Episode - 4 Common Thyroid Blood Test Mistakes


4 Common Thyroid Blood Test Mistakes

While you’re on your thyroid healing journey, there are several blood markers you’ll need to monitor. Unfortunately, there are common mistakes that providers and patients make that can impact these tests, potentially producing misleading results.

Today, I’m sharing the four mistakes I see most often, which are relevant whether you have hyperthyroidism or Hashimoto’s. I’m talking about the importance of testing more than just TSH and T4 levels, why you shouldn’t take biotin or exercise intensely before a blood draw, the need for regular monitoring of thyroid antibodies, how you can get the tests you need, and more.

Convincing doctors to order these tests can be challenging, but don’t be disheartened. Stand up for your health and ask for what you need. Enjoy the episode!


During this episode, you’ll learn about:

  • Mistake #1: Only Testing TSH and T4
    • The various markers that should be tested in a full thyroid panel
    • When to test thyroid antibodies
    • Why it’s crucial to address the autoimmune component of hyperthyroidism
    • Understanding the role of reverse T3 and when testing would be insightful
    • Other relevant non-thyroid tests which I recommend
  • Mistake #2: Taking Biotin Before a Blood Draw
    • How biotin interferences with thyroid blood tests
    • Stop biotin consumption for at least 5 to 7 days prior to your blood draw
  • Mistake #3: Exercising Before Your Blood Draw
    • Exercising too intensely can interfere with thyroid test results
    • Avoid anything more than light walking
  • Mistake #4: Not Monitoring Thyroid Antibodies
  • Monitoring thyroid antibodies is essential for autoimmune thyroid conditions
    • How long to continue monitoring thyroid antibodies
    • Why most people probably don’t need to supplement with biotin
    • Convincing your doctor to order additional blood tests
  • What to consider when it comes to the frequency of monitoring thyroid antibodies
  • How often to retest thyroid markers after restoring your health

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Here is the transcript for this episode:

Let’s discuss four common thyroid blood test imstakes, starting with mistake #1, which is only testing the TSH and T4. Many medical doctors only test for the TSH. TSH is a thyroid stimulating hormone, which is a pituitary hormone. On the other hand, some practitioners will test for the TSH and the T4. Sometimes, the free T4. Sometimes, the total T4.

At the very least, you want to test not only for TSH, but also the thyroid hormones. I like to look at free T4, free T3, especially those with hyperthyroidism. If someone has hypothyroidism, I still like to look at free T3 and free T4, but there is an argument to look at the total hormones. With hyperthyroidism, it usually doesn’t matter. Everything is going to be elevated.

Then the thyroid antibodies, you also want to look at. Thyroid peroxidase (TPOs), these are the most common antibodies. They are more closely associated with Hashimoto’s although a lot of people with Graves’ also have elevated TPO antibodies.

There are thyroglobulin antibodies. These are definitely more associated with Hashimoto’s.

Then there are thyroid stimulating immunoglobulins (TSIs). These are a type of TSH receptor antibody (TRABs). If someone is suspected to have Hashimoto’s, it depends on the doctor. Sometimes, they will just look at the thyroid panel. But if you are looking at antibodies, usually they will test for TPOs. Sometimes, they will test thyroid globulins. Ideally, you want to test both of those.

For Graves’, most of the time, they will look at the TSIs. Some will test the TRABs. The problem with testing TRABs is there are a couple of different types. There is the TSIs as well as thyroid blocking antibodies. More specific to Graves’ is the TSI. That is what I got tested for when I dealt with Graves’, and that’s what most people get tested for. 

If someone has hyperthyroidism in the presence of elevated TRABs, that is typically diagnostic of Graves’. 

Getting back to mistake #1. You don’t want just to test TSH and T4. You want to look at the thyroid panel. You want to look at the antibodies.

Another question you might have is: Do you need to test for all of the antibodies? If you have elevated TSH, let’s say the thyroid hormones are lower, and let’s say then you want to test the antibodies. That’s usually what happens. When you go to a primary care doctor, they will just do a thyroid panel. Or they will do a TSH and see an elevated TSH, which is more closely associated with Hashimoto’s. 

In that case, if you are going to go for a full thyroid panel and antibodies, do you need to test all of these antibodies if you are maybe suspecting Hashimoto’s? I think it depends on the situation. If someone is suspecting Hashimoto’s, I think in most cases, okay just to test TPOs and thyroid globulins, not necessarily TSIs. If there is no history of hyperthyroidism at all, it’s not going to hurt to test the TSIs, but I don’t know if everybody needs to test those.

If someone has hyperthyroidism, and they haven’t yet been diagnosed with Graves’, then you definitely want to look at the TSIs, or you could argue the TRABs. Do you need to test for the TPOs and/or the thyroid globulins? You don’t have to, but you need to keep in mind that some people with Graves’ do have the TPOs and/or thyroid globulins. 

To be fair, it’s not going to change the approach. If you have an autoimmune component, you want to find and remove triggers and do things to heal the gut. Being aware of it could be important. Let’s say you have hyperthyroidism, and you have Graves’ with elevated TSI, but you also have either the TPO antibodies and/or the thyroid globulins. That means the immune system could potentially damage the thyroid gland. Over time, you could become hypothyroid. That is assuming you’re not doing anything to address the autoimmune component, which hopefully you will do if you have Graves’ or Hashimoto’s.

If you have elevated TSH and thyroid hormone low or on the lower side, then just looking at those TPOs and the thyroglobulin antibodies is a good idea. I would say TSI is more optional. 

If you have hyperthyroidism, you want to look at the TSIs. I’d say not a bad idea also to look at the TPOs and thyroid globulins. I would say on the more optional side still because it won’t change the approach. Hopefully, you won’t become hypo if you’re addressing the autoimmune component, but it’s still nice to be aware.

Another reason to look at the antibodies is sometimes, one antibody will lower and normalize when taking a natural treatment approach. You will see TSI lower and eventually normalize, but maybe if you have elevated TPOs, they will stay high. Maybe you’re missing something if one antibody normalizes, but another one- Let’s say you just do two. If one lowers, and the other normalizes. Or if you test all three, and two of them normalize, but you still have one elevated, you could have different triggers for different antibodies. 

Should you test for reverse T3? T4 converts into T3, and T3 is the active form of thyroid hormone. Reverse T3 is the inactive form of thyroid hormone, specifically of thyroxine, T4. 

For those with hyperthyroidism, I no longer test reverse T3 because most people will be elevated, and it’s not really giving us any information. 

With Hashimoto’s, or non-autoimmune hypothyroidism, it’s not a bad idea to look at reverse T3. If someone has elevated reverse T3 in the presence of Hashimoto’s, then they might have an issue converting T4 into T3. You can also look at the actual thyroid hormones and usually tell that as well. 

Again, it’s something I don’t test for with hyperthyroidism, but I do test for Hashimoto’s. Is it absolutely necessary with Hashimoto’s? Some would say yes, and some would say no. I definitely don’t recommend it for hyperthyroidism.

I won’t get into any blood tests in detail here. The mistake is just looking at TSH and T4. It goes without saying that yes, you want to do a thyroid panel with antibodies. 

You want to look at other tests, too. At the very least, doing things like a complete blood count (CBC) with differential, comprehensive metabolic panel, lipid panel, 25 hydroxy Vitamin D. 

I recommend a complete iron panel, not just ferritin or iron, but looking at iron, ferritin, iron saturation, total iron binding capacity, and Vitamin B12. Serum B12, I usually recommend, but to be fair, it’s not the best marker. It’s the marker most doctors are most likely to test for. There is one, methylmalonic acid, that you can test through the blood or urine. Typically, through the urine is preferred. It is a better marker.

There is homocysteine. There is CRP, which stands for C reactive protein. I usually recommend high sensitivity CRP. 

There are other tests I will recommend. I won’t get into great detail here. Usually, you do want to go beyond thyroid and thyroid antibody testing.

Let’s talk about mistake #2, which is taking biotin prior to the blood draw. Biotin, which is found in multivitamins, B complex supplements. You could also take a separate biotin supplement. The problem is that biotin can interfere with a thyroid blood test. Usually, what it will do is cause a false high free T4 and free T3 and false low TSH. Essentially, you might look like you have hyperthyroidism when you don’t. If you already have hyperthyroidism, maybe it will look worse than it actually is because you’re taking biotin. You want to be cautious about taking biotin.

Also, I know when you visit Lab Corps’ website, they will also say not to take it if you’re measuring all three antibodies. I’m not sure what effect it has specifically on the antibodies. On their website, they say to avoid biotin when doing anything thyroid-related. If you visit Lab Corps, it says, “This test may exhibit interference when a sample is collected from a person who is consuming a supplement with a high dose of biotin. Patients should be cautious to stop biotin consumption at least 72 hours prior to the collection of a sample.” If you are taking a high dose biotin supplement, or another supplement that has a high amount of biotin, you want to stop it for at least 72 hours. 

That brings up the question: What Is considered to be a high dose of biotin? It really doesn’t clarify. It doesn’t give specifics. If you’re taking a separate biotin supplement, like 1,000mcg or 5,000mcg- I would say longer than 72 hours. It says at least 72 hours. Some sources will say longer than that. If someone is taking a biotin supplement, 72 hours, or three days, might be sufficient. To play it safe, maybe go like 5-7 days. 

If you have biotin in a multivitamin or part of a B complex, maybe 100mcg or a couple of hundred mcg, three days probably will be enough. You might not need to avoid it at all just because that’s probably not considered to be a high dose. I would say just to play it safe, you might want to stop taking your B complex if it has biotin 72 hours prior to getting a blood draw. Whether it’s in a multivitamin or B complex, doesn’t make a difference. Avoid it for a few days. 

Mistake #3: Exercising prior to the blood draw. Exercising too intensely can interfere with thyroid test results. You do want to be cautious. The question is what is considered to be too intense? I will say that light walking should be fine prior to doing a blood draw. Otherwise, I would refrain from both resistance exercise and cardiovascular exercise. Walking is cardiovascular exercise. Jogging, running, going on an elliptical machine, riding your bike could also be- In some cases, it could be extreme, but in many cases, it’s not. I would say just to play it safe, refrain from most cardiovascular activities. 

Same thing with resistance exercise. If you are doing light weightlifting, you might be okay. I would say still, it’s not like you’re getting a blood test every week in most cases. If you’re getting a blood test once a month or once every couple of months, just plan it where that morning, you’re taking it easy, and you’re not doing anything that is overexerting yourself. 

I should say probably not just slight walking or exercise, but other activities, like sexual intercourse, you might not want to do that prior to doing a blood draw. There is not research showing that it will interfere. Exercise, there are some studies that show that exercise will. To me, if that might be something, that could. That one day, once every month or once every couple of months, I would say just take it easy that morning of the blood draw. 

Now, the fourth and final mistake: Not monitoring the thyroid antibodies. I of course mentioned you want to make sure to test them in mistake #1. Many medical doctors will test the thyroid antibodies but will only do so initially. Let’s say they do a TSH or TSH + T4, and they discover that someone has an elevated TSH or depressed TSH and elevated T4. In that case, they are then more likely to test the antibodies. 

Sometimes, that’s all they’ll do. They will just do that single test, and their argument is that they’re not doing anything for the immune system. All they’re doing is managing the thyroid. In the case of Hashimoto’s, they’re just giving thyroid hormone replacement, either levothyroxine or desiccated thyroid, usually levothyroxine with a conventional medical doctor. In the case of hyperthyroidism, methimazole or a beta blocker. In some cases, radioactive iodine or thyroid surgery. Either way, they are not doing anything for the immune system in the cases of autoimmunity.

There are some practitioners who are willing to test these antibodies every now and then, maybe once or twice a year. Sometimes, it’s to keep an eye on them. Sometimes, it’s to make the patient happy. If the patient asks for them, they might say, “Okay, we could do it once a year, just to look at them.” They might do that because they are concerned about insurance.

Insurance is all about justification. The insurance companies don’t want any practitioner to do unnecessary testing. If someone has elevated antibodies, and they test it again a few months later, and do it every few months, insurance usually won’t reject that. They don’t have the same philosophy as conventional medical doctors, meaning that in this situation at least, where they shouldn’t focus on the immune system, quite frankly, they don’t understand thyroid health or thyroid immunity. 

If someone did antibodies, and everything was negative, and then someone wanted to test them every few months, then they would red flag it because everything is normal, so why keep on testing? You could make the argument if you are doing things to address the immune system- The medical doctors aren’t doing that. I don’t think the insurance companies know that. 

My point is if you have health insurance, and your doctor doesn’t want to test for it because they are worried about insurance, it’s up to you. If it were me, I’d like to take the chance and have it run through insurance and see. 

Obviously, another option is to pay out of pocket. I know the antibodies could be more pricey than doing other types of tests. I’m not saying you have to do it every month or even every couple of months in every single situation. I think once a year, even twice a year, it’s going too long if you’re trying to monitor the antibodies, which is the mistake that we’re talking about here. Most medical doctors aren’t doing this.

Over time, you want to see those thyroid antibodies decrease and normalize. It might not be a smooth process, meaning you might get a rollercoaster effect. Sometimes, you will see the antibodies decreasing. They might go up, down, up, down. For numerous reasons, if you are exposed to a trigger, they might go up pretty high. Ideally, you want to see them decrease and normalize eventually.

Getting back to how frequently you should monitor the thyroid antibodies. As I mentioned, you don’t necessarily have to do it every month. If you do it every other month, that’s great. Even if you do it every 3-4 months, in some situations, that’s going too long. But it’s better than doing it every six months or once a year. 

If you get a thyroid panel every 6-8 weeks, and you do thyroid antibodies every time you do a thyroid panel, that’s great. If you’re paying out of pocket, and you don’t want to do it every time you do a thyroid panel, at least do it every other time, to keep an eye on the antibodies. 

Let’s go ahead and summarize what I discussed here: The first mistake is just testing the TSH and free T4. At the very least, you want to test for TSH, free T4, free T3, and thyroid antibodies. 

Mistake #2 is taking biotin prior to doing a blood draw. Biotin can interfere with thyroid blood tests, as it can cause false high free T4 and free T3 readings as well as a false low TSH. 

Mistake #3 is exercising especially intensely prior to doing a blood draw. Exercising too intensely can interfere with thyroid test results.

Mistake #4 has to do with not monitoring the antibodies. Since Graves’ and Hashimoto’s are autoimmune conditions, you want to monitor the thyroid antibodies on a consistent basis. Not necessarily every month. Every other month is great. Even if you do it every other thyroid panel, that’s also acceptable.

Those are the four common thyroid blood test mistakes. There might be other mistakes, but those are the ones I wanted to focus on. Hopefully, you found this to be valuable. As usual, I look forward to catching you in the next episode.