Blood Testing Question: Does anyone know what is... - Thyroid UK

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Blood Testing Question

mitchell66 profile image
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Does anyone know what is the ideal time to take a blood test to indicate how you are doing on a certain level of T4. How long before it gives a true reading of how this dose is affecting your levels.

I am asking because my doc wants to wait 8 weeks, does that seem a long time to anyone?

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mitchell66
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PinkNinja profile image
PinkNinja

8 weeks after starting thyroxine isn't a bad length of time, although he should have been increasing your dose every few weeks until you find your symptoms start to disappear. It can take around 4-6 weeks for each increase in dose to have it's full effect so you don't want to have your blood test too soon.

It is best to have blood taken first thing and before you take your thyroxine.

Don't go just by blood tests though. You also need to go by how you feel. Dr Toft, former chair of the British Thyroid Association recommends that you take a dose that gets your TSH below 1 and your T4 near the top of the range. Just being in the "normal" range isn't good enough.

I hope that helps a little bit

Carolyn x

mitchell66 profile image
mitchell66 in reply to PinkNinja

Thanks Carolyn, didn't want to mention Dr S as it might change peoples answers, I see him in 2 weeks and he wanted me to be on 125 before that with blood test results. But my doc has decided they won't do blood test for another 4 weeks which means I have been on 100 for 8 weeks instead of 4, and won't up my dose as requested by Doc S :(

So do I get some home bloods for Doc S or play ball for 4 weeks with the GP and change my appointment. I have not seen any improvements as yet :'( was looking forward to go up to 125.

PinkNinja profile image
PinkNinja in reply to mitchell66

100mcg is still a fairly lowish dose. Can you phone or email Dr S to see what he suggests about the blood tests? He will be able to let you know whether he wants you to get private tests or whether it is ok to wait another 4 weeks. Can he prescribe you the increase? I know it would be more expensive that way, but it might be a solution. I suppose it depends on how expensive. The medication itself only costs a few quid but I don't know if there are other private prescription charges involved.

Dr S knows what he is doing. The GMC know that he knows what he is doing. It's just a few GPs and endos who don't like to think they don't know what they are doing (they don't know what they are doing!) and therefore report him (repeatedly!) to the GMC.

If you are already up to 100mcg, then a blood test after 4 weeks sounds sensible. It's not like you are starting with 50mcg and increasing every few weeks. Then it would be sensible to wait 8 weeks, but not in your case.

Hopefully Dr S will be able to advise. Your GP is not being at all helpful :(

Let us know how you get on.

Carolyn x

greygoose profile image
greygoose in reply to PinkNinja

Hate to disagree, but I really do think it's best to wait six weeks to get the full effects of the previous increase. It takes at least that to get a true reading and for the increased dose of levo to start being converted into T3.

PinkNinja profile image
PinkNinja in reply to greygoose

You're probably right :D I do seem to remember someone saying 6 weeks a while back. It's been so long since I was in that situation. I don't even bother with the blood tests now, except the annual one and I don't pay much attention to that. I go by how I feel and so did my GP. Shame he wouldn't prescribe NDT or T3 though as levo doesn't work for me.

C x

greygoose profile image
greygoose in reply to PinkNinja

Oh, I quite agree with you. Can't remember the last time I had a blood test, I go by symptoms too. But if you're going to do it, best to give it a fighting chance of being accurate. lol

PinkNinja profile image
PinkNinja in reply to greygoose

Definitely :)

mitchell66 profile image
mitchell66 in reply to greygoose

Thank you greygoose, to be honest when I re-read Dr S letter I think he advised blood test just for the GP's sake, he also just goes by symptoms as you know.

The other problem tho is do I go up to 125 anyway?? I have enough 100's spare to make up the difference :o

What would anyone else do? a month is a long time to feel ill if the extra 25 would help

greygoose profile image
greygoose in reply to mitchell66

Personally, I would go up anyway. But then I'm a self-treater so that doesn't sound like an unusual thing to do. If the extra 25 doesn't help, or makes you feel worse, you can always stop taking it again.

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