Medical question - under active thyroid - Thyroid UK

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Medical question - under active thyroid


I am new to this group but have a question.

I was diagnosed with an under active thyroid about a year ago and put on 75mg of thyroxine (I also had anaemia that’s been treated).

The past few weeks I have been feeling exhausted with dark circles under my eyes, an aching body, and mental fatigue.

I thought it was anaemia but the test result confirmed my thyroid was lower and my medication needed to be 100mg per day.

I just want to know if I would feel as low as I sud with just a difference of 25mg needed? I guess I’m concerned there are other medical issues but am hoping that it is all thyroid related?

Any advice would be greatly appreciated.


7 Replies

To avoid sudden or unpleasant symptoms in response to too big an influx of thyroid hormone, it's recommended that increases are gradual, hence a 25 mcg increase. That doesn't mean necessarily, that that's all you need right now, or all you will ultimately need; just that it's a safe and careful way to increase before testing and adjusting again if necessary, in c6 weeks time. However, if you post all your latest thyroid test results and their ranges, (and hopefully your Dr tested more than simply your TSH which is a pituitary hormone), members can more accurately advise you.

Debbie-M in reply to MaisieGray

Ok thank you.


You will need FULL Thyroid and vitamin testing 6-8 weeks after each dose increase

The aim of Levothyroxine is to increase slowly in 25mcg steps until TSH is around one and FT4 towards top of range and FT3 at least half way in range

For full Thyroid evaluation you need TSH, FT4 and FT3 plus both TPO and TG thyroid antibodies tested. Also extremely important to test vitamin D, folate, ferritin and B12

Low vitamin levels are extremely common, especially if Thyroid antibodies are raised

All thyroid blood tests should ideally be done as early as possible in morning and fasting. Do not take Levothyroxine dose in the 24 hours prior to test, delay and take immediately after blood draw. This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip, best not mentioned to GP or phlebotomist)

Private tests are available. Thousands on here forced to do this as NHS often refuses to test FT3 or antibodies or vitamins

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 special offers, Medichecks usually have offers on Thursdays, Blue Horizon its more random

If antibodies are high this is Hashimoto's, (also known by medics here in UK more commonly as autoimmune thyroid disease).

About 90% of all hypothyroidism in Uk is due to Hashimoto's. Low vitamins are especially common with Hashimoto's. Food intolerances are very common too, especially gluten. So it's important to get TPO and TG thyroid antibodies tested at least once .

Link about thyroid blood tests

Link about antibodies and Hashimoto's

List of hypothyroid symptoms

NICE guidelines saying how to initiate and increase. Note that most patients eventually need somewhere between 100mcg and 200mcg Levothyroxine

Debbie-M in reply to SlowDragon

Thank you. That’s really helpful.

I had read that the NHS don’t cover the full checks. I feel so low on energy mentally and physically and was thinking of going private. I will definitely do that following your advice. Kind regards, Debbie

If you've been treated for anaemia does that mean you had blood tests showing that you were no longer anaemic, or did you just get a prescription for a couple of months of iron supplements and then were told that was your lot?

Let's suppose your ferritin was 6 with a reference range of 13 - 150, and your haemoglobin level was under the range. If you were given iron pills for a couple of months your ferritin might rise to 30 with a range of 13 - 150 and your haemoglobin could creep into the reference range. You would then be classed as no longer anaemic and you would not be prescribed any more iron. Given, say, two or three months of no iron supplementing, you could end up anaemic again. But the doctor would refuse to test because you have recently had supplements and tests, so his job has been done (in his opinion).

I suffered from severely low iron, but I decided to treat the condition myself after finding out that I could buy prescription strength iron without a prescription and I could get a full iron panel done with private blood testing just by ordering it over the web. I didn't need a doctor's permission.

It took me nearly 2 years to increase my ferritin to optimal levels. I now maintain my levels by taking a maintenance dose of iron all the time (One tablet 3 or 4 times a week.) I pay for private testing about twice a year now. It is not safe to do this unless you know how well you absorb iron. But once you know your own response to iron you might be able to maintain it relatively cheaply.

Debbie-M in reply to humanbean

Thanks, yes, the GP did test my iron levels and confirmed I was not anaemic. But as I said in my previous post, I will go private for testing. I just feel so unwell ... really appreciate everyone’s response.

humanbean in reply to Debbie-M

For testing iron this is a very good test :

and you can get a discount on the price with the discount given in this post :

No doctor is required and the sample you need can be got with a finger-prick sample and sent through the post.

If you go ahead and get the above test you can post the results into a new post and ask for feedback.

Edit : Iron isn't simple. If both serum iron and ferritin are low then supplementing is a good idea. But if one of those is low and the other high then it implies there is another problem which needs to be investigated first before supplementing iron.

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