Thyroid UK
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Trial of Levothyroxine

Hi all,

I'm new to this community because I've had a number of symptoms for a few years now, which I never thought were related until my doctor suggested a thyroid test and I did some research online. The first test showed I have subclinical hypothyroidism with the results: TSH 5.1 (range 0.2-4.2) and FT4 17.6 (no range written on my printout). I was told to retest in 3 months and that test came back normal: TSH 3.5 (range 0.2-4.2) with no FT4 tested (or at least not written on my printout).

I've still been getting the symptoms after the second test so I went to the doctor asking about any other tests and the FT4 result. He said they would have tested for FT4 automatically the second time and there aren't any other tests they can do at the moment but agreed to put me on a trial of 25mcg Levothyroxine for 3 months to see what happens.

I've panicked myself a bit as I started using it yesterday morning and I had my really bad headaches back all day and then today I was sick. I know these can be a side effect of Levothyroxine but also a sign of Hypothyroidism (the headaches is one of the symptoms I get) so I'm not sure what to make of it.

I'm a little worried that with the second result saying I was normal that maybe the first test was just a blip and I'm not hypo. The doctor was happy looking at my first results to trial the Levo and the nurse who took my bloods for the second test is hypo and thought I had it from my first result and the symptoms I discussed. The doctor said that it was the lowest dose so there shouldn't be any problem trialing it.

Should I go back to the doctor after a week if it's still the same symptoms and do I need to retest earlier than 3 months? That seems like a long time but as I'm new to this whole thing and I kept checking with the doctor that 3 months was right I just don't know.


11 Replies

You should retest in 6 weeks when first starting levothyroxine as you need to know whether you need a dose adjustment and it takes around 6 weeks for thyroid hormone to saturate all your cells and give a reliable reading. Have you got thyroid antibodies? Check your blood test results. If so, your thyroid blood levels may vary.

As far as I know, being sick is not generally a symptom of an underactive thyroid. Ring your doctor and ask for a telephone apt to discuss your reaction to the tablets and find out if you have thyroid antibodies.

If your results are fluctuating, which it sounds like they are, your underactive thyroid may have become more active and you may need to wait for it to settle down and then try the levothyroxine again, so discuss iwth your doctor.

If you post both sets of blood tests here along with the laboratory ranges then people can give you sensible advice.


Hey. These are the only results I was given so I don't know if they tested for antibodies. I did ask for further testing to be sure but I was told they are the only tests they do.

I will speak with the doctor next week over the phone to be sure of all of this. This is why I was concerned about it all.

Sorry I thought I had put the ranges. I only have the TSH range written on the results, which is 0.2-4.2. So I was over on the first test and within for the second.

Thanks for the advice :)


In other countries we are diagnosed if our TSH is 3+ but if you are in the UK the figure they have decided is 10 and we could be quite symptomatic well before that number.


Welcome to our forum Kezzmin,

Unfortunately, the dose your doctor gave you (as your TSH didn't reach) 25mcg is so small it probably made you feel worse.

In other countries people are diagnosed when TSH is 3+ and I've no idea who pulled the number out of a hat in the UK. By the time it reaches 10 we can feel absolutely awful.

You will find that few doctors know anything clinical symptoms at all. They're told to get the TSH 'somewhere' in the range which is anything up to around 5. If patient complains the are given a prescription for something other than an increase in hormones.

First thing is to get a print-out of your blood test results you had, and make sure ranges are stated. Ranges are required for comments as labs differ.

Put them on a new post for comments. The following are procedures to get the best outcome from the tests. First - before levo and blood tests were invented - we were diagnosed upon our clinical symptoms. You can tick off the ones you have:-

All blood tests for thyroid hormones have to be at the very earliest, fasting (you can drink water) and allow a gap of 24 hours between last dose and test and take afterwards. The tests are TSH, T4, T3, Free T4, Free T3 and thyroid antibodies. (usually only the TSH and T4 are taken which aren't sufficient.) If you have thyroid antibodies it means you have the commonest form of hypothyroidism called Hashimot's and the antibodies atack your thyroid gland and wax and wane until hypothyroid but treatment is the same - levothyroxine.

Usually you take levo when you get up with one full glass of water with one full glass of water. Wait about an hour before eating as food interferes with the uptake of levo.

Some prefer bedtime dosing and if having a blood test next a.m. miss this dose and take after test and bedtime dose as usual.

If you have thyroid antibodies, regardless of where the TSH the GP should prescribe levothyroxine (many are unaware of this).

Ask GP to test B12, Vit D, iron, ferritin and folate as everything has to be optimal and we can be deficient.

Starting dose is usually 50mcg of levo with a blood test and increase every six weeks until symptom-free - and TSH is 1 or lower - not above as many doctors believe somewhere in the range is fine.

It is a big learning curve but members will be helpful.


What test do I need to do for the thyroid antibodies? I asked for further testing and the doctor said they don't do any so I will look into this.

The TSH range was 0.2-4.2 but there was no range given for the FT4. I did ask but that was all the information he could give me.

It I don't have the antibodies is that an indicator that I'm not hypo perhaps?

Thanks for the info by the way :)


He probably couldn't answer your question. I think they've been told the TSH and T4 will suffice but we, the sufferers, know this is not true.

This is an explanation. You want to know if you have an Autoimmune Thyroid Disease, AKA Hashimotos. The antibodies attack the gland until your are hypothyroid but treatment is the same.


We also have recommended labs which will do all of the tests as NHS usually only do TSH and T4. You don't need them every time you have a test but to know the level when you begin and when you are having difficulties/symptoms.

The aim is a TSH of 1 or lower with FT4 and FT3 towards the upper range.


You will have to read, learn and ask questions as few doctors know how to treat us to become well.

First the two main thyroid hormones are T4 and T3. i.e. levothyroxine and liothyronine are provided by a healthy thyroid gland.

When we become hypothyroid our gland isn't producing the hormones that run our whole metabolism. We are prescribed with levothyroxine and starting dose is 50mcg with 25mcg increments every six weeks until symptom free and TSH is 1 or below.

Normal is meaningless if hypo. That's what the term the doctor uses when our results are 'somewhere' within the range. The range we need is a TSH of 1 or lower but doctors mistakenly believe we will have heart problems if our TSH is low or suppressed.

When our TSH is 1 or lower, we are usually on an optimum of thyroid hormones.

Levothyroxine (T4) converts to T3 (liothyronine). T3 is the only active thyroid hormone and is required in our billions of T3 receptor cells. Insufficient and we don't feel so good.

It would be best to have a Full Thyroid Function Test so that you know what is your 'starting' range is i.e. TSH, T4, T3, Free T4, Free T3 and thyroid antibodies. plus B12, Vit D, iron, ferritin and folate. Everything has to be optimal - not in range.

If GP or lab wont do a full thyroid check, you can have a private one from our recommended labs. They do home pin-prick tests

Most important is to have blood tests for thyroid hormones at the very earliest possible, fasting (you can drink water) and allow a gap of 24 hours from your last dose and the test and take afterwards.

Always get a print-out of your results with the ranges and post for comments.

Never accept words 'normal' 'fine' or 'o.k'. We need optimal which is a TSH or 1 or lower and FT4 and FT3 towards the upper part of the range.

Post your results and the ranges.


For full evaluation you need TSH, FT4, FT3, TT4, TPO and TG antibodies, plus vitamin D, folate, ferritin and B12 tested

For peace of mind you might want to get these done ASAP. But ideally you would wait 6 weeks before testing

If you can't get full thyroid and vitamin testing from GP (very unlikely to do all......might do some)

Medichecks Thyroid plus ultra vitamin or Blue Horizon Thyroid plus eleven are the most popular choice. DIY finger prick test or option to pay extra for private blood draw. Both companies often have money off offers.

All thyroid tests should be done as early as possible in morning and fasting and don't take Levo in the 24 hours prior to test, delay and take straight after. This gives highest TSH and most consistent results

As others have said, 25mcg is such a small dose it can make you feel worse. Your own thyroid takes a rest, but the dose is too small to offer support

Always take Levo on empty stomach and then nothing apart from water for at least an hour after. Many take on waking, but it may be more convenient and possibly more effective taken at bedtime


So is it worth getting the test now before I continue with the levothyroxine? I've only had the one tablet so far so I could get the tests done this week and start again after or should I continue, test and then see my doctor?

I took the tablet early morning yesterday but planned to take it before bed from tonight onwards to be safe.


Up to you. If you can stick it out for 6 weeks then go for it.

You could even carry on on 25mcg and still do the private test. TSH would be a bit irrelevant, but rest would be fairly accurate.

Only do private tests Monday, Tuesday or Wednesday as has to be posted back and processed before weekend

Unless using walkin London clinic


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