Thyroid UK
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is it best to book blood test for early morning or late afternoon?

Been on levothroxine for 2 years 25mcg, then 50, 75 100 , 125 and now back to 100. But my symptoms feel no better ( lank hair that is falling out, pains in my bones . muscle weakness, confused, very very tired, muscle spasms in my neck, enlarged glands )etc and many more symptoms the list goes on and on. I think i need a higher dose but dont know if i will get a better result if i get my bloods taken early morning or last apointment, and should i take my tablet that day like i normally do approx 6.30am. Hope someone can advise.

thanks. x

6 Replies

I believe it's best to have bloods taken early morning and not to take your tablets beforehand.

regards x



But do remember to take them straight after.



Don't panic about taking your meds straight after blood tests as thyroxine has an eight day half life unlike T3 which is an 8 1/2hrs half life.



Certainly don't panic. But the longer it is left before catching up, the closer it gets to your NEXT dose - so you could end up taking two doses within much less than a day. Or if, like me, you are one of those who does not often notice a fairly immediate effect you could easily forget until later, or even altogether.

Further, while the half-life of thyroxine is indeed reasonably long this is a bit misleading. The half-life does not mean that it cannot be used up faster than that. Consider this, if you are taking 100 mcg a day then you are using up thyroxine at a rate of 100 mcg per day. By 12 hours you might be down by 50 mcg. Without a doubt many people can feel that sort of a difference readily. I know someone who visibly changes with amounts as small as 12.5 mcg. In her case I would not be surprised if she noticed delaying a dose by as little as 3 hours - or even less.

(Obviously this is a gross simplification for illustration.)



Always have a test early in the morning and don't take meds for 24 hours before a test.... Thyroxine is best taken at night (there was a thread on here, recently)....

Are you taking selenium daily to help conversion of t4 to t3? Plenty of vitamin C to assist adrenals (min 1000 mcg). Do you know any of your results? Is your free t4 towards top or over the range? Is tsh below 1? How much free t3 do you have?. If you don't have all these results because the doctor isn't getting the proper tests done, then get them done privately... TSH, Free T3 and free t4 tests done together costs £51.

If you know where you are with these, then you'll have a starting point so you can work out what is going wrong.... It could be non conversion, cellular resistance, insufficient hormones, without some test results to start with, you're just in the dark.

Ask your doctor first, for the results (and the ref ranges) of any tests he may have done. These are you'rs by law, and he cannot refuse to give them to you.



Just to confuse things, I have always been told to have the tests done later in the day and at LEAST 12 hours after your last dose. (I take my T4 last thing at night) Last year I was most confused by an endo telling me to take my dose and then have the test! Everyone I have mentioned this to has been puzzled likening it to asking a diabetic to eat choc prior to being tested....... getting a false high reading.


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