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Thyroid UK
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Low TSH low T3/T4 please help !

Hi , my thyroid test results :

T4 : 15.8

TSH: 0.01

T3 : 3.5.

I'm on 100mg Levo but because my tsh is low my gp wants me to lower my dose to 75mg but im scared that would make me hypo again as my T4 and T3 already low , im also scared to stay on 100mg cause im not having my period for 4 months now , I really don't want to gain weight ( already gained 5 pounds last 2-3 months) what can I do ? Thanks

17 Replies

234556 It would be useful if you put the reference ranges in for your test results, the numbers on their own don't mean much as ranges vary from lab to lab. However, it's obvious your TSH is suppressed which is what your GP is freaking out about.

The aim of a treated hypo patient generally is for TSH to be 1 or below or wherever it is needed for FT4 and FT3 to be in the upper part of their respective reference ranges.

Dr Toft, leading endocrinologist and past president of the British Thyroid Association, states in Pulse Online Magazine:

"The appropriate dose of levothyroxine is that which restores euthyroidism and serum TSH to the lower part of the reference range - 0.2-0.5mU/l.

In this case, free thyroxine is likely to be in the upper part of its reference range or even slightly elevated – 18-22pmol/l. Most patients will feel well in that circumstance.

But some need a higher dose of levothyroxine to suppress serum TSH and then the serum-free T4 concentration will be elevated at around 24-28pmol/l.

This 'exogenous subclinical hyperthyroidism' is not dangerous as long as serum T3 is unequivocally normal – that is, serum total around T3 1.7nmol/l (reference range 1.0-2.2nmol/l)."

You can email louise.roberts@thyroiduk.org.uk for a copy of the article to show your GP.

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Thank you so much for replying, I will email louise roberts, my gp however doesn't care so much about it I think cause when I told him that I'm scared to gain weight if I lower my dose he just said then keep it 100mg and he said peroid is not important if I'm not trying for a baby he just said take 75 and let's test after 5 weeks what if i get hypo in 5 weeks then he will up my dose again and what's the point ? I'm so confused, thank you so much for replying again , I hope louise will help me.


234556 What makes you think that your lack of periods is anything to do with your thyroid? Has it been looked into? I've been hypo and treated for 43 years, many dose changes along the way, and have had FT4 and FT3 so low I turned into a zombie, but I never missed any periods.

Louise can send you the article, she is PA to Lyn Mynott who started Thyroid UK. Have a look around their main website


It might be an idea to ask for vitamins and minerals to be tested, many of us are low in these and need to supplement for our thyroid hormone to work properly. If your GP won't do them you can get them done privately with a fingerprick test:

Vit D





Oh also I dont really understand much but it's written like this

Serum free T4 (pmol/L) 15.8

Serum free TSH ( mix/L) 0.01(-)

Serum free triiodothyronine level (pool/L) 3.5


Are there any ranges after the numbers, eg

TSH 0.01 (0.2-4.2)

FT4 15.8 (12-22)


No :( this is all written nothing else, am I still hypo . I think it's my tsh levels cause 4-5 months ago I missed my peroid for 2 months and my doc lowered my dose to 75 that time and my tsh was 0.33 that time and I had my period just in weeks I took 75 mg for 3 weeks and by mistake I took 50mg for a month in that months all the hypo symtoms were back with monster appetite which I never had before so I asked my doctor and he upped the dose 100mg I still have the constant feeling of hunger plus no peroid , do you think I should lower my dose to 75? Oh also all my vitamin levels were checked 4 month ago just my vitamin d was low and I'm taking the supplement doc gave me , thank you so so much for replying


Can you post your results for vitamins and minerals. Just because they're in range doesn't mean they're optimal, which is what we need. Your GP will say they are fine even if they're just one point above the bottom of the range and optimal may be at the very top of the range.

Also, what was your Vit D level and what has your GP prescribed?

There are important co-factors needed when taking D3 which your GP won't know about because they're not trained in nutrition.

I can't say if you are 'still hypo' without knowing the ranges for FT4 and FT3. My guess is that your FT3 is low in range, and that your FT4 is either low or mid-range, which would mean that you are undermedicated and would still get symptoms of hypothyroidism.

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I actually don't have my vitamins as a result as it wasn't gp it was a privately doc in my country and he gave me a oil based vitamin d to take every 10 days for 3 months he also gave me b12 supplement that I also took and still taking even that time I couldn't understand how my vitamin d is low as my diet is very healthy lots of fish lots meat I don't remember as number but I remember he said vitamin d levels were really low , I finished the supplement he gave now since last month I'm taking cod liver oil from holland and Barrett once a day , also q10 , vitamin c and green tea extract and vitamin b complex. Hope I'm not doing something wrong


It's not possible to say if you're taking the right supplements at the right doses unless you have results, with ranges, plus tell us exactly what dose of each Supplement you're taking.


Vit D is also a tricky one as if you are low you. Red a booster dose to get it up then a maintenance dose for life. Some doctors only give you the maintenance dose which won't help you so that's why we need to know the results and what you have been told it do as you may not have been given the right advice.


your GP is wrong to worry about TSH

its clear from your very low t3 test results that you are not correctly converting the levo t4 into the t3 that every cell needs to function

usually this is because





are below halfway in their ranges thats what your gp should focus on sorting out

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Thank you replying, after your comment I googled T4 converting to T3 there seems to be so many things so confusing


sadly majority of GPs and even endos are very ignorant of the fact that vitamin and mineral levels are crucial for the conversion process and they will even deny t3 matters but it does

theres a huge bunch of info on this issue on tpauk.com

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Hi, this is sherred know how you feel just keep pestering there doctors till they get it right There are lots of thyroid meds i can't take after trying most I'm now on euthyrox but really must take these meds on an empty stomach with water they won't work properly if taken with tea coffee and food ,wait at least 20 mins before eating .good luck


I have always had a tsh result as low as yours, for nearly 20 years, but it never stopped my periods. It also didn't have any other negative effects as I was still under-medicated.

My only thyroid symptoms were due to poor conversion to t3. Knowing the ranges is your best hope of being able to get adequate treatment, as it helps you to have a constructive discussion with your doctor - once you've learned what the levels mean.


Hi there,

I would ask your GP to refer you to an endocrinologist.

You need to be checked for secondary hypothyroidism which is a pituitary disorder rather than a primary thyroid disorder.

They are treated exactly the same way so please don't be alarmed.

I have secondary hypothyroidism.

Usually it presents with low TSH, LOW FT4 and LOW FT3.

You seem to fall into that category. Please ask for the reference ranges to your tests which would make it easier to get a clearer picture.


It strongly sounds to me like you have either central hypothyroid which is different and TSH will always be low or zero

Or you are unable to convert levo t4 into t3 which every cell needs to function

Usually this is due to levels of




Vit d3

Being below halfway in their ranges

Ask your GP to test them too

Be very sure to book blood tests for early morning,fasting and never never take your levothyroxine inmthe previous 24 hours


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