Thyroid UK
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What is the normal range for T4 please?

Hi. My levothroxine has been increased from 75mcg to 100mcg. Latest lab results are as follows:

TSH 2.88 (Range 0.34 - 5.6)

T4 12.7 (No range given)

T3 4.3 (Range 3.8 - 6.0)

I still have hypo symptoms and am still gaining weight. Since prior to being diagnosed i have put on 5 stone. Can anyone help? I am wondering if maybe increasing Levothyroxine to 125mcg might help? I have seen an endocrinologist who was next to useless and who suggested that maybe i was treated to early despite having most of the symptoms and a starting TSH of 9.28 and having thyroid antibodies! I'm really fed up, this has been going on for years.

6 Replies

Hi. Your tsh seems too high still. When you say they've increased your levo, is this test from before or after the increase? Ideally you should be allowed to maintain your tsh below 1 to see if it helps you feel better, so keep that in mind as a goal.

The range for t4 varies among labs so they should give you theirs. Can you ring either your gp or the lab to ask? According to TUK the approximate range for free t4 is 10-24.


Hi. This lab test was ran 6 weeks after increase to 100mcg from 75mcg.


I'm not a doctor but it looks to me like you need an increase. Your tsh is too high and your t3 and t4 seem (with the info available) to be too low.


It is despairing the number of doctors who believe the patient is well when their TSH is within range. Ignoring the clinical symptoms and telling them that 'it's not your thyroid gland'. It's due to something else. You will see the recommendation for the TSH and yours is most probably too high.

This is an extract from an article in Pulse Online by the ex President of the BTA. email and ask for a copy. Give a copy to your GP before your next appointment to discuss. Also never take your meds on the morning of your blood test, which you should have as early as possible, take them afterwards. If you take a night dose, miss this and take after test.

6 What is the correct dose of thyroxine and is there any rationale for adding in tri-iodothyronine?

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).

Even while taking the slightly higher dose of levothyroxine a handful of patients continue to complain that a sense of wellbeing has not been restored. A trial of levothyroxine and tri-iodothyronine is not unreasonable. The dose of levothyroxine should be reduced by 50µg daily and tri iodothyronine in a dose of 10µg (half a tablet) daily added.


I would love to try some T3 but i believe thats akin to finding gold! Since posting my GP has upped my meds to 125mcg for 3 months so we'll see if this offers some help! Thanks for your replies.


Getting it on the NHS is not always easy, but you can buy it online


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