Thyroid UK
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Help interpreting bloods please! Taking T3, I thought TSH would go down if anything?


Can you please help me with my latest blood test results? I’ll give you the previous two sets first which were both before I started T3/liothyronine, then the most recent one which was taken 5 weeks after starting (I’m on 10mcg/day, didn’t take any the morning before the test):


TSH 1.23 (0.35 - 4.5)

Free T3 3.4 (3.9 - 6.8)

Free T4 15.2 (11 - 26)


TSH 1.65 (0.35 - 4.5)

Free T3 3.1 (3.9 - 6.8)

Free T4 15 (11 - 26)


TSH 2.33 (0.35 - 4.5)

Free T3 4.3 (3.9 - 6.8)

Free T4 12.4 (11 - 26)

I thought, perhaps incorrectly, if anything my TSH would go down if my T3 level increased? Or is it going up because my T4 has gone down? Why would the liothyronine make my T4 go down?

I was hoping that my endo would agree to increase my liothyronine when I see him next, perhaps adding an afternoon dose because at the moment I take 10mcg in the morning and the small benefit I feel has worn off by around lunchtime.

Does it seem likely he’ll be happy to do that based on these recent results?

As you can see from my results it’s a conversion issue that I have and I’ve got CFS/ME. No issue with thyroid antibodies shown on test results from Feb.

Many thanks for your help!

14 Replies

Maybe I should add that my most recent tests were taken at 9am (others were at least a couple of hours later) and I had eaten breakfast about an hour and half beforehand - in case that makes much of a difference?!


Certainly the difference in time would make some difference. The TSH is highest early in the morning, and drops throughout the day. It also drops slightly after eating. But I'm not sure before which test you ate breakfast.

How much levo are you taking? Because, in the first two tests, you're clearly under-medicated. Taking T3 does cause lower FT4 levels. One would expect that to happen. But the difference is so slight that it wouldn't cause the TSH to rise. But, then again, the rise in your TSH is so slight that it would more than likely be the timing of the blood draw that has made the difference. :)


Thanks for responding greygoose - I’m not taking any levo, I’m on T3 only.

Why does it lower FT4?

Do my results seem what you might expect then? And do you think it’s likely the endo would consider an increase in my liothyronine?


Well, given that 10 mcg T3 only is a totally inadequate dose, I would have expected worse! Why aren't you taking any levo?

If you're not taking any T4, and your thyroid isn't making much, your FT4 is obviously going to be low. But, in any case, when you're taking T3, your body doesn't need as much T4, so only hangs on to what it wants.

But, I don't really understand what's going on, here. Have you never taken any levo? Your endo just put you straight onto 10 mcg T3? That's a rather unorthodox approach, to say the least. But you really can't ask people to interpret your blood tests without giving all the details. I've just looked on your profile, and there are no details except to say that you're taking 10 mcg T3, none of the background, no explanations. The interpretation of blood tests depends on what you're taking. And, I assumed that you were taking T4+T3, which is the more conventional approach.

Expecting someone to survive on just 10 mcg T3 is pushing blind faith to its extremes. So, would you care to fill us in on what exactly is happening, please. What is your history? What is your diagnosis? How did all this come about? :)


Sorry for not giving enough info (partly brain fog, partly not realising it wasn’t sufficient as I explained it). I’ll give you some now and will update my profile soon too.

I have had pretty severe fatigue since the summer of 2016, along with other symptoms such as aches and pains, major brain fog/cognitive issues, stomach issues (largely cramps and constipation), food intolerances appearing out of nowhere (dairy, gluten, and more recently mustard), dry skin, acne, dizziness, and more than I can’t think of off the top of my head right now!

I was diagnosed with CFS/ME August 2017 but have been keen to keep exploring other possible causes or contributing factors. My TSH was in normal range when the GP tested it about May 2017 but having read that doesn’t give the full picture I ordered tests privately at the end of 2017 (first set of results above).

As the FT3 was below range I took my results to my GP - long story short he wasn’t helpful and I decided to see an endo privately.

I’ve been off work since the beginning of the year because my symptoms were worsening so much through trying to push myself to work. It was getting pretty scary, to the point where I would struggle to move my limbs when I woke up in the morning and I was really worried about how it was progressing.

I’m doing better now that I’m focussing on my health (largely because I’m not doing much every day) but my body’s tolerance to any physical, mental or emotional exertion is still very small and I’m trying to get the balance right between resting and building gently on doing things to try to increase my tolerance.

The private endo was happy with my FT4 being where it was in the range - hence no levo. He said the first two sets of results do not indicate that I’m hypo but that he was happy to try an unconventional approach in trialling T3/liothyronine only as he was keen to try and help improve my symptoms.

I took 5mcg once a day in the morning for a week, then went on to 10mcg. On the days that my fatigue isn’t as bad as it can be I do feel a small benefit from the 10mcg for a few hours. On days when then fatigue is worse, I don’t feel any benefit at all.

I hope that’s a more helpful summary - please let me know if Ive missed anything useful 😃

Do you think I need T4 too then?


I think you need more T3

The result should be more like 5.0 or 5.5


Thanks for replying reallyfedup, that’s good to know that it should be higher up the range.

I certainly feel like I could take more, fingers crossed the endo agrees when I see him in a couple of weeks.


Had it been me that first saw those results in December 2017, I would have wanted testing for Central hypo. Your TSH should have been higher than that with an under-range FT3. And, in February, both your Frees got lower. Although your TSH didn't get much higher. More tests should have been done. Because, if you do have Central hypo, caused by a pituitary problem, there could be other hormonal deficiencies as well as the TSH. You could have low ACTH, which would affect your adrenals. Which might go some way towards explaining the ME/CFS 'diagnosis'. The pituitary produces quite a few other hormones than the TSH.

And, whilst it sounds like a good theory to just add in a bit of T3, just to top it up, like, sort of thing. It rarely works like that. Adding in either T3 or T4 is not topping up, it is going to affect the working of your thyroid altogether. Plus, the low TSH is not just affecting the production of hormones by your thyroid, it is also affecting your conversion. So, it's doubtful if you will be able to stop at just 10 mcg. But, it doesn't sound as if your private endo understands enough about thyroid to know that.

If it were me, I would want to go back to the beginning, and get tested for Central hypo. Below are a couple of links that you might find helpful.

You can just copy what you've written above and paste it into your profile. No need to start from scratch, the above will do nicely. :)


Thanks again!! I have had some more tests that I completely forgot to mention (sorry!) but your mentioning ACTH has reminded me!

The private endo had a short synacthen test done which apparently showed a normal reaction:

950 before given injection 333 nmol/L

1030 584 nmol/L

1100 705 mol/L

I've been seeing a nutritional therapist who suggested I do a saliva test and that showed the opposite of what we were expecting - that I actually had high cortisol at all four points during the day:

Sample 1 10.46 (2.68 - 9.30)

Sample 2 4.41 (0.75 - 2.93)

Sample 3 2.87 (0.36 - 1.88)

Sample 4 1.19 (<=0.94)

DHEA Sample 1 (am) 0.59 (0.25 - 2.22)

DHEA : Cortisol Ratio 0.06 (0.05 - 0.32)

Private endo said it was dangerous to try to adjust high cortisol levels because of the potential knock on effect on other processes/hormones. It's strange because I really don't feel like there's I've got high cortisol.

Endo did also test the following in February:

FSH 4 iu/L (1 - 11)

LH 2.5 iu/L (1 - 12)

Prolactin 451 mu/L (102 - 496)

Thank you for posting those links - having read them, I'm not really sure what other tests I would need to investigate central hypothyroidism, would I need anything other than the additional ones I've listed above?

Sorry for all the questions. I am trying to look for the answers but my brain fog symptoms make it very difficult, I do really appreciate your help.


The private endo had a short synacthen test done which apparently showed a normal reaction:

The short synacthen test is a test to see if you have Addison's, it's an adrenal test, but is not going to tell you much about your pituitary.

I don't think your cortisol results are really high enough to make themselves felt as high cortisol. But I'm not convinced your endo is right about reducing cortisol. Does it stop you sleeping?

Your FSH and LH are very low, so I think it's a theory worth pursuing. You could also have a serum ACTH test - not the stress test - and test GH.


I don’t really have trouble sleeping. For the most part I fall asleep easily and then sleep soundly all night, but wake up feeling like I’ve been awake most of the night.

I thought all the samples were outside the top of range so we’re therefore a bit on the high side. I’m wondering whether there’s any value in having that done again in a month or so, to see if it’s still higher than normal or if that was just that snapshot in time.

Thank you so much for the suggestions greygoose, I will bring it all up with the endo when I see him in a couple of weeks.


They are slightly outside the range. But not enough to cause alarm. And, if it doesn't affect your sleep, then fine!

I was going to suggest that you wait a while and then get retested - in more than a month, I would have thought - and continue to keep an eye on it. It might sort itself out when you get other things sorted. Or, it might continue getting higher. You need to know. :)


Great, thank you greygoose!!😃


You're welcome. :)

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