A Small Number of Thyroid Patients Cannot Cope with Any Amount of Levothyroxine (T4 medication) in Their System

This blog came out of a conversation with a thyroid patient who was still having some issues when on mostly T3 with a little T4 in the mix. She had improved greatly with the T3 but was not quite at the point she wanted to be.

I related my own story to her. I simply cannot cope with even small amounts of T4 medication, e.g. even 5 mcg of T4 begins to make me feel ill with returning hypothyroid symptoms and signs after one week. This is the case even when my T3 dosage has not been lowered.

I have seen this type of situation many times before. It is very clear to me that some people simply cannot cope with anything but small amounts of T4, and in a few cases, any T4 at all makes them feel worse.

The thyroid patient then asked me about FT3, FT4 and reverse T3 results. She wanted to know if the above issue could still be the case even if the numbers were all within the reference ranges and rT3 itself was not high. She said she was only taking some T4 to keep her doctor happy because he felt that everyone needs to have some T4.

Laboratory test results do not explain everything. In fact, having ‘in range’ lab results simply does not work for some people who have more complicated thyroid hormone metabolic issues. Lab ranges have been developed based on a huge number of people. Those patients who have unusual issues may not feel well when their results fit into the standard reference ranges. Lab test results show blood levels of thyroid hormones. They cannot show exactly how effective the active thyroid hormone T3 is at the nuclear thyroid receptors and the mitochondria – there is currently no blood test that can show this.

Everyone needs to have enough T3 thyroid hormone working at the nuclear thyroid receptors. T4 does not bind to the nuclear thyroid receptors and it does very little. The main value of T4 is to be converted to T3. Only the T3 thyroid hormone binds to the nuclear thyroid receptors, as it is the active thyroid hormone. For example, those people with absolutely dreadful T4 to T3 conversion issues may find T4 leaves them woefully hypothyroid even when combined with T3. Atrophic thyroiditis (AT) is another example of a condition that can make the use of T4 extremely difficult, as it often causes highly variable conversion rates of T4 to T3, inducing swings from hypothyroidism to hyperthyroidism (more information about AT at the end of this post).

I explained to the thyroid patient that I did not know that this issue was definitely what was holding her back, simply that it could be.

I do believe that this issue is one of the reasons why a small number of people never fully recover until the very last vestiges of FT4 and rT3 clear out. I have seen this work successfully many times with thyroid patients on T3-Only therapy. It is not a common issue but it does apply to some patients.

In my own case, over the past 25 years, I have tested whether I can cope with any T4 medication about ten times. I wanted to do this in case something had changed. Each time I have added even tiny amounts of T4 meds the same thing has happened. This is without reducing the T3 at all.

Here is an extract from Chapter 10 in the Recovering with T3 book:


There have been occasions when I wanted to discover whether anything had changed in the way T4 worked in my body. However, whenever I have attempted to use T4 replacement therapy again, it still failed and I quickly became very ill.

T4 still does not suit me – even in small additional amounts to my T3, e.g. 12.5 mcg per day of T4 is not tolerated by me.

T4 in any quantity brings back my hypothyroid symptoms. I am healthy, fit, active and symptom-free whilst on T3 replacement therapy. However, sometimes people express views like, “everyone needs some T4”. These types of views are stated from time to time, usually by doctors, but also, sometimes by thyroid patients. Unsurprisingly, the patients concerned are on some form of T4 based medication, and they think everyone else should be taking it too.

Sometimes this viewpoint is based on an old and not especially compelling piece of research that attempts to show that T3 cannot be used in the brain. Then they extrapolate from there that everyone needs T4. This is not the case. One of the big flaws in that type of argument is that people who are living well on T3 alone have not been studied for the very likely compensatory adjustments that the body makes when using T3 on its own.

The second big flaw is that more research is being found all the time to overturn old research. The ‘brain requires T4 research’ has just been proved wrong in fact. The new research is changing the entire understanding with its discovery of active transporters. [2] There are T3 transporters and they are more active in adult life. So, circulating T3 is a source of T3 for the brain. It is definitely not dependent on T4 in adults. Older assumptions are being proven wrong all the time. This particular assumption had to be wrong anyway – as thousands of people on T3 replacement therapy are well and healthy.

I have used T3 replacement for over twenty years. I know many thyroid patients, who have recovered their health using T3 replacement and have been using it for a long time.

T3 replacement therapy can be a very effective, safe, long-term thyroid hormone treatment.”

See this blog post on T4 not being required in the brain:

All of the above may seem a very heretical viewpoint to some thyroid patients who do very well on natural desiccated thyroid or a T4 combination. Even some who are on only a little T3 and rely on their own thyroid for T4 and T3 may find the above to be far-fetched. Well, all I can say is that I have lived my life in my own body and I know that the above is utterly true. I have also seen it in other thyroid patients who have near-miraculous recoveries when they are on T3-Only and have no T4 left in their systems.
We are not all the same. We have various issues. I am very pro-Levothyroxine (T4-Only) for those patients that convert it well to T3. T4/T3 combinations also work extremely well for many. This post is really just to make it clear how wide the spectrum of needs can actually be. I ask those that think the above is nonsense to simply not just think from their own experience.
We are not all the same. Some people cannot cope with ANY T4 in their system at all. It can be the thing that prevents them from recovering their health. Clearly, very poor conversion from T4 to T3 may be a factor for many in the same category. However, I do not rule out other more complicated problems, which may eventually become clear through research.

Finally, one big issue is that doctors and endocrinologists generally have strong views that FT4 levels need to be in range and T3 medication is not needed. For them, having no T4 meds or having any T3 meds is tantamount to having your window open at night and encouraging the Boogieman to come in through the window. They cannot cope with the notion of not taking T4 or of taking T3. They have been taught their views in medical school and are usually very rigid in holding this view. This is why some thyroid patients, who feel much better on T3-Only medication, get told by their doctors that they need to have some T4 (even if they do not seem to tolerate T4 medication well).

Until medical training begins to acknowledge some of the newer research regarding TSH and the importance of T3, and that thyroid patients are not all the same, then patients will still keep facing archaic views that keep many of them sick.

Best wishes,



In general, I still hold the view that T3-Only therapy is the treatment of last resort. I am very positive about the use of T4/Levothyroxine for a lot of thyroid patients who convert T4 well. T4/T3 combination therapy works extremely well for many patients. I just know that some thyroid patients need T3 with no T4 in order to recover. See this blog post for more details on my viewpoint:

Here is a blog post about Atrophic Thyroiditis:

Paul Robinson

Paul Robinson is a British author and thyroid patient advocate. The focus of his books and work is on helping patients recover from hypothyroidism. Paul has accumulated a wealth of knowledge on thyroid and adrenal dysfunction and their treatment. His three books cover all of this.

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  1. Dorathy Griffith on 11th June 2022 at 7:22 pm

    I have a question. I did feel better with your t3 protocol but don’t have complete resolution. Seems like I need higher dosing. How can I get help obtaining t3 more than 25mg tid? Also have to take Prednisone to function and dhea, low testosterone.

    • Paul Robinson on 12th June 2022 at 10:54 am

      Hi Dorathy, I usually recommend that people try asking other thyroid patients on thyroid forums for information on doctors or functional medicine doctors who will prescribe T3 or other solutions that they could look into. Your current dosage is quite low so I can easily imagine that you might need a higher dosage.
      Best wishes, Paul

  2. gailen on 12th June 2022 at 11:29 am

    Do you work with people to help them?

    • Paul Robinson on 12th June 2022 at 11:55 am

      Hi Gailen, occasionally yes. I have been taking some time off but then contracted Covid (again, courtesy of a relative this time). So, I’m not doing anything right now. If interested in the future then use the Contact Us form on the homepage of this website.
      Best wishes, Paul

  3. Maria on 13th July 2022 at 5:07 pm

    Hello from Germany,
    I hope you are better 🙂

    I take T4 for 10 years and never felt better or healthy. I have these hypothyroidsm symptoms since I am 14 (now I am 41) and this cannot be the way.
    My thyroid went from 6 ml to 3 ml in this 10 years and is labeled as “hashi seronegative” or “few peoples thyroid just shrinks”. I have no antibodies. So I am not even fitting in the AT category. I sometimes loose some issues for a few days when increasing the dosage but they return quickly, no matter the range of the lab. My TSH is always 0.01. I could swear there is nothing really intracellular. FT3 and FT4 conversion is ok. Do you have any idea what this sounds like? TYVM

    • Paul Robinson on 13th July 2022 at 5:52 pm

      Any thyroid volume less than 5 ml is likely to be atrophic thyroiditis. Hashimoto’s does not cause loss of thyroid volume – just fibrosis.

      Even an FT3 in the range may not be high enough for some people.

      If you have never tried T3 in 10 years then I’d say that you’ve waited long enough to switch to less T4 and more T3. Maybe even just T3.
      It can be a game changer.

      Low TSH will always mean that your conversion from T4 to T3 is minimised to the lowest it can be.

      It actually does sound like potentially AT to me. If this is the case T3-Only therapy is the best option.

      Good luck!

      Best wishes, Paul

  4. Susan Campbell Dargie on 27th August 2022 at 9:28 pm

    Hello Paul
    I read with huge interest your posts. I have Graves Disease and have been so ill on Levothyroxine. Terrible, I feel like I am stuck in some awful nightmare. Taking Thyroid armour in tiny doses with huge antihistamine.
    Gp and Endocronoligist do not have a clue as to what to do with me. I am totally allergic it wld seem!
    Very scary and I feel totally ill all the time.

    • Paul Robinson on 28th August 2022 at 11:15 am

      Hi Susan, you don’t say whether you have had RAI for the Graves OR how it has been treated. However, because you are now on Levo I assume the situation has been dealt with and it has thrown you into hypothyroidism.

      If your thyroid has had RAI then you will have lost a considerable amount of conversion ability from T4 to T3. The thyroid gland is the most important converter and generator of T3 in the body. Levo generally does not replace enough T3 for those without a whole working thyroid gland.

      I would read my The Thyroid Patient’s Manual book as it will explain more, including how to test things properly and what your best treatment options are. A lot depends on full lab test results – which you may or may not be getting. See the book for details.

      Often, people in your situation need to be on T4/T3 and not mostly T4 meds.

      I hope this helps a little.

      Best wishes, Paul

  5. Vicki S on 27th January 2023 at 1:02 am

    I do not tolerate any T4 at all. My dr is ok with this but can’t seem to understand this. I may bring up being deficient in that enzyme which I can’t think of.

    As soon as I take T4, I feel heart palpitations, heavy chest, anxious, and an overall feeling of doom. Because this reaction happens so quickly, I do wonder if it’s some sort of allergy to a filler in the medication. I have taken a few different brands. What are your thoughts?

    I’ve just learned of your CT3M, because I’m looking into trying to wean from HC. Just purchased two of your books.

    • Paul Robinson on 27th January 2023 at 10:19 am

      Hi Vicki,

      You aren’t alone in this and it doesn’t have to be an allergy.

      It can simply be poor conversion. For some people, a working thyroid gland contributes in the neighbourhood of 25% of the needed T3. In a few that figure can go up to 60% through conversion and native production of T3.

      Losing thyroid function for people highly dependent on the thyroid often means that T4 does not produce sufficient FT3 and instead that T4 is converted into reverse T3 which can make people feel awful.

      I can’t tolerate even 10 mcg of T4 and I know many like me.

      I hope this helps.

      Best wishes, Paul

  6. Jennifer on 13th July 2023 at 3:28 am

    Thank you for your information. I have struggled with Hashimoto’s for 21 years. I’ve never felt much better on T4. After doing some researching I asked my Nurse Practitioner at Mayo Clinic if she could test my FT3 because I had read that sometimes T4 doesn’t convert to T3, even with a normal TSH. She explained to me how the TSH was an accurate test, but that she’d order the T3 testing. WELL, my T4 was really high and my T3 was really low. She then changed my Levo to 88mcg and added a weekly increasing dosage of T3, up to 75 mcg. I rechecked labs in 6 weeks and T3 was too high. Now I’m on the 88 Levo and 50 T3. I still feel like it’s too much, but we’ll recheck in 6 weeks. We’ll see how it goes.
    Just goes to show that even those at Mayo Clinic don’t get that TSH isn’t the end-all be-all. 🙁

    • Paul Robinson on 13th July 2023 at 9:45 am

      You may need to get TSH, FT4, FT3 and Reverse T3 tested. When you are a poor converter and you add T3 to T4 treatment, often more of the T4 goes into reverse T3. This is a bad thing as it can hinder the T3 from working. I would also consider getting my The Thyroid Patient’s Manual – it will give you the information to argue your case more.


      You might need lower T4 and slightly lower T3 also. 50 mcg of T3 can be a full replacement dose for some people. I have no thyroid. I don’t take any T4 meds so my FT4 is zero and I only take 60 mcg of T3. So, you could easily have the wrong balance of meds – but without testing rT3 also you won’t know.

      The book will help – a lot!

      Best wishes, Paul

  7. Maricela Alers on 2nd September 2023 at 10:51 pm

    I think that is my case, I have never been able to increase the dose of levothyroxine, I feel hyperthyroid after two weeks of taking it. I changed to half of grain of NDT and the same thing happens to me. Currently I started with the CT3M method and I feel better, but I kept taking half a grain of NDT and I still have many symptoms. I have decided to drop NDT and include only T3, but my question is: Could T3 make me anxious? That is one of the main symptoms that I suffer when I increase the dose of levothyroxine or NDT and I am afraid that it will cause me anxiety.
    My thyroid labs are always in the normal range but borderline low, and my latest cortisol is low.

    • Paul Robinson on 3rd September 2023 at 9:55 am

      Low cortisol combined with thyroid treatment causes anxiety. It actually causes the body to make adrenaline to compensate for the missing cortisol. I would focus on T3 only and get the CT3M dose adjusted properly. The Recovering with T3 book has the full protocol for doing this.
      Being in the reference range doesn’t mean you are normal. The ‘normal’ range refers to a Gaussian distribution – which is a statistical term. Most people are in the middle of the range with very few who are healthy being in the low part of it.
      Thyroid patients often need to have FT3 in the upper half of the range.
      Good luck!
      Best wishes, Paul

  8. Rebekah on 23rd January 2024 at 9:02 am

    Hi – I’ve read this post with interest and bought the T3 recovery manual. Only just started reading. I’m hypothyroid and currently building my NDT dose up following a move from T4 only. I felt steady progress at first on the lower doses but, since reaching 2 grains, I’m really struggling with feeling very ill, weak, cold, poor appetite, insomnia etc. If I break from it for 24 hours I feel relief before the hypo symptoms return. Overall very little progress is felt now. Previous lab results suggest I am a very poor converter. Are you available for coaching? I’ve also sent a message using my email address.

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