NDT and blood tests

[EmmaConstantine]

Hi everyone. I have been taking NDT around 6 weeks now, I had a fasting blood test done a week ago which showed my levels are now within range. However, what I find odd is that I was told to take my NDT 4 hours prior to getting the blood drawn, which I did. However I have since read that this is not correct and should not take it that morning until after having the blood drawn (but take it as normal the day before ) . I am still having some hypo symptoms although my blood work is saying I’m at optimised range!! Can someone shed any light on this and whether or not I should get another test done without taking my NDT beforehand. Thanks x

[Greybeard]

Hi Emma, the 4 hour instruction is quite common, it lets them know what is the maximum amount of hormone circulating in your blood stream. The problem from our point of view is that after the 4 hours our hormone levels continues to fall and we feel the effect as hypo symptoms. Most of us nod and smile sweetly and take our last dose of ndt 8 to 12 hours before the blood draw. We believe that this gives a more representative value for the amount of hormone in our systems.

Blood tests were designed for checking our levels when we are taking t4 only, they don't cope as well when taking t3 or ndt.

[fibrolinda]

Personally I would re test, taking last dose 8-12 hours before. I juggle day before dose taking it at 10pm so get 10 hour gap and always do the same.

[EmmaConstantine]

Thank you for your reply! So...in terms of re testing (which I obviously need to do ASAP) would you suggest taking my armour 12 hours before the fasting blood test ( i.e. the night before) or a whole 24 hours before?

[Jodiedebs55 in reply to EmmaConstantine]

I take armour and I wait 24 hours before taking the next dose so if I were having bloods drawn on a Tuesday I would take my usual dose of armour on Monday then have my bloods drawn at 9am Tuesday then take Tuesdays dose immediately after the bloods test it never fails that way

[EmmaConstantine in reply to Jodiedebs55]

Thank you for your advice! What dose are you on?

[Jodiedebs55 in reply to EmmaConstantine]

I take 2 x 1 grain of armour but just started taking a quarter of a grain at lunchtime armour works well for me 😁

[EmmaConstantine]

Sorry if you feel I missed your point...I’m new to all this and have only been taking armour for 6 weeks...I’m on 1 grain (60mg) and my blood results are now what my doc calls ‘optimal’ but clearly that’s because I took it 4 hours before. Thank you for your help

[SeasideSusie Remembering]

When booking thyroid tests, we advise:

* Book the first appointment of the morning. This is because TSH is highest early morning and lowers throughout the day. If we are looking for a diagnosis of hypothyroidism, or looking for an increase in dose or to avoid a reduction then we need TSH to be as high as possible.

* Fast overnight - have your evening meal/supper as normal the night before but delay breakfast on the day of the test and drink water only until after the blood draw. Eating may lower TSH, caffeine containing drinks affect TSH.

* Leave off Levo for 24 hours before blood draw, if taking NDT or T3 then leave that off for 8-12 hours. Take after the blood draw. Taking your dose too close to the blood draw will give false high results, leaving any longer gap will give false low results.

These are patient to patient tips which we don't discuss with doctors or phlebotomists.

As RFU says, her family leave 24 hours, virtually everyone else leaves the advised 8-12 hours gap. This is because the T3 element in NDT peaks within 2-4 hours after ingestion, and starts to leave the blood after 12 hours, so for most people leaving longer than a 12 hour gap gives a false low FT3 result.

[EmmaConstantine in reply to SeasideSusie]

Thank you what a wonderful response! You clearly know your stuff! I have been taking armour for 6 weeks now but this blood test that was taken 4 hours after taking the armour (even though fasted) has showed my results as ‘optimal’ ...even though I still have symptoms and don’t feel much different? I was advised to never take armour at night but if leaving a 12 hour gap I don’t think I would have much choice except to take at night?

[SeasideSusie Remembering in reply to EmmaConstantine]

Your results would have shown "optimal" because you took your NDT just 4 hours before the test, so your hormone levels would have just reached their peak. The results didn't show your normal circulating hormone level, which will be lower and this is probably why you still have symptoms.

I take a combination of synthetic levo and T3, and what I do the day before my test is to split my dose (I normally take it all in one go) so that I get the timing right to show the normal circulating hormone level. What you could do is alter the timing of your NDT the day before, either take it 8-12 hours before you know you're having your blood draw if you take it all in one dose, or split it and take half in the morning, and half at bedtime (depending on time of blood draw).

[EmmaConstantine in reply to SeasideSusie]

My test will be at 9am. The day before should I take half first thing in the morning then half at around 10pm before bed? Or not take it at all that day until 10pm when I take the whole tablet?

[SeasideSusie Remembering in reply to EmmaConstantine]

It's up to you whether you split your dose or not. If you split your dose then your FT4/FT3 will be lower than if you take a full dose at 10pm.

[EmmaConstantine in reply to SeasideSusie]

In that case surely it’s best to split it?

[SeasideSusie Remembering in reply to EmmaConstantine]

I split mine, as I mentioned. But whatever you do, make sure all your blood tests in future are done under the same circumstances so that you can compare them accurately.

[EmmaConstantine in reply to SeasideSusie]

Thank you so much and I will do x

[EmmaConstantine]

Thank you for your reply. I think I’m going to split the dose in half the day before and take the second half around 12 hours before the blood test