Thyroid UK
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Should I defer blood test due to viral infection?

Hoping I can get good advice re the above.

I am just up out of bed yesterday after having the annual autumn viral infection blinder - chills, fever, chesty cough , head ache etc etc - deep joy!

I am due to have a thyroid blood test tomorrow and i seem to recall that viral inefctions can affect the TSH, I just cant recall whether its more likely to push it up or down, can anyone help please?

Recent blood tests/doses are;

April TSH = 0.04, (0.2-4.5) & T4 13 (9-21) - was taking 75mcgs levo.

20 June TSH = 5.7 & T4 = 11 - now feeling v. tired, advised to up to 100mcgs T4 which I did.

i then went back 4 weeks later for another blood test - results were;

TSH =1.1 and T4 =14 - tho i felt better I still did not feel as good as when my TSH was lower - nice GP allowed me to inc to 125mcgs T4 but I stopped it after 10 days as I felt it was too much so stayed on the 100mcgs.

I have now been wondering if I need more - hence I booked test for tomorrow but wondering if I should defer it as recent lurgy may skew results/

Any thoughts gratefully received, :)

8 Replies

Very difficult to know about the effect of a virus. Quite possibly it depends on which virus? I wouldn't pretend to know and anything I said would be a guess.

However, if 100 isn't enough, and 125 is too much, you could alternate 100 one day, 125 the next. Or two days of 100 and one of 125. Or the other way around. Or, as you must be taking a 25 microgram tablet, you could split that and take 112.5 every day. Somewhere in there might be the optimum dosing regime for you.



Good Morning !I think it may be better to not have it done but ask at the surgery or where your bloods are done first.the immune systum is inportant of the workings of the body.a virus is bound to affect it ...

how do you know 125mg is too much for you ?.you have to give it a chance to work ...if you have too much you will get side effects like paplitations and other symtoms if you have none then 125mg is have to take it to know ! it can make you so much better if on the correct dose........Good Luck!


Hi there thanks for advice - have had blood test this morning - depemding on result I may take more thyroxine - when I took 125mcgs before I had a feeling of pressure in my throat and so went back to 100mcgs :)


I do hope you find a level that suits you best and feel better in yourself is so important to how we feel all round and life itself ......I hope you also get the right advice from your doctors .and be checked .from time to time it is your life !!!.Margaret xx :)


hi again, have got results back TSH up to 2.2, ( was 1.1 last time) and T4 still 14, but nice GP said I could try 125mcgs, so am doing this. Altho the lithium I have to take is not great for thyroids it does mean that I have to have blood tests every 12 weeks to check my lithium levels and they have still been doing my TFTS then as they have yet to stabilise for decent period of time!.:)


Hi !!things seem to be improving for you so that must be good .as long as you are being checked that is fine ..I must check lithium as I do not know that ..aways something to learn...keep improving anyway ..give it time does take time ..........Good Health !!!Margaret


I have checked lithium do you have to have this ? as that is why you have to have bloods checked often you have underactive thyroid, they do not always mix if you do not have to have it better not to ..ask your GP ...


I used to take lithium along with many other nasty things. I no longer need any of them now my thyroid is more-or-less sorted out. It is difficult to know whether my mental health problems were caused by my thyroid in the beginning or the lithium cause my thyroid problems or was it a mixture of both? Who knows? I suspect my thyroid was starting to fail in the beginning but the lithium helped do the rest. I am very happy I don't have to take lithium any more now that my thyroid is better treated. I hope the same is true for you some day. 'Chemical straight jacket' was a very good description. I also lost all my creativity and ability to think about complex stuff with it. It's nice to be able to be my 'mad scientist' self again ;)

Yes, your TSH is rather high. Your T4 could also be higher. I found liothyronine worked much better for me. It also significantly helped my mental health. It may be something worth mentioning if you find you can't increase your thyroxine dose enough to make you feel better.

Carolyn x


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