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We already know that in order to be diagnosed with Hashimoto’s (the leading cause of hypothyroidism at 90%), a positive antibody test is usually indicated. 
Testing for Thyroid Peroxidase Antibodies and Thyroglobulin Antibodies (TpoAB and TbAB) and them coming back with results above range is how we know if we have this autoimmune condition.
But did you know that you can still have Hashimoto’s, without the positive antibodies?
Negative Antibodies Do Not Mean You’re Off The Hook
Yes, negative antibodies doesn’t necessarily mean you don’t have the autoimmune condition Hashimoto’s and because we know that it is responsible for 90% of us with hypothyroidism, that leaves up to 10% of those with hypothyroidism, having Hashimoto’s but coming back negative on antibody tests.
Having Hashimoto’s without positive antibody tests is known as seronegative autoimmune thyroiditis, or serum negative Hashimoto’s.
How Could I Still Have Hashimoto’s?
Firstly, it’s important to be aware that your antibodies can move up and down regularly and so testing them often or at least a couple of times a year is beneficial when keeping an eye on things. Theoretically, you could test negative for thyroid antibodies one week and positive the next week.
This is because, as the thyroid gland is being attacked and losing function (causing hypothyroidism), extra thyroid hormone contained in thyroid cells are released into the bloodstream in bursts, which can lead to hyperthyroid symptoms and Free T3 and Free T4 levels to go up (even above range), along with fluctuating antibody levels.
Therefore, if you experience your results moving up and down, even without thyroid antibodies, you can probably safely assume that you have Hashimoto’s as it’s quite a common sign of the condition.
It’s also important to know that lifestyle changes and interventions such as a gluten-free diet, dairy-free diet, selenium supplementation  and Vitamin D supplementation , can also reduce antibodies.
I saw a dramatic reduction in my own antibodies from >1300 to 200, from implementing these four things alone. I also eventually got my Hashimoto’s into remission.
So if you’re already implementing things that can reduce thyroid antibodies, then when it comes to testing them, antibodies could come back as being quite low and even so low that it might appear you don’t have Hashimoto’s at all, even when they would be high if you weren’t implementing antibody reducing interventions.
This is where it could actually be beneficial to stop any supplement and diet changes, for example resume eating gluten and dairy again and stopping the selenium and Vitamin D supplements, and then retesting a few weeks later to see if the amount of antibodies change and do indeed indicate Hashimoto’s.
However, some people may always test negative for Hashimoto’s on antibody panels, even when they’ve ran the tests numerous times, having not implemented any lifestyle changes than can bring the antibodies down, yet examinations and biopsies of the thyroid gland confirm that Hashimoto’s is present, due to the visible damage.
This could be due to their overall immune system being so weak that they simply don’t produce many, if any, antibodies. You need a certain amount of good immune function in order to produce them, however, total white blood cells and B-cells could be too low to produce antibodies. And thus, it may take until the compromised immune system starts to recover and the individual starts to feel more well overall, for production of thyroid antibodies to start.
If you’ve tried going gluten-free for example, only to find that your antibodies go up yet you feel better for it, this could be you. Immune health may be restored enough so that thyroid antibodies have begun being produced again, due to this intervention improving your health.
What Can I Do?
Seeing as most of us with hypothyroidism will have Hashimoto’s anyway, it may be best to assume you do have the autoimmune condition for at least a while, and implement things such as diet changes (gluten-free especially), supplementation and other lifestyle changes, and see if they help you.
If they do, it might be a sign that you do indeed have the autoimmune condition as these interventions are so well reported in helping to control it. Remembering that test results which move up and down can be a sign of Hashimoto’s and the on going destruction too, even with positive antibody tests.
You can order your own testing for Hashimoto’s in the UK here and worldwide here.
Related Article: Why It’s Important to Know if You Have Hashimoto’s
Do you test negative for thyroid antibodies?
You can click on the hyperlinks in the above post to learn more and see references to information given.
ChloeJanuary 20, 2023 at 9:46 pm
Hi..I’m 48 and last year I found out that I have a thyroid nodule and Hashimoto’s..based on ultrasound and I have the TPO antibodies. January of 2022-I had 63.9, and last week I had blood work again-and it went way down to just 17.8. The 63.9 was low to begin with-so I don’t know if I’m really sensitive to gluten-b/c the 63.9 was when I was having lots of stuff that had gluten in it. I’m vegan for almost 14 years…but I went gluten free since last February. My thyroid function is still normal…so I don’t need meds yet. I have to keep getting annual ultrasounds now to check if my nodule within my right lobe is stable. My Dr told me that b/c of the antibodies being present, and the ultrasound report-it suggests that I have Hashimoto’s. I just got my blood work results two days ago-and was surprised that my TPO went down to 17.8. I didn’t talk to my Dr yet about it, but sent him a message in my portal. Does it mean that I have Serum-negative Hashimoto’s now? I’ve had two ultrasounds so far…the report says that it’s heterogeneous hypervascular…and my nodule is Isoechoic. My vit D level is 77.
MariselaJuly 24, 2020 at 3:25 am
I’ve heard an ultrasound of the thyroid is the surest way to confirm if you have Hashimoto’s- is that true?
DianeMay 9, 2019 at 1:42 pm
I have tested negative for Hashimoto; does this mean I don’t have it? My doctor said I don’t; I’m confused on if I have it anyway I tested negative; how do I know for sure?
Rachel HillMay 9, 2019 at 2:30 pm
Hi Diane, I can’t give you a definitive answer unfortunately. As the article explains, some people with Hashi’s still test negatively for it even though they still have it. If you’re currently doing anything that can lower antibodies such as being gluten-free, taking selenium, Vitamin D etc. then these could lower them so that it looks like you don’t have Hashi’s. Also, your immune system may be so weak that you’re not producing them. Only you will know this information.