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Thyroid UK
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Advice on Levothyroxine

Hi. I am wondering if anyone can give me some advice please? I have been on Levothyroxine for about a year, after a long struggle to get diagnosed. I was started on 25mcg, then after 3 months the odes was increased to 50mcg and then up to 75mcg. During this time my TSH has steadily reduced but T4 was staying at around 12 (within a range of 12-24). 3 months after being increased to 75mcg (when I was starting to feel almost normal!) I had another blood test. TSH was 0.04 and T4 had risen to 15.8. However my doctor said the TSH was too low and reduced my dose back to 50mcg. I am now feeling very tired again, my hair is falling out in clumps and my mood is very low. I am not sure what to do as I have read that T4 should be near the top of the range and it had only just started to rise up, but is TSH 0.04 too low? By the way, I also have positive antibodies (Hashimotos) Thanks in advance

3 Replies

The TSH is irrelevant when you are on thyroid hormone replacement. Your doctor is ignorant, and I don't know what you can do about that! They think that a low TSH mean you've 'gone hyper' - a physical impossibility, but still... They do not realise that it is an over-range FT3 that constitutes a hyperthyroid state, the low TSH is just a consequence, not the main factor. It really doesn't matter how low the TSH goes as long as the FT3 is in range. But, as they never even test the FT3, how would they know!!!

Well, your TSH will rise again, now that you are on the lower dose, because your FT4 will drop (and, presumably, your FT3). So, he will have to put the dose up again (hopefully). But, the next time he wants to lower it - because his type never learn! - just say that you refuse to lower your dose until you've seen the FT3, because that is the most important number, not the TSH. If you make enough of a stink, he'll probably give in (perhaps I shouldn't say that! lol). But, if you say nothing, he will take that as agreement and lower your dose without a second thought. Remember, he is there to advise you, not to dictate to you. :)


Thank you for the reply greygoose. Am I right in thinking that T4 should be at the higher end of the range preferably? In which case 15.8 is still not that high. Unfortunately, I had to change practice to even get a diagnosis and, as this doctor had been good to me so far (in recognising my condition and treating it - which i suppose I should be grateful for lol), I didn't want to rock the boat. I took the drop in dose just to say I had tried it but it wasn't working for me. And it's not. As far as I'm aware I have only had my T3 tested once before I started on Levo and that was through a private Blue Horizon test; at that time it was 4.44 within a range of 3.1 - 6.8 but having been on medication for a year this is now obviously irrelevant.


That is a very wide range for the FT4! Even so, you are right that it should be in the top third of the range - or, wherever makes you feel ok.

It would be a good idea to get your FT3 tested again - at the same time as the FT4 - to see how well you're converting. If you aren't converting well, and your doctor insists on dosing by the TSH, then you will never get well.

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