Why is my TSH below range and my T4 levels are ... - Thyroid UK

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Why is my TSH below range and my T4 levels are dropping?

rosie61 profile image

Hi, I have been hypo for 25 years and have been on thyroxine. My last four blood tests have shown that my have shown that my T4 Level is dropping as the doctor has reduced my thyroxine dosage on three previous occasions. My last blood test showed that my TSH is still below range.

2015 tsh 0.04 range 0.27 to 4.2

T4 22.5 range 12 to 22

2016 tsh <0.01 range 0.27 to 4.2

t4 22.5 range 12 to 22

july 2017 tsh <0.01 range 3 to 5 t3 5.5 range 3.8 to 6

t4 18.8 range 8.4 to 19.1

sept 2017 tsh 0.01 range 0.3 to 5

t4 13.3 range 7.9 to 16

dec 2018 tsh 0.04 range 0.3 to 5

t4 13 range 7.9 to 16

I have been called to say I need to make an appointment as my tsh levels are out of range, but my t4 looks fine to me as going by the original ranges I am about midway, by the new ranges I am top end...………………. I know he is going to say I need to reduce my thyroxine but I know I will feel worse than I do now. I am currently on 125 mcg. Last year I was really poorly and eventually got a blood test in the july where by b12 was so low I had to have six injections and now am on injections every 12 weeks, and I really can tell when they are due! I am 57 and my periods stopped when I was about 38 approx. 5 years after being diagnosed with hypothyroidism. I now have adult acne ( strange because I never had it when I was a teenager.) I still struggle with my weight and tiredness. Okay that off of my chest, does anyone have any advice as how I can explain to my doctor why I do not want to decrease my thyroxine. thank yo

7 Replies
SlowDragon profile image

When under medicated on levothyroxine vitamins drop

When vitamin levels drop then TSH drops

That’s why it’s completely inadequate just testing TSH and FT4

You have low vitamin B12 because you are under medicated

Full thyroid and vitamin testing is essential

TSH, FT4 and FT3 plus both TPO and TG Thyroid antibodies

And vitamin D, folate, ferritin and B12

Vast numbers on here forced to test privately as NHS refuses to test both antibodies, FT3 and often refuses all four vitamins

All thyroid tests should be as early as possible in morning and fasting and no levothyroxine in the 24hours prior to test

Medichecks or Blue Horizon are private testing options

Come back with new post when you have results and ranges

Likely vitamins are all very low

An fT4 of 13 (7.9 - 16.0) is ideal for many patients (not all). Your TSH is abnormally low for this fT4. This indicates that your thyrotrope (TSH secreting part of pituitary) is not responding normally, perhaps because you had high hormone levels sometime in the past which have blunted its response. Ideally your doctor would measure fT3 also but this is usually refused if a GP requests it. I would keep your fT4 within its reference interval and if you still feel tired ask for a prescription of liothyronine (L-T3), you will probably need a referrral to an endocrinologist to get this but insist, don't let it rest. Antibodies are of little use now, if high antibodies led to your hypothyroidism it's pretty much history and doesn't affect your need for thyroid hormone. Having ferritin measured is a good idea as hypothyroidism often leads to lower iron levels.

MiniMum97 profile image
MiniMum97 in reply to jimh111

Hi Your comment about a blunted TSH response is interesting as my TSH seems to be slow to respond. Do you have any evidence/studies that talk about this phenomenon? Many thanks.

SeasideSusie profile image

my t4 looks fine to me as going by the original ranges I am about midway, by the new ranges I am top end

You can't mix and match ranges. These are your actual percentages through the range for each result:

2015 - t4 22.5 range 12 to 22 - over range at 105%

2016 - t4 22.5 range 12 to 22 - over range at 105%

july 2017 - t4 18.8 range 8.4 to 19.1 - 97% through range

sept 2017 - t4 13.3 range 7.9 to 16 - 66% through range

dec 2018 - t4 13 range 7.9 to 16 - 63% through range

If your Levo is reduced now, it will reduce your FT4 to an even lower point in the range, and you will become more hypo and more symptomatic.

To avoid a further reduction, use the following information from Dr Toft, leading endocrinologist and past president of the British Thyroid Association, who said in an article in Pulse magazine (the magazine for doctors):

"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)."

He recently confirmed, during a public meeting, that this applies to Free T3 as well as Total T3.

You can obtain a copy of the article by emailing Dionne at tukadmin@thyroiduk.org print it and highlight question 6 to show your doctor.

However, he also recently published another article where he says some people benefit from the addition of T3 to their Levo


I would do as SlowDragon has suggested, get a full thyroid panel with vitamins and minerals, post the results here for further comment

Medichecks Thyroid Check ULTRAVIT medichecks.com/thyroid-func... - use code THYROIDUK for 10% off any test not currently on special offer


Blue Horizon Thyroid Plus ELEVEN bluehorizonmedicals.co.uk/t...

I went through exactly the same thing. To get straightened out, I had to get completely off all meds,wait and change doctors . I do not recommend doing this, it was horrible. The answer is to get on a natural thyroid extract and never take thyroixin again. I have remained stable for years since switching back to good old desiccated pig thyroid. BTW, TSH actually shows what your level was 6 months ago, so if your doctor is measuring it more often it is not accurate at all.

Thank you for your responses. I will look in to it all the information you have given me. I will probably ask for a referral to try and get this sorted.

SlowDragon profile image
SlowDragonAdministrator in reply to rosie61

Ask GP to test vitamins and thyroid antibodies, FT3 alongside FT4 and TSH.

Or getting private testing is likely necessary

Making sure to do test as early as possible in morning and fasting and no Levo in 24 hours prior to test

If you want to see an Endocrinologist, it's important to pick the right one. Most are only Diabetes specialists

Email Thyroid UK for list of recommended thyroid specialists. Some are NHS and private.

please email Dionne at


NHS waiting time is often several months, especially since new rules means GP's can no longer be prescribing T3.

GP's do not want to refer patients as cost of prescribing T3 comes out of their budget

New NHS England Liothyronine guidelines November 2018


Dossier presented to Lord O'Shaughnessy November 26th


Media coverage showing widespread stopping of T3


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