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Thyroid UK
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Poor conversion of T4 to T3

Hi thanks for letting me join. Since being diagnosed with underactive thyroid in 2010 my conversion of T4 to T3 is very poor so I am looking to add T3. How do I obtain this please? Current dose 175mcg Levothyroxine.

Thank you!

SEP-2017 (175mcg Levothyroxine)

Serum TSH 1.20 (0.2 - 4.2)

Serum Free T4 19.1 (12 - 22)

Serum Free T3 3.3 (3.1 - 6.8)

9 Replies


Before adding T3 it's important that nutrient levels are optimal, no thyroid hormone can work if vitamins and minerals aren't at optimal levels. Have you had them tested:

Vit D




And have you had thyroid antibodies tested - Thyroid Peroxidase and Thyroglobulin?


Thyroglobulin antibodies 376 (<115)

Thyroid peroxidase antibodies 285.3 (<34)



So your high antibodies confirm autoimmune thyroiditis aka Hashimoto's which is where antibodies attack the thyroid and gradually destroy it. Has anyone told you this? When antibodies attack it causes fluctuations in symptoms and test results.

Most doctors attach little or no importance to antibodies and don't understand how they affect the patient. We have to read, learn and help ourselves where Hashi's is concerned.

You can help reduce the antibodies by adopting a strict gluten free diet which has helped many members here. Gluten contains gliadin which is a protein thought to trigger antibody attacks. Also, supplementing with selenium L-selenomethionine 200mcg daily can help reduce antibodies, as can keeping TSH suppressed.






Hashi's and gut/absorption problems tend to go hand in hand and very often low nutrient levels are the result. You need to test those vitamins and minerals listed above as it's very likely your levels are either low or deficient and they need to be optimised for thyroid hormone to work and before considering adding T3. Post your results when you have them for comment.


Hi thanks no my GP hasn't told me I have Hashimotos, she said I have hyperthyroidism? I had vitamins and minerals tested last week, I don't know what they are.



If you were diagnosed with underactive thyroid in 2010 and have been on Levo all this time, there is absolutely no way you can have hypERthyroidism, it's impossible.

Your GP is showing that she doesn't know anything about Hashi's.

What can happen is that the fluctuations caused by the antibody attacks can show hyper-type symptoms and test results, they're called Hashi's Flares or Hashi's Swings, but these are temporary. When the antibodies attack they dump a load of thyroid hormone into the blood, which causes this but eventually things go back to normal. It can help to adjust dose of levo during these times, but readjustment will be necessary when things settle down again.

You should address the Hashi's as mentioned above, read the links so you can understand and you may be able to educate your GP!

You need to ask your surgery for a print out of your vitamin and mineral results, don't accept hand written or verbal results (mistakes can be made), get a print out, ensure the ranges are included, then post on the forum for further comment.


LDN has been a life saver for me with hashimotos. If you can find a clued up GP or go private who is willing to prescribe you LDN then it’s totally worth it. Going gluten & dairy free is also advisable along with checking all your vitamins & minerals as per above advice. You have an autoimmune disease which means addressing the gut is the most important factor in healing. Seek out a nutritional therapist or naturopath who can advise a plan with reccommended supplements. I now take collagen, tiger nut, probiotics, b12, vitamin D, selenium, zinc & bone broth now and again. Oh and fermented foods. A stool test is useful for checking for any underlining viruses/bacteria’s.


Hi I have results of vitamins and minerals do I post thank you


Yes, include the ranges and say if you are supplementing anything and the dose.


Hashimoto's affects the gut and leads to low stomach acid and then low vitamin levels

Low vitamin levels stop Thyroid hormone working

Poor gut function can lead leaky gut (literally holes in gut wall) this can cause food intolerances. Most common by far is gluten

According to Izabella Wentz the Thyroid Pharmacist approx 5% with Hashimoto's are coeliac, but over 80% find gluten free diet helps significantly. Either due to direct gluten intolerance (no test available) or due to leaky gut and gluten causing molecular mimicry (see Amy Myers link)

But don't be surprised that GP or endo never mention gut, gluten or low vitamins. Hashimoto's is very poorly understood

Changing to a strictly gluten free diet may help reduce symptoms, help gut heal and slowly lower TPO antibodies







Just seen your vitamin post. They all need improving.

Healing gut and better vitamins are essential first, before looking at adding T3



Other things to help heal gut lining

Bone broth




Importance of magnesium


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