Thyroid UK
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How much TSH fluctuation is normal?

Hi, I was wondering if anyone could possibly advise or share their experience... I am on 75mcg of levo and have been since September. In November my TSH was 0.75 (0.27-4.2) and I was feeling pretty much back to normal. I've just been restested this week (because I started taking a herbal supplement for PCOS 6 weeks ago) and TSH is 1.3. Would this be a significant difference or is that amount of fluctuation perfectly normal? I have been feeling a bit tired, but I have also had a busy few weeks so it's hard to tell why. I didn't feel good when TSH was 1.9 though, and the doc agreed then that we'd try and keep it below 1, but does 0.3 matter?! It's virtually impossible to get T4 tested (and T3 is totally impossible) so I haven't got much to go on. Any thoughts would be much appreciated, thank you.


4 Replies

I think we all have a number where we feel best but if other issues change, that optimal level could also change. My experience is that my TSH at 1.66 seems sufficient but if I go over 2.0 I can tell, so it looks like a rather small window. Unfortunately my FT4 and FT3 were barely in range so the TSH may not really coincide with the other measurements. But I have been at this for many years.


As Heloise states, we do eventually find a number we feel well at but the best way to know which dose suits, is one that makes you feel better. Some GP's adjust doses according to the TSH and that's not a very good idea unless you have taken far too much.

Your quite newly diagnosed and levothyroxine is usually gradually increased. If you feel unwell and TSH rising, then you most probably need an increase. Normally it is about 25mcg each time. When you feel worse, it's time for a new blood test. Always get copies of your thyroid gland blood tests, with ranges, for your own records and you can post if you have a query.

Do not take your medication on the morning of your test and have it as early as possible. Take it afterwards.


A decrease in thyroxine saw my TSH rise from 0.01 to 0.03 and it felt like a real improvement to me although I still felt overmedicated and rubbish.


Thank you very much for the replies


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