Thyroid UK
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Why do I have to lower thyroxine?

Hi guys,

I had a blood test to check my thyroid and yesterday I had a phone call from my doctors surgery to tell me that doctor has said I have to only take 50gms of thyroxine now (I was on 75 for a few years and have felt fine). I have an appt next Thursday with the doctor as I want to know why I have to lower my dose. The receptionist couldnt help me, she said that it looks like my TSH is low but she wasnt sure.. Ive no idea what that means and can it be dangerous if tsh is low. Could anybody here enlighten me?

Many thanks Tasia.

7 Replies

I don't think anyone on here can advise you correctly unless you get copies of your blood results and then post them on here (with ranges).

Your TSH can be lower than what the GP's term normal with no ill effects as they are following NHS guidelines that are pretty useless. Some people (myself included) only seem to feel better with a TSH of one or under and seeing as the NHS top guideline in approx five you can then start to see why some patients are left to suffer when a GP follows these figures.

Ask for a copy of your blood results (the receptionist is better for this) and then post them on here for people to comment.

Try to persuade your GP not to lower your dose if your TSH is not incredible low (something like 0.03 will cause a GP to panic) stating that you were feeling fine on 75mcg's but if she insists on lowering your dose ask her for a reassurance that if you start feeling ill on the lower dose she will let you go back up to 75mcg's, or do alternate days of 50mcg's and then 75mcg's. Also make sure she agrees to a blood tests after eight weeks on a lower dose to check your levels as some GP's will lower your meds and then not check how you are doing.

Don't worry to much over a low TSH level - the TSH test just tells the GP how much thyroid hormones the body is asking for but this test isn't always a true reflection on how the patient feels and symptoms need to be taken into account as well.

Moggie x


Just a correction Moggie. There are no NHS guidelines for hypothyroidism. There is a non referenced statement (not a guideline) from the BTA and the RCP and self proclaimed "UK" guidelines on Thyroid Function Testing by the BTA. Both the BTA and the RCP are private organisations and have no connection with the NHS. Anybody can write guidelines and call them UK guidelines!


Tasia, I agree mostly with Moggie above but add that any change in your medication had to be made with your agreement according to the doctors Code of Practice - Good Medical Practice. To rephrase Moggie if you feel well on your present dose and you don't have signs or symptoms of too much thyroid hormone, why change dose?

Your GP will probably tell you that a low TSH will lead to heart problems and osteoporosis. If he does he is mistaken. The evidence that claim was made on has been discredited and there is plenty of evidence to show no connection between osteoporosis and thyroxine.Here is the paper to reference

Is it safe for patients taking thyroxine to have a low but not suppressed serum TSH concentration? Graham Leese & Robert Flynn University of Dundee, Tayside, UK.

The paper concluded:

People on long-term thyroxine with a high (>4.0 mU/l) or suppressed (=0.03 mU/l) TSH are at increased risk of cardiovascular disease, dysrhythmias and fractures. People with a low but not suppressed TSH did not have an increased risk of these outcomes in this study. It may be safe for patients treated with thyroxine to have a low (0.04–0.4 mU/l) but not suppressed (=0.03 mU/l) serum TSH concentration.

So as Moggie said if your TSH is above 0.03mU/l, there is no need to change your dose.


How about this letter if things don't go well? if you want to use it, please print out the 2 papers referred to and attach to your letter..

You can copy and paste this letter and amend it as you like to suit your circumstances.

Dear Doctor… …

You have told me that you wish to reduce my dose of Levothyroxine. Unfortunately you have not told me why you wish to do this nor have you given me the information I need to understand your reason for unilaterally wishing to reduce my dose of Levothyoxine. I remind you that Good Medical Practice places a duty on you to work in partnership with me (paragraph 49) and to provide me with information I need (paragraph 32). According to paragraph 31 of Good Medical Practice, you have a duty to listen to me, take account of my views, and respond honestly to my questions.

I am feeling well on …..mcg of Levothyroxine. I do not feel well on any dose below that. It is therefore logical that …. mcg is the right dose for me. Any dose below …mcg will cause me pain and distress. I remind you that, according to paragraph 16c of Good Medical Practice, you have a duty to take all possible steps to alleviate pain and distress. I remind you that, according to paragraph 47 of Good Medical Practice, you have a duty to treat me as an individual. Consequently I cannot see any logical reason to reduce my dose. Please be aware that, according medical negligence case law, a doctor’s course of action has to be logical. Reducing a dose that I feel well on to a dose that I do not feel well on is not logical and may be seen as negligent practice.

If you think that my TSH is too low please be aware that TSH is not a good indicator of health when patients are on Thyroid Replacement Therapy. Please read the attached paper - Is Pituitary Thyrotropin an Adequate Measure Of Thyroid Hormone-Controlled Homeostasis During Thyroxine Treatment? ).

You may think that low TSH leads to osteoporosis or heart problems. That is not so and there is a lot of evidence to support this view. Please read the attached paper - Is it safe for patients taking thyroxine to have a low but not suppressed serum TSH concentration?

I remind you that, according to paragraph 16b of Good Medical Practice, you have a duty to provide effective treatments based on the best available evidence. The papers referred to above represent best current evidence. Furthermore, you should treat the discussion you have had with me (or this letter) and the information I have given you as an opportunity for informal learning and reflection about your performance that has arisen spontaneously from your day-to-day practice. This is in accordance with paragraph 8 of Good Medical Practice and paragraph 12 of Good Medical Practice supplementary guidance Continuing Professional Development.

Please treat this letter as a complaint and put this letter in your portfolio of evidence for your annual appraisal and for revalidation.

If you do not maintain my dose of Levothyroxine at ...mcg, I may make a formal complaint to the Clinical Commissioning Group or the General Medical Council.

Yours Sincerely,


Thankyou very much for the letter, I will see what my doctor has to say next week and if im not happy with her reply. I will than go ahead and give her this letter.

Many thanks you have informed me very well and now I know what I need to ask and say. Thankyou again Tasia x


What a letter!

I would also complain at being told by someone who is not medically qualified to reduce my dose, without explanation (which should have been to the hand of the person ringing), and without that being backed up by a letter or other permanent record.


Hi guys,

Thankyou both for replies. Ill phone up my doctor and get my blood test results and put them up.. Yes I feel fine and I dont really want to start messing around with my dosage incase I start feeling unwell. Ill mention all what you have said to my doctor too..Many thanks I really appreciate it. Tasia xx


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