TSH and FT4 levels on NDT?

I have been taking Thyroid-S for over a year, after finding that neither Armour nor Erfa worked optimally for me (I was first put on Armour, then on Erfa after it allegedly changed somehow, too).

On Thyroid-S, I feel stable, the way I guess you are supposed to feel when on NDT (or any other thyroid drug, for that matter). On Armour, I felt slightly under medicated regardless of dose and, on Erfa, it was constantly up and down.

My labs eight months ago (on Thyroid-S) looked like follows: TSH <0.01 mUI/L (0.35-4.5), FT4 0.8 ng/dL (0.7-1.5), FT3 2.9 pg/mL (1.7-3.7). I take Thyroid-S once a day, in the morning, and always go to the lab 24 h after taking it.

Although I felt good, I suspected maybe my FT4 levels were suboptimal, so I added another grain daily. I just got my latest lab results back:

TSH <0.01, FT4 1.2 (0.7-1.5), FT3 4.6 (1.7-3.7). So FT4 midrange, and FT3 levels out of range, 24 h after taking the pills.

I am not sure how 1 more grain of NDT (=9 mcg of T3) can make such a difference when it comes to FT3 levels 24 h after taking NDT? I have always been a poor converter, so I am not sure the higher FT4 levels have anything to do with it.

I cannot say I feel overmedicated, but I guess I should reduce my current dose to bring my FT3 levels in range (since they were out of range 24 h after taking any meds, I guess they were ca 20% higher on the day before?) This should also mean that, eight months ago, when my FT3 levels were midrange 24 h after taking Thyroid-S, they were about 20% higher 24 h earlier, so around 3.2 (ref 1.7-3.7)?

I have been considering trying another brand of Thai NDT, but I am not sure I should give up on Thyroid-S if I feel good on it? Another idea would be to add half a grain daily to see if I can get my FT3 levels up slightly...not sure how much FT4 levels matter on NDT?

I seem unable to get my FT4 midrange and keep my FT3 levels in range at all times, at least on Thyroid-S, but wonder if there is such a thing as "ideal free Ts" when on NDT?

22 Replies


FT4 is usually quite low when taking NDT and it really doesn't matter as long as FT3 is good ie in the upper third of range. If you feel good on Thyroid-S I don't understand why you want to change the brand or the dose. If it ain't broke don't fix it is a good maxim.

If you are going to alter dose 1/4 grain increments are more sensible when you are close to optimal dose as that will enable you to avoid over shooting.

Thanks a lot, Clutter! I was wondering if FT3 2.9 is OK (probably around 3.2 on previous day if ca 20% higher) when ref ranges are 1.7-3.7...I agree 1/4 grain increments would be more sensible. The pills are tiny but using a pill cutter splitting them should be fairly easy. Thanks again:-)


You said you feel fine so 2.9 is fine. How you feel is much more important than where in range your blood result is.

If you left 24 hours between your last dose and the blood test, then that FT3 is a false low, meaning that the true figure is even further over the top of the range. So, you are over-medicated. You should only leave 12 hours, because NDT contains T3. 24 hours is for T4 only.

I admit I find the info about NDT a bit confusing, because many claim the hormones in NDT are released more slowly than the hormones in synthetic drugs, especially synthetic T3, because the hormones in NDT are attached to binding protein...so you normally only have to take NDT once a day, unlike synthetic T3 which needs to be multi dosed to spread out the effects of direct T3. I have only taken NDT once daily so I don't know if there would be any advantage to taking it twice daily instead, leaving say 12 hours between doses...?

Well, I'm not really the one to ask, because NDT wasn't good for me however I took it! I tried taking it all at once - that's how Dalle told me to take it - and I tried taking it in split doses. But, NDT just wasn't for me, it made me very ill. T3, on the other hand, I find is better for me if I take it all in one go.

I really don't know if there's any definitive answer, I think it comes down to individual preference, and we just have to keep trying different things to find what works for us - no matter what the theory!

I agree! Would you - or anyone else - agree that you should assume your FT3 levels were +/- 20% higher 24 hours earlier, provided you take meds containing T3 once a day, before having labs done? Or does the 20% figure apply to NDT or T3 taken 12 hours before going to the lab...meaning FT3 levels could be up to 40% higher if you leave 24 h between taking meds and having labs...? I realise this sounds rather confused, but hope you know what I mean.

Well, I'm not terribly sure what you mean, so I don't have an answer to that. I hope someone else does! :)

Splitting T3/NDT 2/3x a day is the way to go . It's much better for the adrenals too it doesn't put so much stress on them .

Now I'd be be very interested in hearing from as many members on NDT as possible: do you take it once a day, or twice daily or even more? The advice is very confusing; most doctors prescribing it recommend taking it once a day (in the morning), and the Belgian doctors on NDT that I know of take it that way as well...but many patient groups recommend splitting the dose. I'd be interested in hearing about other people's experiences, especially if you've taken NDT both once and several times daily. Did you notice a difference?

I have read about splitting doses putting less strain on the adrenals, but thought that applied more to synthetic T3 than NDT...?

It's always recommended to split the T3/NDT . You can split 2/3 x/day . I split it now 2x/day eight hours apart or more . And run labs just before my next dose to see my trough (lowest ).

Well, the Hertoghe doctors in Belgium (which is where I go for treatment) don't seem to recommend splitting the NDT dose...which is why I find the advice both contradictory and confusing. On Thyroid-S, which is the the NDT drug I've been on for the past 18 months and that is working really well, I don't feel the need to split the dose...at least I don't get a racing heart or increased sweating or any similar symptoms when taking the dose in one go in the morning.

From a purely practical point of view, taking NDT more than twice daily would simply be too inconvenient for me...twice a day would be possible if really recommended but, so far, I have not seen any "evidence" compelling enough to convince me to switch to multi dosing...

I have tried both ways & find once a day better for me.I also used to forget to take second dose quite often which was why I tried once a day.As I said it works fine for me but we are all different & have to try both ways of dosing to see which works best.

I agree. I have taken NDT once daily for quite some time and feel good that way...like you say, I imagine it's easier to forget taking the second dose if you split them. I also take no other drug twice daily which could possibly make it easier to remember...Also, I am not sure that taking T3 close to bedtime would agree with me...but, like you say, we're all different! However, it's nice to know that some users take NDT once a day and feel fine that way:-)

I read some time ago that the hormones in NDT (unlike the hormones in synthetic drugs) are bound to proteins, making them release more slowly into the bloodstream...I have no way of knowing if this is indeed true, but I do know that I don't seem to have any problems taking NDT once daily...however, every time I see conflicting advice, I start asking myself if indeed I'm doing the right thing...!

I repeat, it's not the way for everyone. We're all different, and saying that everyone should do everything the same way is what endos do. And we know how wrong they are!


I am doing a private blood test tomorrow and I take one grain NDT. am. and half grain early evening, I usually leave the evening dose off when doing blood test, but wonder if it is best to take it this evening around 8.30 pm. and do blood test 8.30 am tomorrow, so I am leaving 12 hours, or should I not take my NDT dose this evening.

I am doing the test for my own information, to see what my levels are, as I am not feeling very well lately. I also have had a virus for about two months and cannot fight it off and wonder if my levels are out and this is why the virus is lingering.

Any advice is really appreciated.

I think you should take your evening dose at 8.30 pm, and do the test at 8.30 am. That would be perfect. :)

Many thanks greygoose,

I will do that.

Best wishes.

You're welcome. :)

when using NDT you need to ignore results you treat on symptoms and body temoerature

T4 is irrelevant and if youfeel well with a higher t3 thats fine

my lot have tried Thiroid but do not like it or do well on it wheras on thyroid-s they are fine

so i would stick with what your doing

Thanks:-) Yes, I really like Thyroid-S. At first, the fillers made me wary, but it really seems to be working so I am sticking with it. It's also much cheaper than Armour and Erfa, neither of which worked optimally for me, BTW.

This is really interesting thought. I have low energy yet t3 makes me hot.

You may also like...