in an inactive hormone and a high result on your lab test can mean that the body is not converting enough T4 to active thyroid hormone.

High rT3 values are rare but can indicate a serious illness such as nonthyroidal illness syndrome (NTI). This marker is part of a complete functional thyroid panel but you are unlikely to see it out of range. (11)

Thyroid Antibodies: “The Revealing Ones!”

According to a review in ISRN Endocrinology, “AITDs (autoimmune thyroid diseases) broadly include Graves’ disease (GD) and Hashimoto’s thyroiditis (HT) which are the most common causes of thyroid gland dysfunctions and nonendemic goiter.” (12)

According to, “[Hashimoto’s thyroiditis] affects as many as 10 million people in the US alone, and approximately 10% of women over age 30 have Hashimoto’s thyroiditis.” (13)

Ten percent of adult women have Hashimoto’s?! It seems incredible, but I see so much in my own practice that I can believe it.

The reason for this surge of autoimmunity is complex and not fully understood. It’s thanks to a mix of stress, immune weakness, genetics, gut permeability, food quality and toxins in the environment. You are also more vulnerable to Hashimoto’s post-partum and as you move into menopause. For the purpose of this article on labs, we won’t open that can of worms too much! (14, 15, 16, 17)

The point here is that autoimmunity is the most common cause of thyroid conditions, so we’d better test for a Hashimoto’s disease diagnosis (which can officially only be made by a physician)!

The most common autoimmune thyroid disease is Hashimoto’s thyroiditis, so it’s what we most commonly test for. We’ll cover the two antibodies for the Hashimoto’s test first:

Thyroid Peroxidase Antibodies (TPOAb) – Thyroid peroxidase (TPO) is an enzyme normally found in the thyroid gland that plays an important role in the production of thyroid hormones. A TPOAb test detects antibodies against TPO in the blood. (18)

Thyroglobulin Antibodies (TgAb)– This antibody attacks a protein, thyroglobulin, needed for thyroid hormone production.

The other autoimmune condition associated with the thyroid is called Grave’s disease. Grave’s disease presents more symptoms of hyperthyroidism, such as rapid heartbeat, sweating, and rapid weight loss. It is possible, but uncommon, to have both Grave’s disease and Hashimoto’s. If you suspect you have Grave’s disease, ask your practitioner for the following hyperthyroidism test:

Thyroid Stimulating Hormone Receptor Antibodies (TRAb)- The antibody attacks the Thyroid Stimulating Hormone (TSH) receptors within the thyroid gland. The “TRAb overrides the normal regulation of the thyroid, causing an overproduction of thyroid hormones [hyperthyroidism].” (19)

Other Helpful Blood Tests

Getting your blood drawn is not the most fun thing to do, so while we are at it I like to add on a Complete Blood Count (CBC) and test for vitamin D. These are pretty affordable add-ons that can give us further information.

A CBC is a very usual screening with a lot of markers, so I’ll just cover a few highlights, along with information on vitamin D, below.

25-hydroxy vitamin D

A vitamin D deficiency can lead to immune dysregulation, autoimmunity, blood sugar dysregulation, anxiety and more. It’s important to know your personal vitamin D level, know the optimal level, and supplement and retest as needed. (20)

Fasting glucose and HA1C

These two markers of blood sugar are a great snapshot of your short and long-term blood sugar levels. As many people dealing with hypothyroidism are also dealing with brain fog, headaches or excess weight, we want to know if blood sugar is too high.

WBC (White Blood Cell Count)

As you may know, some gut infections are associated with Hashimoto’s thyroiditis. While a blood test won’t directly tell you if you have a gut infection, we can get a sense of how your immune system is faring if your WBC is too high or too low, and if certain cell type percentages are off.

Two known infections associated with Hashimoto’s are blastocystis hominis parasitic infection of the large intestine and H. pylori bacterial infection of the stomach. (21) Optional is further testing for gut infections through a stool test with us.

RBC (Red Blood Cell Count) & Ferretin

Red blood cells transport oxygen to your cells for energy and brain function, among other things. If you are anemic, you are can be chronically fatigued and breathless. 

Anemia can occur in older adults or hypothyroid individuals as stomach acid levels decrease and digestion and assimilation of nutrients are not as strong. 

The breakdown of your RBC values can let us know if you may have B12 deficiency or iron-deficient anemia.

Ferritin is a measure of stored iron. Too little can mean you’re low on iron, which may contribute to chronic fatigue. Too much may indicate inflammation, cell damage or liver disease. (22, 23, 24)

Why Testing with Your MD May Fall Short

I meet many, many clients who suspect a thyroid problem, but have had incomplete testing, or have had no one to help them interpret their results correctly. 

I used to own an integrative wellness center that accepted health insurance. There were many benefits to this system, but I’m also aware of some of the drawbacks of this system.

If your primary care practitioner is not versed in autoimmune disease and a functional medical approach to thyroid management, they may not be able to order a complete thyroid panel as outlined above. Much of their time and ability to bill insurance is dictated by insurance guidelines.

Even if your practitioner is open-minded to your request and orders tests for you, they may not be able to interpret it for you in the way you hoped for. 

How to Test Right and Restore Your Health

The good news is that nowadays, in most U.S. states you can order tests yourself online, which is awesome! The drawback to this system is that you may not know how to interpret the test, or the best, customized protocol to improve your health.

I’ve been wanting to address the problem of incomplete thyroid testing in our community for a while now, and am thrilled to say that we now have a solution for you!

Introducing our Thyroid+ Testing and Review! This combination of pre-paid local lab testing and a private online consultation with our team will:

This content was originally published here.

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