Thyroid UK
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Long term side effects T3

I have been taking 100mg thyroxine and 2 x20mgm of T3 daily for the past 9 years I have extremely well on this dose but the test always comes back to high my GP now has retired and my new GP is sticking to the paper test and not my vital signs she says thats it dangerous long term to continue its only been two weeks since she reduced it and I feel awful already Help what can I do

26 Replies

You'll have to source T3 from elsewhere. GPs know very little about metabolism. Dr Lowe took T3 at 150mcg daily since he was a teenager till he died of an accident. Some links with excerpts:

Dr. Lowe: I respectfully disagree with your endocrinologist. Studies indicate that T4 is of no use to anyone except, figuratively, as a storage unit for the metabolically-active thyroid hormones T3, T2, and possibly T1. When T4 ends its long ride through the circulating blood, it enters cells. There, enzymes convert it to T3, and, after a while, other enzymes convert T3 to T2. The T2 becomes T1, and eventually T1 becomes T0 (T-zero). T0 is just the amino acid backbone(called "tyrosine") with no iodine atoms attached. Because it has no attached iodine atoms, T0 is no more a hormone than is T4.

Rather than being a hormone, T4 is a “prohormone.” That means that enzymes have to convert T4 to T3 before T4 benefits us. T4 is no more a hormone than beans in an unopened can are a food. For all practical purposes, canned beans become food only when a can opener frees them so you can eat them. Hence, T4, like canned beans, only potentially benefits us, but actually does so only after being freed from its metabolically unusable form.

Your endocrinologist may say that T4 is a gentler way to get T3 into your body. This to me, however, is a specious argument. When taken properly, T3 can effect one as gently as T3 derived from T4. and.......

Most endocrinologists subscribe to the practice guidelines of the American Association of Clinical Endocrinologists. When a patient such as you sees one of these endocrinologists, he’s likely to take her off T3 and switch her to T4-replacement. As many patients have told us, when an endocrinologist switched them to T4-replacement, they became ill and dysfunctional again. These reports are consistent with studies that show the ineffectiveness and potential harm of T4-replacement. The studies show that T4-replacement leaves many patients suffering chronically from hypothyroid symptoms[1][2][3][4][5][6][7] and gaining weight they can't lose through dieting and exercise.[8] The patients are also likely to use more drugs and develop one or more of several potentially-fatal diseases.[9]

Potential harm from T4-replacement has thus been scientifically documented. In view of the risks, you must consider for yourself whether you'll permit your therapy to be changed from Cytomel to T4-replacement. If you decide not to permit it, you can seek out an alternative doctor who understands how ineffective and harmful T4-replacement is for many patients. Alternative doctors are generally more cooperative than conventional doctors, and most of them take the time to learn the cause of troubling symptoms. Because of this, you should be able to find one who'll help you ferret out and correct what's causing your occasional symptoms of overstimulation. and......

Conventional endocrinologists' lack of knowledge about T3 results from conduct that is clearly unscientific—that is, overall, they accepted without question mandates passed down to them by old guard thyroid specialists, much as loyal military personnel obediently and unquestioningly comply with orders from higher command. The particular mandate of conventional thyroid specialists I refer to here is this: "The only thyroid hormone preparation a doctor should ever prescribe is T4 (thyroxine)."

To the discredit of both conventional endocrinologists and the thyroid specialists whose edicts the obey, this mandate is not scientifically based. Instead, it’s based on a powerful marketing campaign of a major pharmaceutical company. This marketing campaign, not science, is precisely why most doctors robotically write "Synthroid" on their prescription pads when they learn that a patient is hypothyroid. Conventional doctors, including endocrinologists, have allowed their minds to be utterly subjugated by this marketing campaign. As a result, they’ve deprived themselves of clinical experience with any thyroid preparation other than T4.

So, the wariness of conventional doctors, including endocrinologists, about the use of T3 is born of ignorance. Thus, as a whole, they are the least qualified doctors from whom to seek expert advice about T3. In the past several years, many unconventional doctors have acquired extensive experience with the use of T3. These doctors include many family physicians, physiatrists, psychiatrists, nutritional and holistic doctors, and naturopathic physicians. For expert advice about T3, it seems prudent to bypass endocrinologists and to look to these more knowledgeable and experienced doctors.

Maybe she would welcome a copy. :)


"Rather than being a hormone, T4 is a “prohormone.” That means that enzymes have to convert T4 to T3 before T4 benefits us."

The above statement is not true. T4 has "non-genomic" effects. This means it has an effect as T4, before conversion. Not all action is at the nuclear receptor; some is at the membrane or in the cytoplasm. joe.endocrinology-journals....


Thank you x


Thank you so much I will stick out for the T3 and if not will get it elsewhere x


Welcome to the forum, Tecnogran.

Can you post your recent thyroid results with the lab ref ranges (the figures in brackets after your results) as it helps members to advise.

There are concerns that long term suppressed TSH &/or high FT3 may cause atrial fibrillation and osteoporosis. When my FT3 was over range in the autumn my endo suggested reducing my T3 "because we don't really know what the long term effects are". In general, FT3 should remain within range but there are patients who feel unwell unless it is higher. Some members have agreed to have ECGs and DEXA scans to monitor bone density in order to allay GP's concerns.

Unless you can persuade your GP, or a different GP at your practise, to prescribe the dose of T3 on which you feel well, you may have to consider buying your own T3 and self medicating.


Thank you I will try to post my results here - The endo did say he would comply with my wishes after I tried the reduction should I wish to go back up again but he did say I would have to face the consequences which did scare me a tittle ... BUT they don't know the long term effects and if I have to live like a zombie I would prefer to have the higher dose ... as now I am slipping back to where I used to be and I don't like it x


Technogran, It's a balancing act, enough thyroid meds now to enjoy some quality of life means accepting there may be future adverse health implications. You have to weigh up the pros and cons to make your decision. To my mind, feeling suboptimal now may reduce the risks but doesn't eliminate them.


Totally Agree I am 65 in March felt better than i have done since I was 36 years old and started with the ME/CFS I have lost 30 years of my life already I don't want to loose any more I am prepared to take the risk live now pay later <3


Technogran, exactly, we could be run over by a bus tomorrow so might as well feel good today :-D


Dr Lowe's CV

This is an excerpt:

Dr. Lowe: First, let me clarify an important point: Our treatment protocol does not consist solely of patients using T3. Only two groups of our patients use T3. One group is patients who appear to have thyroid hormone resistance. The other group is hypothyroid patients who fail to benefit from desiccated thyroid. Our other patients use desiccated thyroid as part of their metabolic rehabilitation regimen. (We don’t, of course, waste time any more trying T4 alone; it’s too seldom of any use.)

Now, to address your rheumatologist’s assertion that T3 is dangerous, and his implication that amitriptyline is not. I think the best way to reply to him is to quote publications that are available to him. In the USA, when patients get their prescriptions filled for T3 (usually the brand Cytomel), the pharmacist usually gives them a leaflet on the product. The leaflet contains the following statement:

"NO COMMON SIDE EFFECTS HAVE BEEN REPORTED with the proper use of this medicine." (Medi-Span, Inc.: Database Version 97.2. Data © 1997.)

This statement makes a fact perfectly clear: When used sensibly, T3 is extraordinarily safe among prescribed drugs. When I say extraordinarily safe, I’m comparing T3 with drugs such as the amitriptyline which your rheumatologist prescribes for you. Below is a list of potential harmful effects of amitriptyline. This list comes from the Physician’s Desk Reference, 53rd edition, Medical Economics Company, Inc., Montvale, 1999, page 3418.


I don't know what he means by "old hat." As medications go, T4 has been around a lot longer, and desiccated thyroid even longer. As for stability, T3 is certainly as stable as T4 and desiccated thyroid. Synthroid (the most prescribed form of thyroid hormone) is not more stable than Cytomel. At this time, Synthroid users are being reimbursed millions of dollars, partly because of significant variability in the potency of the product.

And ". . . caused strokes"? If anything, the use of T3 may help prevent strokes. I scanned MEDLINE for studies on "T3" and "strokes" published between 1966 and 1997. These key words were mentioned in 43 publications. Most publications reported the beneficial effects of T3 on cardiovascular function. The word "stroke" was most often used in regard to the "stroke work in cardiac contractility" (a physiological description)—not in the sense of cerebrovascular accidents (strokes). I'll mention just a few representative publications. These suggest that it is urgent for the physician you mention—for his patients' welfare—to quickly update his knowledge.

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Thyroid Function test taken October says :T3 Raised at 9.8 TSH suppressed at 0.01 ... I am taking 1x100gm T4 & 2x20mg T3 daily he has reduced the T£ by 10 mg I feel exhausted again


Technogran, Did you take your thyroid meds before the blood test? FT3 is very high. The highest FT3 range I've seen is around 7.0 so you are considerably over and this may increase the risks of OP and AF. What dose has your doctor reduced you to and how are you feeling on it?


I took my meds as normal He has reduced it to 1 T3 x 20 on a morning and 10 mg T3 evening ... I feel awful exhausted pains all over that was after two weeks brain fog loss of memory I have been taking my 2 x T3 20 mg since 2006 my levels come back hi all the time but the last time I reduced it I was so ill ... I have gone back to my original dose a few days ago I see the endo in March ... I have no problems with my heart OH I felt depressed again and constpated which I cant risk due to the Diverticulitis which has been fine for the time Ive been on the higher dose


Technogran, if you took meds prior to your blood test you'll have a false high T3 reading. Leave 24 hours for T3 and 12 hours for T3 before a blood draw. I think your FT3 will probably still be over range though.


Thyroid Function test taken October says :T3 Raised at 9.8 TSH suppressed at 0.01 ... I am taking 1x100gm T4 & 2x20mg T3 daily he has reduced the T£ by 10 mg I feel exhausted again - sorry if duplicating not sure what Im doing yet lol x


Technogran, I was surprised at how much my FT3 fell when I reduced T3 by 10mcg. I haven't felt worse for the decrease though and my hair stopped shedding and nails stopped splitting.

Are your ferritin, vitamin D, B12 and folate good? Low levels can cause musculoskeletal pain, fatigue and low mood.

I'm not suggesting it is coincidental that your T3 was reduced and you feel exhausted. FT3 9.8 was very high, some people do require FT3 over range to feel well. When is your next thyroid blood test?


The Endo was very nice and I am sure he is trying to help me ... He tested for all sorts and wants to try to get to the bottom of what is causing my ME/CFS too the thing is I was feeling so well until my GP retired and the new one has sparked all this off


Technogran, any chance you can have a thyroid test to see what your levels are now? If your GP won't do it you can order private thyroid tests through Blue Horizon and Genova via


Dr Lowe was an Adviser to Thyroiduk before he died two years ago. He had extensive knowledge and said T3 is not dangerous or causes us problems. He wrote a book called the Metabolic Treatment of Fibromyalgia and on Amazon it is over £1,000

If someone has thyroid hormone resistance, T3 is the only thyroid hormone which might make them well.

an excerpt

Dr. Lowe: The improvements you describe are typical of what we hear from patients using high-enough doses of Cytomel. Because of your improvements, and because your symptoms of possible overstimulation are occasional, taking you completely off Cytomel seems to me radically improper. This is Dr Lowe's CV plus biography

For someone taking 100 mcg of T3, we expect your pattern of lab results—a low TSH and high T3. However, your TSH and T3 levels are irrelevant to whether you're overstimulated or not. Two studies we just completed confirm other researchers findings: these tests are not reliable gauges of a patient's metabolic status. Many patients taking T3 have TSH and T3 levels like yours but still have severely low metabolic rates. Their metabolic rates become normal only when they increase their dosages further. Their metabolic rates become normal and they have no detectable overstimulation.

In some cases such as yours, the patient's Cytomel dose may need to be reduced. But symptoms such as occasional heart pounding and anxiety are usually not due to a patient's Cytomel dose. I say this because when Cytomel is solely responsible, symptoms of overstimulation are consistent, not occasional.


From what I have read in a medical paper, the risks of osteoporosis and atrial fibrillation are associated with low TSH.

However, the paper did not include any reference to the test subject's FT3 and FT4 levels or hormone replacement medication.

Has anyone seen anything that specifically links these risks with a specific intake of T3 or T4 medication, or levels of FT3 or FT4?


If you're interested in osteoporosis, there's some references here: Bones need both T4 and T3, and either an excess or deficiency will contribute to osteoporosis, not TSH.

The same applies to the heart, with heart health greatly affected by thyroid levels, not TSH.


Exactly. This artical supports the arguement that the risks are associated with serum hormone levels and not the levels of T4 and T3 medication, or any specific TSH result.

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This an excerpt from a paper:

So, as the right dose of thyroid hormone for you is the one at which you feel your health is optimum, and that dose can vary according to how active you are or how warm it is, it is not possible, surely, to specify a precise dose of thyroid hormone exactly meeting your needs for evermore.

I don't think Endocrinologists are as knowledgeable as scientists about the thyroid gland. Patients on high doses of T3 don't appear to develop additional problems as it makes them well. Excerpt:

This observation suggests that dosages

higher than those dictated by the replacement concept

more effectively relieve patients’ hypothyroid symp-

toms. Other research has shown that patients report

feeling better with TSH-suppressive dosages of thy-

roid hormone. Moreover, psychiatrists report

that dosages of T3 higher than replacement dosages

augment the depression-relieving effects of antide-

pressants. In addition, in a study of patients made hypothyroid by therapeutic destruction of the thyroid gland, some used TSH-suppressive dosages of thyroid hormone and others used T4 -replacement. Those on TSH-suppressive dosages did not gain excess weight; those on T 4 replacement did. The researchers concluded that T4 replacement was the

cause of the excess weight gain. These published

reports are consistent with thousands of cases in

which hypothyroid patients recovered from their

symptoms and other health problems with TSH-sup-

pressive dosages of thyroid hormone after T4-replace-

ment failed to help them.


Now that sound like a very sensible idea to me Thanks x


Is it your TSH result your GP is talking about? TSH is suppressed when taking T3, as T3 is the active hormone, therefore not in the feedback loop.


Muffy I am not sure I don't really understand all these tests, all I know is I have felt quite well since 2006 when I was put on the T3 up until then I had to spend most afternoons in bed in pain exhausted tired depressed ... the levels have come back too high every years but my GP was happy to go by how I felt and continue the problem has occurred becasue she retired ... I have spent all my savings over the years going from one quack to another trying to cure my ME/CFS the thing that has helped me more was the level of T3 I was taking ...


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