Timing of NDT when having blood test: Please can... - Thyroid UK

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Timing of NDT when having blood test

Lynneypin
Lynneypin
β€’11 Replies

Please can I just check: I am taking NDT last thing at night, so if I'm doing a blood test the next morning, I know skip that dose, but do I then wait until the following night for another dose?

Thanks for all the help.

11 Replies
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Once you have had the test you can take your morning dose, you dont need to skip it altogether. It wont hurt that its a bit later than normal, many people take it all in one dose anyway.

I take it you know to have the blood test done at earliest available appt, and a fasting test (you can have water), dont take any supplements either - if you take a b-complex containing biotin, stop for a couple of days before test as it can skew your results.

Thanks! It's a home finger prick test, so I'm in control of the timing! And I didn't know about the biotin until today....it's in my multi bone builder supplement!

If you havent done one before, drink plenty the day before so you are well hydrated, run your chosen hand under the hot tap (not too hot!) to encourage maximim blood flow, dont squeeze hard or you will damage the blood cells, I usually hold the chosen tip between forefinger and thumb and 'roll' it to encourage flow. It also helps to stick the finger where you can still see the puncture when it is inverted over the vial! Because TSH follows circadian rhythms to get highest reading try to do test by 9 at the latest.

Have fun 😁

Done one before, but there's some good advice re location of the puncture, as I got in a bit of a mess last time and bled everywhere!! πŸ˜‚πŸ˜‚

Lynneypin,

You don't need to skip your bedtime dose as long as there is 8 hours between last dose and blood draw.

Stourie
Stourie
in reply to Clutter

I thought that with ndt having so much t4 in it that 24 hours would be a better gap.

Jo xx

Clutter
Clutter
in reply to Stourie

Stourie,

A T3 dose can peak in the blood for several hours but is usually out of the blood in 6 hours so 8 hours is sufficient and the result will be a more accurate reflection of normal circulating T3 than leaving a 24 hour gap.

Stourie
Stourie
in reply to Clutter

Just googled the half life of t3 and 1 day is mentioned as is 2 1/2 days which I think is a bit much. I leave 24 hours between my last dose of t3 and blood test and I am usually near the top of the range and I certainly don't feel over medicated.

Jo xx

Clutter
Clutter
in reply to Stourie

Stourie,

T3 dose is in the blood up to six hours. After that it moves to the cells and will be out of the system within 3.5 days of last dose. If your FT3 is top of the range 24 hours after last dose it will be over range much of the time after your dose.

tiredthyroid.com/blog/2015/...

Stourie
Stourie
in reply to Clutter

We'll just have to agree to disagree.

Jo xx

Lynneypin
Lynneypin
in reply to Clutter

Thanks, having read your link I shall take my usual dose at night and test the following morning.

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