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Thyroid UK
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Suppressed TSH <0.01

I recently had a fasting blood (no meds for 24 hours) late morning (no early appts with this endo!) and my TSH is marked at low.

My ft4 is15.7 (range 11 to 26) and ft3 is 4.7 (range 3.9 to 6.8). I know t3 can suppress TSH, I'm just surprised my ft3 isn't higher. I am generally much better on t3, which i tolerate ok now i split it into 2 doses. I just wish i had more stamina.

I stopped supplementing b12 for a few months and it went from over a thousand to 457 so I'll start that again.

I'm on 50mg levo and 15mg t3.

Has anyone managed to get their ft3 levels up higher with a suppressed TSH? I'm supplementing and other vitamins and iron are in a healthy state.

4 Replies

Your combined dose is quite low, equal to around 100mcg of levo. Your FT4 and FT3 should be in the upper part of the range. I think you need an increase in levothyroxine.

The TSH is only a guide, usually used to diagnose hypothyroidism when it reaches above the range - in the UK it is when it reaches 10 (far too high).

TSH is from the pituitary gland and rises when thyroid gland is struggling. I go by the following doctor's advice.


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If you left 24 hours between your last dose of T3 and the blood draw, it was too long, so you have a false low, there. It's recommended to leave between 8 and 12 hours for T3. 24 hours for T4.

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Oh. That's a revelation to me! At the time, i was taking all my meds around 7 in the morning so that blood test was actually 28 hours since the last meds.

I'll do as you advise next time as that will help with a more accurate result. I'm not feeling too bad really so was surprised ft3 was thst low!

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My FT3 is generally at the bottom of the range. I used to want to increase my T3 but actually I've lost weight by radically changing what I eat and now I feel better but still read at the bottom of the range.

That is a very low TSH (I sound like my endo!) particularly as it was so long after the meds. Stamina can take a long time to come back mine is returning after almost three years on T3 only (and a lot of dietary changes).

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