Thyroid UK
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T3 - advice on taking a high dose?

Does anyone have experience administering themselves with a (potentially high) dose of T3 and could you advise on any precautions one would need to take on doing so?

Furthermore could anyone recommend which type of T3 (slow-release, cytomel) is better and from which website? Please PM me regarding the latter.

For those interested my reasons for doing so are as follows. Any advice welcome.

I have been treated in the past for depression and bipolar II, however my last treating psychiatrist was convinced my condition was thyroid related (in spite of normal blood tests) and put me on a course of high-dose levothyroxine (rising to 500mcg daily).

I stopped this due to some minor negative side effects towards the upper end of the scale, but wanted to pursue the thyroid avenue further as I felt it was doing some good.

I then tested positive for the faulty DI02 gene, indicating that my symptoms may indeed be thyroid related. My psychiatrist is not interested in T3 and having gotten nowhere with the GP I've decided to procure it online.

I intend to follow the Kelly study (link below) regarding how much to take, and given my experience with levothyroxine I will gradually increase it from a low starting dose of c.10mcg taken before breakfast.

Any advice/experience with regards to any of the above would be very much appreciated.


18 Replies

Hugo, take a look at this psychiatrist's blog. I just did a search on 'Thyroid' and there are several posts. I think the third or fourth down is about T3 and depression. I have found her information to be useful but I am hypothyroid and was taking thyroxine but it did nothing for depression resulting from a friend's suicide. Adding a small amount of liothyronine helps a lot. Unlike you, I have no idea if I have a bad 'gene'. Doubt it since I managed to grow up and I'm 5 feet 9 inches tall.


Thanks gabkad, I'm familiar with this blog. It's useful on the science behind on thyroid function but unfortunately I haven't found much on how best to administer it.

Regarding the faulty gene, the DI02 gene in question is faulty in approx 16% of UK citizens and to my knowledge has no affect on a person's height (I'm 6'3"). What is does mean however is that their enzymes may have a decreased ability to generate the active T3 hormone. As this takes place within the cell, results would not show in blood tests.

My blood test results are perfectly normal but as I've had the faulty gene confirmed I think it's probably wise to try T3 before going down the potentially more dangerous routes that have been recommended to me (antidepressants, anticonvulsants).

The issues I've got are finding a source of T3, making sure it's decent quality, and administering it carefully.


No kidding. I find that your psychiatrist prescribing up to 500 mcg of thyroxine (to minimal effect) to be outrageous. If you weren't getting thoroughly hyper symptoms, then obviously it was doing nothing for one reason or another. The fact that this person won't even trial you on liothyronine is kind of 'duh?' Most doctors of all stripes are totally paranoid of prescribing high doses of just about anything.


Welcome to the forum, hb8847.

Hugo, Normal is a broad range, it would be helpful to see your thyroid results with the lab ref ranges. It's not uncommon for bipolar II and other psychiatric illness to be misdiagnosed due to undiagnosed hypothyroidism.

Impaired DIO2 reduces T4 to T3 conversion and it may be that low doses of T3 are sufficient to enable conversion.

Advice taking any thyroid hormone is to start low and increase dose slowly and, for low thyroid, to take the minimum dose required to render euthyroid. Thyroid patients are advised to have regular thyroid blood tests to check their FT3 in particular is within normal range as long term elevated FT3 increases the risks of atrial fibrillation and osteoporosis. I don't know how this is dealt with when non-thyroidal patients take supraphysiological doses of Levothyroxine (T4) or Liothyronine (T3).

What were the adverse effects you experienced on 500mcg Levothyroxine?


Hi Clutter, thanks for your reply.

My blood test results are as follows.

TSH 1.89 (0.35 - 4.94)

FT3 4.78 (2.63 - 5.70)

FT4 14.1 (9.0 - 22.0)

Regarding my symptoms on levothyroxine, from 400mcg upwards I began to feel breathless when moving about, and heart rate would go up a bit higher than I'd want. Before 400mcg I'd had no effects, either positive or negative. I'd had an ECG performed on each increase and these were all fine.

Regarding the risks of high T3, please correct me if I'm wrong but as far as I'm aware the risks of administering high doses of thyroid medication (HDT) are generally not as severe as the risks of hyperthyroidism. The majority of my research is based on the excellent website, from which I've attached the following quote;

"HDT isn’t hyperthyroidism. HyperT is due to internal production of too much thyroid (official definition) and it does cause a lot of medical complications. With HDT these complications are not there. Why the difference? For our purposes it doesn’t even matter. What the research shows is that HDT works and is not associated with bone thinning or cardiovascular complications.

The largest data comes from HDT used to prevent the return of thyroid cancer, where HDT doesn’t have the complications you see with hyperthyroidism. You can still see side effects of too much but that just means you have to decrease the dose."

That said, I am aware that administering T3 must be done with caution and I wouldn't be considering doing so we're I not at my wits end regarding treatment options.


Hugo, Your thyroid results are within range but FT4 is a little low although FT3 looks reasonable.

400mcg is a hefty dose so I'm not surprised you felt overmedicated but it is surprising you didn't feel it on lower doses.

I'll have a look at link later. I agree with the points in the extract you quoted. I'm a thyCa patient and TSH is suppressed to avoid recurrence. I don't get the dire warnings about suppressed TSH causing AF and osteoporosis so many hypothyroid patients get. I've often thought the warnings about suppressed TSH appear to be extrapolated from studies into hyperthyroidism where TSH is suppressed and FT4 and FT3 are elevated.


Yes I felt nothing on lower doses but presumably this could be explained by the malfunctioning DI02 gene? If I've understood correctly it means I have trouble converting T4 to T3, go giving me more T4 would just raise my Reverse T4 and hypothetically make me feel worse?


Hugo, Thyroxine converts to T3 and reverse T3. Reverse T3 is the body's brake on too much T3 being converted and causing hyperthyroidism. Impaired DIO2 can impair conversion to T3 and the build up of unconverted T4 creates rT3. It can take up to 14 weeks on T3 only to clear a build up of T4 or rT3 but people with impaired D1O2 will usually do well then on a combination of T4+T3, the T3 overcoming the conversion issue and stimulating T4 to T3 conversion.

I was very unwell when I was switched to T4 but adding T3 improved brain fog and clarity of thought although it didn't touch on physical symptoms.

The brain is greedy for T3 which is why hypothyroidism can cause depression and sufficient T4 or T3 can relieve depression. The brain will take what it needs at the expense of the rest of the body. I tried doses of T3 between 60 and 120mcg without improvement until I cleared the build up of T4. When I resumed T4 I had palpitations and shortness of breath within hours but adding 20mcg T3 calmed the adverse effects.

I don't want to add to your concerns but impaired DIO2 can also reduce bone mineral density and it may be worth having periodic DEXA scans to monitor your BMD.

Thanks for the Psycheducation link. I'm still reading through and finding it very interesting.

1 like

Thanks again, very interesting info.

I was not aware of the potential use of T3 in clearing excess T4 from the body. Regarding my own situation, I stopped taking levothyroxine about 6 weeks ago but a recent blood test shows my TSH is still impaired by a slightly elevated T4.

I was planning on waiting for my blood levels to return to normal before beginning any trials with T3, but your post seems to infer I might be able to actually use the T3 to speed up this process manually. Have I understood this correctly?

Thanks again, all your advice has been invaluable.


Hugo, no, the fastest way to clear a build up of T4 is to take nothing, which isn't an option for most hypothyroid patients.

T3 doesn't clear a build up of T4, it provides an alternative thyroid hormone therapy for hypothyroid patients and T4 build up clears because T4 isn't being taken.

Do you know what your thyroid levels were prior to taking Levothyroxine and how they compare now?


I had blood tests done about 3 weeks ago, TSH was apparently way down (effectively nil) but FT4 and FT3 levels were "within range". I'm currently waiting for a copy of the results.

My doctor (a psychiatrist) wants to wait for my thyroid to recover before pursuing any other thyroid related medication, and took another blood sample late last week. I should get the results back in a few days.

On a side note, my doctor is in fact is entirely unconvinced my symptoms are related to thyroid malfunction, in spite of the positive DI02 test, and is keen to start a course of the antidepressant Venlafaxine as soon as possible. Having had many bad experiences on antidepressants I'm reluctant to do so before at least trying a course of T3, which my doctor is very unlikely to prescribe and hence why I'm now looking at sourcing it online.

The only thing delaying me now is the idea that I should wait for blood levels to first recover, although I'm now wondering if there's much point in this?


Hugo, It's a pity your psychiatrist having trialled T4 is unwilling to trial T3. If FT3 is at the top of range it will take very little T3 to send it over which in thyroid terms would be overmedication but I would guess your FT4 and FT3 were substantially over when you were on 400mcg T4. What were your FT4 and FT3 then?

I was quite happy taking Venlafaxine but when thyroid issues were being investigated an ECG showed an arrythmia, prolonged QT interval, and GP said Venlafaxine was contraindicated and switched me to Sertraline which was as good, certainly no worse. Both kept me stable without manic flares.


Sorry not to have made this clear - my current psychiatrist wasn't the one who originally prescribed levothyroxine; I stopped seeing him as I was unhappy with his desire to persists with T4 in spite of the negative side effects I was experiencing. At this time my FT3 and FT4 levels were way up, something like 15.1 and 81.0 respectively, and my main symptoms (brain fog and fatigue) were ever present.

Since then I have struggled to find a psychiatrist familiar with any thyroid related medication, let alone for T3.

Interesting your comments re Venlafaxine. It is certainly something I'd consider if T3 fails to have an effect.


Hugo, in thyroid land FT4 81 and FT3 15 would be seen as dangerously overmedicated or hyperthyroid and would have endocrinologists freaking in horror. I thought the psyched article advocated reducing dose when the patient felt overmedicated?

I felt dreadful with FT4 >34 and FT3 only slightly over range but I had problems with T4 only so it may have been the T4. I didn't have any adverse or hyper symptoms when I over medicated on T3 and was 50% over range although my hair started falling out. One of the good things about T3 is that if you do over medicate it's short half life means it will be out of your system 48-72 hours after the last dose, unlike T4 which has a half life of 7-8 days and can take much longer to completely clear your system. You should remember though that T4 or T3 are seen as adjuncts to refractive antidepressant treatment rather than stand alone depressive treatments.

Although I had no withdrawal symptoms from Venlafaxine you should be aware that some people can suffer quite extreme withdrawal. I daresay the same is true of most antidepressants.


From what I have read, DIO2 also converts rT3 to T2. Hence an unusual form of DIO2 might affect that process as well.



Sorry to hear you have been having a hard time.

I have put a question on the forum regarding my daughter taking a quite high dose of T3.

She has been unwell for six years, her G.P. saying she has CFS.

I am hypo. and her symptoms are very like mine but her thyroid levels were always "in range" (until last year TSH very top of range) still her G.P. would not treat her so she has decided to self treat.

She has increased the dose of T3 over the last 4 months to 100mcg. and just had a blood test and her level is 7.7 range 3.1 - 6.8 so obviously over range.

She has seen some really good improvements but has started to suffer insomnia and fatigue but this maybe because she is a little overdosed now.

Too little or too much can cause symptoms, so it is a case of adjusting the dose to feel well.

Hope this helps a little.

Best wishes browny


Thanks for the advice browny. Has your daughter's CFS gone or is she still experiencing these symptoms along with insomnia? And has she been prescribed T3 or are you buying this online somehwere? If the latter could you possibly PM me the link? Many thanks


I will P.M. you


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