Thyroid UK
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Low TSH, Normal T4 but doctors wants to reduce dose by 1/3


I've had an under active thyroid for almost 15 years and my levels have generally been stable. For the past few months I've been getting hypo symptoms more than usual- fatigue, depression, no appetite, sleeping 12 hours at night and wanting more!

I request a blood test and my results have come in with a low tsh (0.03) and normal t4 (5.5) but my doctor wants to reduce my dose from 150mcg to 100mcg! I don't understand why a low TSH is a problem with T4 in range- and specially when I'm feeling hypo at the moment anyway!

Should I push for full thyroid blood tests, I don't think my T3 level has been checked since I was under the care of paediatrics.

Thanks for much for reading my post.

4 Replies


Levothyroxine dose is usually adjusted in 25mcg increments at six week increments. 50mcg is rather drastic. I've been arguing with my endo that suppressed TSH doesn't indicate over medication when FT4 and FT3 are within range. Endo insists that I am increasing my risk of heart and bone problems by having TSH <0.05 but I've refused to reduce dose since 3 reductions last year failed to budge my TSH up.

Primary care rarely tests FT3 but you can order private thyroid tests via

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That's what I thought- she wants third of my levothyroxine cut when I'm experiencing symptoms suggesting otherwise and there's no discussion of anything further to look into.

Are the online private tests reliable? I can see one that's a finger prick for t3 for £29 which looks good (I'm on a really low income due to being fatigued all the time!!).

I'm trying to look into whether a low TSH causes problems but I can't find anything. I'm sure I've read before that if you're getting thyroxine replacement drugs your TSH SHOULD be really low because that's the whole point!

Thanks for taking the time to reply I really appreciate it.



These tests are accurate but it might be better to find out whether the result will make any difference to your GP before shelling out. Perhaps you could negotiate a dose reduction of 25mcg instead of 50mcg or ask for a second opinion.

If you Google "Suppressed TSH" or "Suppressed TSH+atrial fibrillation+osteoporosis" you'll get hits. It's debatable how low TSH should be. Most research states that suppressing TSH <0.1 increases the risks of developing atrial fibrillation and osteoporosis.

I've always argued that a lot of that research is extrapolated from hyperthyroid research where TSH is suppressed AND FT4 &/or FT3 is over range. My endo is not happy with my TSH <0.01 and would prefer to see it around 0.05 even though FT4 and FT3 are within range.

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I wish doctors would be better trained, Let's revert back to when patients were sensiitivey and sensibly treated and given thyroid hormones until they had no awful symptoms. Just like the 'old-fashioned' way and I don't think they developed heart attacks, nervous breakdowns, lost work or anything else. Doctors used to give them a trial of thyroid hormones according to clinical symptoms.

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