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Thyroid UK
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Timing of NDT for blood test

I normally take my NDT in two doses - early morning and afternoon. I am doing a finger prick blood test tomorrow morning. Would it be okay to take my last dose of NDT at around 8.30pm tonight and do the blood test at 8 am in the morning?

Also, is it really important that I don't eat until after the blood test, as i might find doing the finger prick test difficult if I'm really hungry, as I tend to go light-headed and feel shaky? Does eating before the blood test only affect the TSH and would this matter if you're on NDT?

Thank you.

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Rachel

Last dose of NDT should be 8-12 hours before the blood test, so taking your NDT at 8.30pm and doing your test at 8am is fine.

Eating can possibly affect TSH (as can coffee) but if that result isn't important then it's no problem if you have your breakfast. Eating doesn't affect any other result, it's only the timing of the last dose of thyroid hormone that affects results of FT4 and FT3.

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Brilliant, thank you.

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Would there be a significant difference in the FT3 result depending on whether one takes their NDT all in one go the evening before the blood draw vs. dividing the dose, half in the morning and half in the evening before the blood draw (8-12 hours before blood test)?

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Does coffee (caffeine?) raise or lower the TSH?

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I don't know. I just know that Diogenes mentioned in one of his replies that "Coffee affects TSH" he didn't elaborate on how it does.

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Interesting. Cheers

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My lot all leave 24 hours from last ndt to the blood test otherwise test gives too high a result

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I didn't see your reply you have several people to go on. I should have left mine off for 24/27 hours then.

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Everyone is different and some endos or GPs are more tricky than others

If in doubt and you do not want dose reduction hassle then 24 hours and feeling rough for a day or so is worth the agro

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I never visit the GP or Endos just self medicate. I will find out maybe when I receive the results tomorrow. I will post them on the site.

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That's exactly what I did yesterday and took one at 6am, second dose at 2.30pm I also took a third dose at 8.30pm. It's not an exact science, is it very hit and miss. Hoping for the best.

It's easy for people to say to leave of NDT for 10/12 hours before the test which is supposed to be first thing it's another to try and do it. I actually took a half extra grain at 8.30pm exactly what you are going to do. It cannot be right just hope. The thing is this if you are doing the blood test yourself and also self medicating it's hard. I did the same last year so that both can be compared to each other.

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I took my last dose at 8.30pm and couldn't get to sleep until 4am. I then started to do the finger prick test at 7.50am and I could hardly get any blood out. I was there for about an hour and ended up pricking 6 fingers and still couldn't get enough blood. A few months ago when i did a finger prick test I had a shower first and I think that made the blood flow easily. I'm going to retake the test as soon as the bruises on my fingers have gone.

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My daughter tried a finger tip blood test and in the end had to rely on a razor blade.

I only have mine done once a year usually so pay for the nurse to come and do it.

The cost £39.

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