Blood tests on NDT & Thyroxine: So I have now... - Thyroid UK

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Blood tests on NDT & Thyroxine

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22 Replies

So I have now been taking 100mg Thyroxine & 1 grain of Thyroid-S for 2 weeks and I feel good. I am going to test my bloods in a month. So do I take my Thyroxine 24 hours before the test & NDT 12 hours before to get an accurate result?

I will have my bloods taken at 8.35am after fasting.

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22 Replies
SeasideSusie profile image
SeasideSusieRemembering

Yes, last dose of Levo is 24 hours before the test and last dose of NDT is 8-12 hours before test.

fixit profile image
fixit in reply to SeasideSusie

That is what I thought. Thank you x

DoeStewart profile image
DoeStewart

Can I ask what sort of results you would expect from taking thyroid s with 100 Levo? What difference has it made to you? I take 100 Levo and am struggling, being dosed by TSH. Are you self medicating?

fixit profile image
fixit in reply to DoeStewart

I am self medicating and have recently swapped from years of 3 grains of NDT as although I felt well on it I continually ran hot & felt overheated. I was wondering if it was too much NDT for me. It is early days & Im waiting to see how I settle on this dose but so far I feel much better. I am hoping my FT4 will now rise.

DoeStewart profile image
DoeStewart in reply to fixit

Thank you for your replying- have you told your GP about tak ing thyroid s? I get 100 Levo on script, I have had private blood tests with Medichecks, full thyroid plus vitamins and posted these on this forum. I received great support and advice about low vitamins which I have supplemented. I obviously have to have my yearly bloods done at GP practice, just TSH and T4. My TSH is always under range but T4 is in range - I have a constant battle about reducing my Levo. I have thought about Thyroid S but wondered how I would explain my results to Doctor?

Batty1 profile image
Batty1 in reply to DoeStewart

I had same issue with low TSH and below range T4 and because TSH was low my meds would get reduced and every 8 weeks it would be a rinse and repeat as the dose change never raised my TSH and my T4 stayed below or low in range after a while I told Endo NO to reducing my meds because at this rate I will be on no meds without a thyroid.

Lots of medications can make thyroid numbers crazy for me it's immunosuppressive therapy and Cymbalta for chronic pain (cymbalta) was huge once I stopped my next labs my TSH went up but my T4 is below range.

DoeStewart profile image
DoeStewart in reply to Batty1

Hi Batty1 - that's exactly it, the Dr only looks at TSH which seems ridiculous when I've had just about all my thyroid gland removed over 30 years ago? When I suggest a 25mg increase you'd think I'd asked for some illegal substance on prescription. They look at me in horror as my TSH isn't in range?

fixit profile image
fixit in reply to DoeStewart

My GP knows & self medicate & I do my own bloods tests & but my own meds.

I know it's not usually recommended, but I only take NDT once (in the morning) and always have labs 24 hours after taking it without any problems. The only thing you need to be aware of is that your FT3 levels can be falsely low so you should assume they were 20-25% higher the previous day.

DoeStewart profile image
DoeStewart in reply to

Hi Cat68 - thanks for that info. I am sorry if I sound dumb but trying to just understand it a bit more. Does the NDT lower your TSH? How long does it stay in your system? If I was taking Thyroid S for instance along with my prescribed Levo and was due GP yearly bloods, could I stop.the Thyroid S and bloods would only show results for Levo?

in reply to DoeStewart

Yes, NDT often lowers or even suppresses your TSH because it contains T3.

How long does NDT stay in your system? Well, it contains T3 and T4. T4 has a half-life of about one week. T3 has a shorter half-life which is why FT3 levels will decline faster than T4 levels.

DoeStewart profile image
DoeStewart in reply to

Ok thank you for that. I am seriously considering adding a bit of ndt to my Levo as Dr will not give me an increase and actually wants me to drop from 100 to 75. I have in the past been on 175 ? 7/8ths thyroidectomy over 30 years ago so struggling on such a low dose of Levo.

DoeStewart profile image
DoeStewart in reply to

If my GP never tests my T3 then that wouldn't matter but I'm guessing it would further reduce my TSH?

in reply to DoeStewart

Yes, which is a problem if your doctor is TSH obsessed (many doctors are).

If I understand you correctly, you only have a fraction of your thyroid left? In that case, no wonder you feel bad on a low dose of levo, especially if you are a poor converter as that leaves you both T4 AND T3 deficient.

Ideally, you should try to get symptom-free instead of dosing by the TSH. Many people need FTs in the upper third of range to achieve that, while others feel well with low FT4 and high FT3 levels or the other way around. It's highly individual, but if you are still symptomatic, it's safe to assume you are not a high enough dose.

in reply to

To try to give you an idea:

At my lab, the reference ranges for FTs are:

FT4 0.7-1.5

FT3 1.2-3.2

In order to feel fine and remain symptom-free, I need my FT4 to be at least 1.1, and my FT3 to be at least 2.7 (I leave 24 h between taking NDT and going to the lab so it's around 20% the previous day which puts it at the top of range).

That's just me, but I understand from this and other forums that I'm not unique.

My TSH has been suppressed (<0.01) for years and never has had anything to do with how I felt. I have Hashimoto's and, while on T4 only for 10 years, had very low FT3 so I'm a poor converter.

I take 4 grains of NDT daily.

DoeStewart profile image
DoeStewart in reply to

My last Medichecks was February 2019

TSH 0.183 ( 0.27 - 4.2)

Free T3 4.41 ( 3.1 - 6.8)

Free T4 16.2 ( 12 - 22)

I had GP tests done in September 2019

TSH 0.11 (0.30 - 5.50)

T4 18.2 (11.5 - 22.7)

All on 100mg Levo.

in reply to DoeStewart

Well, your latest FT4 levels look good, but that doesn't tell us much because we need to know how well you are converting it to T3. The only way to find out is to have your FT3 levels measured at the same time.

Although most conventional doctors disagree, the TSH on its own is going to tell us very little if anything once on thyroid hormone replacement, so you need to go by the free Ts, especially the FT3 since T3 is the active thyroid hormone....along with symptoms. So far, I don't think I've "met" anyone (online) who was on thyroid hormone replacement, completely symptom-free and able to live a normal life, where the only thing that counted was an in range TSH.

DoeStewart profile image
DoeStewart in reply to

I agree but my GP doesn't see the need to test T3- as long as TSH is in range then all is right with the world !!. I don't understand why my T4 is higher on GP blood test than on Medichecks, not much difference in ranges and no difference in my dose of Levo?

kmf0503 profile image
kmf0503

I was on Naturethroid for 10 years and also did not spilt my dose and tested after 24hours. I didn't know to do anything differently. My lab results were also consistent and I am also a poor converter.

DoeStewart profile image
DoeStewart in reply to kmf0503

I wish I had the courage to do something. I know I can't carry on like this, my hair is half as thick as it was, I'm washing it off my hands when I'm washing my hair. Can't lose any weight even though I try and keep busy, aches and pains in joints. I think my GP will cross me off the books if I self medicate.

kmf0503 profile image
kmf0503

I have the same story with my hair....even with lab work that looks fine. However, I seem to be losing it more rapidly since coming off NDT and going on levo/t3 combo. I wish I had an answer for you. :(

fixit profile image
fixit in reply to kmf0503

Sorry to hear that. I’m hoping my will improve with more T4.

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