Why Thyroid Blood Tests Aren’t Always Accurate.

Updated January 2022

Blood tests for thyroid function measure the amount of TSH, T4, and T3 in the bloodstream. But thyroid hormones don’t operate within the bloodstream; the action takes place in the cells themselves. Blood tests are measuring how much thyroid hormone is  swimming around in the blood stream, but not what is in the cell.

Traditional medical professionals know that thyroid blood tests are less than perfect.

The Journal of Clinical Psychiatry has reported: Laboratory blood tests for thyroid may be inaccurate for many who get tested for hypothyroid disorder.

Compounding the problem of using standard blood tests to diagnose hypothyroid is the inability of doctors to agree on the laboratory parameters. According to the American Association of Clinical Endocrinologists (AACE) guidelines, doctors have typically been basing their diagnoses on the “normal” range for the TSH test. The typical normal TSH levels at most laboratories, has fallen between the 0.5 to 5.0 range. Those with a TSH below .5 are considered to have too much thyroid hormone (hyperthyroid). Those whose test results are above 5 are considered to have too little thyroid (hypothyroid). However, it’s not uncommon to find doctors, including endocrinologists (thyroid specialist), who withhold the diagnosis and treatment of hypothyroid until a patient’s TSH tests read considerably above 10. Other doctors believe that anyone who has a TSH above 2 and complains of hypothyroid symptoms (depression, fatigue, brain fog, etc.) should be placed on thyroid hormone. While doctors debate which parameters or numbers are correct, millions of low thyroid patients are not properly diagnosed and treated.

Patients often relate that they, and sometimes their doctors, suspect a thyroid problem only to have their blood work return normal.

Doctors are typically reluctant to prescribe thyroid replacement therapy without a definitive test that reveals true hypothyroid. They’re afraid that by doing so, they would jeopardize the health of the patient. And true, excess thyroid can cause several unwanted health problems, including elevated heart rate, rapid pulse, and accelerated bone loss.

However, millions suffer with symptoms far worse than these when prescription therapy is withheld. Certainly the dangers of thyroid replacement therapy should be a concern. But, if you weigh the pros and cons of administering thyroid replacement therapy to a patient with normal blood tests, yet all the symptoms of hypothyroid, fatigue, anxiety, depression, achy diffuse pain, weight gain, etc., it’s easy to see that withholding therapy should be considered malpractice. This is especially true in light of the fact that many of these patients are taking numerous, potential dangerous drugs, to cover-up the symptoms of hypothyroid; Provigil or Aderall to increase energy, antibiotics for chronic sinus infections, a laxative for constipation, NSAIDs for  pain, SSRI medication for depression, Neurontin for tingling in the hands and feet, and perhaps a benzodiazepine  like Ativan or Xanax for anxiety.

All of these drugs may cause side effects that may cause further symptoms (poor sleep, fatigue, depression, etc.). It’s not uncommon for my patients to be able to drastically reduce or eventually wean off these very medications once their thyroid disorder is corrected.

Mark Harmon, M.D.,  director of Cleveland Clinic’s Center for Functional Medicine, and the Founder of The Ultra Wellness Center, and a ten-time #1 New York Times Bestselling author has this to say about thyroid testing –

“Most doctors just check something called thyroid-stimulating hormone (TSH), which doesn’t give a full picture of the thyroid. In fact, even the interpretation of this test is incorrect most of the time.

The newer guidelines of the American College of Endocrinology consider anybody with a TSH level over 3.0 as hypothyroid. (1) Most doctors think that only anything over 5 or 10 is worth treating. Unfortunately, this leaves millions suffering unnecessarily.”

Doctors typically diagnose thyroid problems by testing your TSH levels and sometimes your free T4 level. But some doctors and clinicians have brought the “normal” levels of those tests into question.

The diagnosis of “subclinical” hypothyroidism depends on having a TSH level higher than 5 m IU/ml and lower than 10 m IU/ml. As I mentioned above, new guidelines suggest anything over 3 is abnormal. While an improvement, practitioners following these guidelines may still miss many people who have normal test results and a malfunctioning thyroid system.

I recommend getting a complete thyroid panel including:

  • Thyroid-stimulating hormone (TSH), the ideal range is between 1 and 2 m IU/ ml
  • Free T4 and free T3 (the inactive and the active hormone)
  • Thyroid antibodies (TPO) and TGb looking for an autoimmune reaction that commonly goes undiagnosed if the other tests are normal, as doctors don’t routinely check this
  • If taking prescription thyroid medication get a Reverse T3. This test will show if your thyroid drug (usually synthetic thyroid T4 like Synthroid or Levothyroxine) is  properly converting to the active thyroid T3 hormone

Another option is Self Testing:

How To Self-Test For Low Thyroid

The test for low thyroid function according to Dr. Barnes protocol: First thing in the morning while still in bed, shake down and place a mercury thermometer (digital thermometers are not as accurate) under your arm and leave there for ten minutes.

Record your temperature in a daily log. Women who are still having menstrual cycles should take their temperature after the second and third days of the period. Menopausal women can take their temperature on any day.

If using a digital thermometer wait 2 hours after waking up and take Your temperature under the tongue (don’t eat, drink or brush your teeth 10 minutes before taking your temperature).

A reading at or below 97.8 strongly suggests hypothyroid. A reading above 98.6 may indicate hyperthyroidism (over active thyroid).

My patients with low body temperature or low thyroid function use an over the counter supplement Thyroid 200 to help boost their thyroid function.

SAVE 15% with the code:   THY200  (use the code, or click this link, to have the discount code automatically applied to your cart at checkout)

Did you get your free Thyroid report?

If not here it is once again:

These patients and hundreds of others who’ve worked personally with me have in fact beaten their fibromyalgia. You can read or listen to their stories by clicking the link below:


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2 replies
  1. Diana Creak
    Diana Creak says:

    All these fact sound so much like what I’m going through …. I’ve always read that there’s another test for thyroid but the doctors over rule it ?? Am I able to demand this test please x


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