Thyroid UK
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T3 still low despite high doses

Hello Everyone. I hope that this finds you all well and navigating this frustrating journey as well as you are able. I haven't posted in a while but now have some questions. Some of you may remember my case. I am on high doses of T3 for suspected resistance to thyroid hormone. I am on 270-360 mcg of T3 however my latest results show the following.

TSH <0.008 (.35-5.5)

Free T4 0.23 (0.71-1.85)

Free T3 1.3 (2.3-4.2)

The suppressed TSH and T4 make sense but NOT the T3. What is going on? Any thoughts on this at all?

11 Replies

It strikes me there are two logical possibilities here.

The first - that maybe some of the T3 you're taking isn't actually T3, or doesn't contain as much T3 as it says it does. Have you purchased it from a reputable source?

And second, that you just aren't absorbing the stuff properly - something's working, because your TSH is suppressed - but clearly not enough. I don't know what to advise though, if I'm honest. I suspect you may have more than one autoimmune problem.


Thanks Jazzw.

If absorption was an issue then I would think that the TSH and T4 would not be suppressed. I have used two different pharmacies however the last test was with the new pharmacy so I do want to go back to the old one and retest. The pharmacies are compounding pharmacies. 45 mcg caps each. Also, just to clarify, I do not have any detectable antibodies (TPO or TG) nor any other AI disease. I am however wondering at this point about T3 antibodies and how this would show up


Are you anaemic?

Are you taking T3 on an empty stomach at least an hour before eating? Also are you taking any other medication that may give you absorption problems? I'm thinking low stomach acid? Have you tried drinking cider vinegar? Or taking vitamin C with your T3 to get it absorbed better?

To be honest I'm clutching at straws here, you usually have T3 in your blood even if not a lot is getting in to your cells?

Have you had any other tests like a 24 hour urine test to see more accurately what is going on?


Hi Helcaster.

Not anemic, no. Ferretin last check was 60 or so. No other meds though except LDN. I do take ACV on occasion but haven't taken C with T3. I take T3 right before I go to bed along with the LDN.

No 24 HR urine test has been done. Honestly there are not many docs that want to work with me and the one that is is getting annoyed and keeps reducing my dose (and this is the end result perhaps??)


Hi again, just an observation Suzanneai , ferritin should be at least 90. Iron is needed to carry T3 to the cells. But that doesn't explain why your blood tests show low T3! Why would your doctor reduce your dose?

The other thing that may cause problems is milk protein, if you eat or drink something milky it should be at least a couple of hours away from taking your T3.

You're usually advised to take other drugs 4 hours away from T3 Levothyroxine etc. I have to take other prescription drugs for a different health problem, so I take those in the evening now.

You can do a 24 hour urine test privately. I know there have people on this site that have. Genova was one of the labs offering it.


Yes, I agree. The ferretin would explain resistance more that the low T3 only. The doc wants to reduce as she is worried about not being able to justify this amount of T3 should there be an issue with it. I went from 360-135 over night and it has been 3 weeks and I feel like death to be honest. I do eat a bit of cheese in the eve some nights but not a lot. thanks, I will be more mindful of this. also, does the 24 hour look at T3 excretion?? how expensive.


Hi Suzannai, I take 125mcg of T3 and I'm not doing well at all. I've gained a lot of weight, still have really dry skin, temps that are too low, exhaustion. I could easily take more T3, I just don't feel anything happening to be honest. I know I have low cortisol so I'm taking 20mg of hydrocortisone and still no better. I'm feeling lost too!

My last resort is to wean off a drug I need for interstitial cystitis as it gives me low stomach acid. I had my first day without it today! I've trebled the dose of the other drug I take for it, but not sure if it's going to keep the pain away.

I wanted the 24 hour urine test but Genova wouldn't do it because I have was taking cimetidine, so I'll just wait for it to leave my system and get that test. I can't remember exactly the cost, at least £100 I'm sure. The adrenal stress test was just over £80. It's all money!! It's supposed to be more accurate as to how much T3 etc is getting into your cells. Worth a look are you in the US? Maybe you can access a private lab, check out the test and costs?

One last thing I thought of today, is do you drink a lot of coffee or tea? This messes up absorption of thyroid meds too.


I agree that I don't feel better on more T3 than the 360 mcg but the 135 is too low with out question. Cant get an answer as to why when I take such a high dose that the T3 is not getting in. Something has happened since last Aug when my T3 was well over range. but I don't know and it seems no doctors do either. I am still thinking of the stress componenet here as for me it all started with stress when cortisol was high on both urine and blood but when I tested 4 pt last year it was all normal although not optimal. I am so tired of meds and pills and supplements abut would take anything if it helped but the trial and error to be honest sucks. I have also read that vitamin A def can lead to thyroid resistance and I also take that and no big difference. I suppose what I would expect if a med/supplemenet was working would be hyper symptoms but nothing has induced that. I also came across the link to potassium and how it is needed to help T3 but still does not explain why my levels are so low. I take it all at once and people say it should be taken throughout the day, however they may be right the point still remains as to why that high dose at once doesn't make me hyper or even better. god knows. sorry for the rant. I will look into the urine test. Is it a T3 test? I will see what genova has and if doc will order. thanks again.


Hi Suzannai, Genova is in the US too, the urine test measures T4 and T3 that has been exposed to the cells. I know often these results are very different to the blood tests. I've been keen to do this for some time. There's one involving stress hormones too. There's quite a list of endocrine tests, worth having a look.

I'm like you, just can't seem to crack it, nearly 4 years of trying everything possible and still far from well.

I've had a rough, tearful day so far, I decided to take my temperature. After 75mcg of T3 and 25mg of hydrocortisone it was 36.3, a few days ago it was much higher. The lower my temperature the more unwell I feel. Other people feel great on what I'm doing, it's so frustrating! I'm seriously thinking of going back to Armour, at least my weight came down.

Like you no matter how much i've taken I have never felt hyper. At one point I was taking 3 grains of Armour and 150mcg of T3 and was still very cold etc etc, but on that combination I did feel like my weight was more under control.

Rant away! I feel like it too! Xx


Sandy12. Thyroid binding globulin? It would be a good idea to test both; I do agree with that but am wanting more info before I spend another 200 dollars.


with regards to thyroid resistance...does potassium make any sense.

The potassium level is associated with sensitivity of the tissues to thyroid hormone. Low hair potassium is associated with reduced sensitivity of the mitochondrial receptors to thyroid hormone. Even if circulating hormone levels are normal and hormones can be absorbed into the cells, when tissue potassium is low they may not be utilized, resulting in a low thyroid effect. This commonly contributes to thyroid problems in slow metabolizers. Potassium supplements rarely help because the problem is a loss of potassium due to kidney dysfunction and electrical imbalances at the cellular level.


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