Thyroid UK
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Is Thyroxine dosage correct?

Am I on right dose of thyroxine?

I've been on thyroxine for few years but still don't feel well. In January my test results were

T4 13.4 (12-22)

TSH 0.03 (0.27-4.2)

I was told to take 125mg of thyroxine and retest in 6 months, in June my results were

T4 14.4 (12-22)

TSH 1.10 (0.27-4.2)

I was told to remain on 125

Any help understanding what's going on would be appreciated

6 Replies

Disey Well, you don't seem to be doing very well on it do you :(

What was your dose of Levo in January before the change to 125mcg? Was it an increase or decrease? Whatever it was hasn't helped you one bit. Your TSH has risen and your FT4 is still very low in range.

Dr Toft, past president of the British Thyroid Association and leading endocrinologist, wrote this in a Pulse Online magazine article:

"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)."

If you email she will let you have a copy of the article which you can print out and show your GP.

You need an increase in your Levo to get you where you need to be as far as FT4 and FT3 are concerned to alleviate your symptoms. Don't let your GP dose by TSH alone, which is what most of them seem to do. The TSH is irrelevant once we are on thyroid replacement.

It would be really useful if you could get the following tests done, in addition to TSH and FT4:

FT3 - this is the active hormone, T4 is the storage hormone and converts into T3 which does all the work, it is needed by every cell in the body and we need to know that we have enough T3.

TPO antibodies

TG antibodies (but NHS doesn't seem to do that one for some unknown reason)

The two antibody tests will tell you if you have positive thyroid antibodies which cause autoimmune thyroid disease aka Hashimoto's.

Also needed are:

Vit D




These vitamins and minerals all need to be at optimal levels (not just in range) for thyroid hormone to work. They are very important.

If you can't get these tests done through your GP then get them done privately with a Blue Horizon Thyroid Plus Eleven test because it looks like you are going to need to start helping yourself.

1 like

I had been on differing doses prior to the tests in January, including having tried t3 and then armour thyroid, still felt poorly so gp put me back on thyroxine at 125 to see how I went. My vit d has been out of range for ages varying from 37-51 (50-150) and most recent test was 48. My ferritin was over range at 344 (25-300). Magnesium 0.73 (0.7-1) I'm confused with all this. I'm inconstant pain, joints and muscles ache and fatigue and brain fog is driving me mad, I am constantly hot too


OK. Do you have any test results for when you were on those different meds?

I have tried all sorts over the last 20 years (was previously OK on Levo only for 20 years). I've had Armour, Armour plus T3, T3 alone, generic NDT, finally back on Levo. Never felt well on anything.

I've recently done a barrage of private tests as a last ditch attempt to try and get well. I found there was a problem with adrenals and virtually non-existent sex hormones (I am well past menopause). I was also not converting T4 to T3 very well and I was severely deficient in Vit D and ferritin and folate very low. I've added some T3 to a lower dose of Levo and am addressing everything else, things are gradually improving.

Your Vit D needs raising to 100+. Are you supplementing? If not then you need a D3 supplement, 5000iu daily for a couple of months then reduce to a maintenance dose of 2,000iu daily. Keep an eye on it by retesting (City Assays fingerprick bloodspot test £28 if your GP wont do it) twice a year to ensure you don't reach too high a level where toxicity is a problem (220 according to City Assays). The Vit D should help with the aches and pains.

When taking D3 we need to take K2-MK7. Vit D aids the absorption of calcium from food and K2 directs it to bones and teeth rather than arteries and soft tissues. It's also recommended to supplement with magnesium when taking Vit D, most of us need it anyway.

Testing for magnesium isn't reliable.

You really do need those other tests I mentioned. It might also be worth doing the Genova 24 hour saliva adrenal stress test. That will give a complete picture (apart from sex hormones, that's expensive to do privately so see what the others show first) and once you have the results then post in a new thread (along with reference ranges) and members can advise and make suggestions.

1 like

Thanks for replying, going to look into getting some private tests done, think that's the best step to take at mo


I think what you need most is a doctor that understands thyroid. But they are sooooooo hard to find.

Have you never felt well on any dose of anything? How much T3 were you taking? How much NDT? Now that you're back on T3 only, the best thing you could do would be to get private tests done that will test not just the TSH and FT4, but also the FT3 and antibodies. You can get a finger-prick test that covers all those, plus the essential vitamin and mineral tests that Susie mentions above.

There was absolutely no point in testing your magnesium, because it will always be in range. But, that doesn't mean you aren't deficient. Why not just take some, see how you go.

Your ferritin was high, but that doesn't mean much on its own, either, because it could have been high due to inflammation. You really need to have a full iron panel done.

Other things you can take without testing, are vit C and selenium. The vit C will help with inflammation, and the selenium will help your body to synthesise the thyroid hormone. For the pain, you could try zinc, and/or curcuma + Piperine.

1 like

Thanks for your reply, we have a new dr now at our practice and haven't heard that he is very understanding, going to get some private tests done I think, thanks again


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