Why do I have to lower Thyroxine (update)..Bloo... - Thyroid UK

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Why do I have to lower Thyroxine (update)..Blood tests results.

Tasia profile image

Hi Guys,

some of you helped me last week as I was told by my doctor that I have to lower my thyroxine from 75 to 50grms, which I cant understand as I feel absolutely fine. You told me to put my blood test up so here they are.

Serum free T4 level 13.9 pmol/L (9.0-22.7).

Than on another page I have:

Serum free T4 level 16.6 pmol/L (9.0-22.7)

Serum TSH Level LO 0.24 mu/L (0.35-5.50).

and thats it..I dont understand any of it...Thankyou for any help.

13 Replies
shaws profile image

If you are feeling fine on 75mcg do NOT reduce. Doctors tell you how you are by only taking into consideration the TSH result. This is an excerpt from Dr Toft, ex of the British Thyroid Association and if you need a copy of the whole article to give to your GP, email louise.warvill@thyroiduk.org

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.


Go to the question dated November January 25, 2002 to read the whole question/answer


Dr Lowe: Your observations don’t suggest to me that your pituitary gland isn’t functioning properly. In fact, your observations are consistent with what science tells us about a patient's T4 dose, her TSH level, and her metabolic health or lack of it. If the goal of a doctor is metabolic health for his patient, he has no scientific basis for adjusting her thyroid hormone dose by her TSH level. If the doctor is going to make the imprudent choice of treating the patient with T4 (rather than T3 or a T3/T4 combination), he should be aware of the relevant physiology and treat her on the basis of it. Otherwise, he's likely to ruin her health, as your doctor appears to be doing to yours.


Thankyou for all your help. Im not a very confrontational person and im extremely worried about seeing my doctor on Thursday and explaining this to her as I have a feeling she may not listen. Thankyou again much appreciated. I may have to photocopy lots of stuff for her to read.

helvella profile image
helvellaAdministrator in reply to Tasia


You results show FT4 only very slightly above the mid-point of the range. In my opinion you could be at the top of that range and still not be taking too much!

Basically, the Free T4 test says how much thyroid hormone is available to you.

By the way, what time of day did you have the blood taken for these tests? And did you take your levothyroxine before the blood was drawn?

Also - if you click on the blue Reply to this, then the person you are responding to gets an alert email so they know you have responded! :-)


Tasia profile image
Tasia in reply to helvella

Hi Rod,

I had my blood test taken 9.30 in the morning. I didnt take any thyroxine on the morning of the test. Thankyou for your reply.

helvella profile image
helvellaAdministrator in reply to Tasia

That's good Tasia!

I am sure you can manage it. And the doctor might actually be quite amenable when it comes to it. You can always hope. :-)

RedApple profile image

Tasia, you don't really need to photocopy lots of stuff for your GP. The little book written by endocrinologist Dr Anthony Toft called 'Understanding Thyroid Disorders' has the following information:

Q. I feel better when I am taking a higher dose of thyroxine than recommended by my doctor. Is this safe?

A. There is considerable debate about the correct dose of thyroxine. The consensus is that enough should be given to ensure that levels of T4 in the blood are at the upper limit of normal or slightly elevated and those of TSH at the lower limit of normal, or in some patients undetectable.

You could simply take this book and show this bit to your GP to prove that your dose of levothyroxine should not be lowered, because even though your TSH is slightly below the range, your FT4 is not even near the top of the range.

Book is readily available in local pharmacies as well as online through Amazon

Amazon link: amzn.to/zQ7dVm

Be brave and stand up for what you are entitled to, which is the appropriate dose of medication that makes you feel well! Good luck, you can do it :)

Tasia profile image
Tasia in reply to RedApple

Thankyou red apple, Ill have a look for the book to see if its in any local chemists.

I know ill have to be strong, but im terrible at trying to explain things, especially to doctors I know im going to get all my words muddled up. Thankyou for your help.

diggercase profile image
diggercase in reply to RedApple

speak to your doctor before you take more than prescribed. you could end up with an erratic heart rate ,doses are set for a reason

Tasia profile image
Tasia in reply to diggercase

Ok, Thankyou for advice. Tasia x

Hi Tasia. Try to be strong :) Knowledge is power and if your Dr thinks that you've done your homework he or she will probably be less likely to dismiss your opinion or feelings about this.

Remind yourself, when in the waiting room, that you deserve to feel as good as you can. We all do. Your Dr owes it to you and to all his/her patients to do what they can to help you achieve this. That is their job! Take care.

Tasia profile image
Tasia in reply to Wired

Thankyou for kind advice. :)

Hi Tasia,

My view is that the dose that is best for you is the dose that you feel best on. I would not rely too heavily on the blood test results, but they can used as an additional diagnostic tool.

Hypothyroidism is a real disease, not simply a manifestation of blood tests.

Your doctor has a duty to treat you as an individual - it says so in Good Medical Practice.

If he is diagnosing you by blood test results, he is referring to a range of results taken from a sample of a population i.e at least 200 people, when he should be looking solely at you and what is right for you.

A reference range represents the range of results of a number of people. Your own set point could be anywhere in that range, or even some place just outside that range. That is why I say that the dose that is best for you is the dose you feel best on.

Remember, the doctor has to work in partnership with you and if you stand your ground he shouldn't reduce your dose.

if you think you will get your words muddle up, please make some notes and take them in to the doctors with you. If you are the same Tasia I responded too previously, I drafted a letter for you. You can print that off and use it as a prompt when you are in the surgery. I also suggest taking someone in with you to give you confidence, back you up when you get tongue tied and witness any thing that the doctor may say. Most doctors are more on their guard when someone else is in the room.

Don't forget that fears of heart problems and osteoporosis are greatly exaggerated. Heart problems are more likely if your dose is too much for you, giving you symptoms of too much thyroxine e.g. palpitations sweating etc.

Osteoporosis has more or less been discredited as a complication of taking thyroxine.

Most people are OK if they don't have symptoms of too much thyroxine.

Be strong and stand up for your self. They work for you and its their job to make you well.

Tasia profile image
Tasia in reply to NBob

Yes I am the same Tasia...Thankyou again for all your kind advice and help to me I really appreciate it.

Tasia x

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