Thyroid UK
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Fluctuating thyroid results

Hello everyone. I haven't been here for a while, but I got a lot of help from the lovely people here a couple of years ago and felt well for a while, but unfortunately I am back again for more advice. I was diagnosed with an underactive thyroid 5 years ago shortly after my son was born. I was given 50mcg of levo and even though I still had a lot of awful symptoms was told they couldn't be my thyroid and I was depressed and it was all in my head. It took 3 years, about 8 GPs and one cow of an Endocrinologist before I finally managed to get my levo increased. For about a year I was taking 150mcg and felt really well. I could walk for miles, lost over 4 stone, I got a job that I love and my life turned around. I still had a few symptoms, some brain fog and occasional lethargy and depression, but generally I felt great.

Then a year ago I started to feel underactive again. I was tested and my T4 was low. My GP increased my dose to 175 and my T4 went too high, not dramatically, but enough for me to get hyper symptoms. I decreased to 167.5 and it was still too high. Back down to 150 and my T4 was high again. Down to 125 and it has dropped right down and I am back to feeling exhausted all the time. My TSH has barely moved throughout all those changes. I take my medication first thing in the morning on an empty stomach and don't eat until an hour after, so I don't think it is an absorption problem. I also make sure I always have the same brand of levo.

Does anyone have any idea what could be causing these fluctuations? I have been tested a couple of times for antibodies and they have come back negative, so I don't have hashimoto's.

8 Replies

I think this scenario often happens. Levo works for a while but our store of vitamins and minerals becomes depleted and gradually we stop converting the Levo properly into the active T3 hormone, needed by every cell in the body. You do not give thyroid results. It would help to see the latest and also to get a free T3 test, which I expect will be low. Your Free T4 may be high, hence you TSH will look fine. Ask your GP to check your iron, ferritin, B12, Vit D and Folate. These all need to be high in range - ferritin above 70. Do not start to take any supplememts before the tests. Once these improve you should start to convert properly but the addition of T3 would help you straight away. Unfortunately your GP probably will not give it but an appointment with a knowledgeable Endo might help.

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,,,perhaps it could be your levels of B12 - Ferritin - Folate - VitD etc. Are they all optimal ? If these levels are low then this can cause poor conversion of T4 into the Active T3. You don't mention your T3 levels - perhaps that would help you to understand what is going on.

Do hope you soon regain your earlier health...


I have also suffered what GP's have called 'fluctuating' thyroid levels as indicated by varying test results. However there was an interesting post from someone on here a while ago that said that the drugs efficacy can vary widely, despite what the dose stated on the box says. This person seemed very knowledgeable in this area and worked in the medical profession. Apparently differing tablet batches can register very varied results. It is a good idea to stick to the same brand that you can trust, and go by how you feel. Since moving over to liquid thyroxine I feel my levels are more stable. Some doctors resist giving this out as it is more expensive than the mass-produced tablets but I would personally recommend it.


From a physiological perspective the impact of the changes in hormones may have had an impact on your muscles etc which will in turn leave you feeling unwell and less capable until you have stabilised. (Plus making sure other things are correct eg vits) I'm currently going through this at the moment and hadn't really taken into account the symptom delay. I really think that we unknowingly think we can do what we've done when well, do so, but our body is flagging - it's gradual but probably very bad when we're actually dealing with the symptoms.

I know from experience that when I've wobbled from a fitter level I haven't felt the impact as much as from a much less fit level - specifically my muscle strength. I deliberately trained hard a few years ago to get better at a martial art I do and built up muscle. When I wobbled the symptoms were not as bad as they are currently.

It takes a good few months to both build correct levels and tissues to repair.

I also think that the stress we experience trying to do what we used to do gives extra wear and tear; my physio talked about how cortisol affects muscles etc, literally breaking them down for energy. I know this had been my big issue recently.

Some wobbles can be following illness etc; I'm now very suspicious of thyroxine batches following my experience on TEVA 100s. The range of medicines and foods which can affect absorbtion can be wide too ; I didn't know magnesium does and I've just discovered the sertraline I'm on to help my head following a post natal wobble does a lot too! (Thanks big pharma)

I'm now looking into the possibility of t3 with my dr via an endo.

May I ask how old you are and if there's any possibility of early menopause too? Unlikely but menopausal women I believe need less?

Sadly the thyroid is a really weird organ.


This post menopausal woman doesn't! lol


Or rather, the thyroid system is extremely complicated and can be affected by many things !

I'm wondering if your batches of thyroxine might be to blame? Which one is it? I've had issues this year...


Thanks everyone. I had my B12 and ferretin tested a few weeks ago and they were both near the top of the range. I haven't had a vit D test for a while, so I will look into that.

I am 38, so hopefully not menopause. I did suspect that once before and was tested, but was fine. That was a couple of years ago though. I have the mirena coil and I do wonder if that might be having an effect.

I got a letter from my GP this morning. Last time I saw her she said she was going to look into referring me to an Endo. At my surgery they seem to have to consult a colleague whenever they refer. In her letter she says that as normal levothyroxine treatment doesn't seem to be working for me she has referred me to an endocrinologist. This would be great news if she hadn't referred me to the cowbag endo I saw before! I will call the surgery on Monday and see if they can change the Endo. I really don't want to deal with her again. This does seem promising though as she has acknowledged that levo isn't doing the job. Fingers crossed this will lead to a trial of some other medication.


When you take T4, it either becomes FT3 or reverse T3 (which can wreak problems if too large of a ratio). A blood test of FT3 and Reverse T3 would really be helpful if all other tests show nothing.

Perhaps your first increase of T4 was too high and started the roller coaster.


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