Switched from T4+T3 to NDT now feeling hypo - Thyroid UK

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Switched from T4+T3 to NDT now feeling hypo


Hi all, I've been on 150mcg T4 + 10mcg T3 for a year now, and a week ago was switched to NDT (2 grains). Four days in and I started to feel really hypo (terrible fatigue, sleeping 12 hours a night, freezing cold and headaches). Is this normal, and how long should it take to see an improvement? I'm due to have bloods done after 3 weeks, but hoping I don't have to feel terrible until then. Has anyone else experienced this when switching? Thanks in advance :)

20 Replies

Hi there .....2 grains of NDT is not the equivalent of your T4/T3 combo that you were taken.....it is less,so may be why you are feeling unwell.Perhaps someone else will advise.

I have just transferred onto Armour Thyroid ( buying myself but Endo monitoring me)

I had been using it for 3weeks when I told him I was doing so and he said that was not long enough and has told me that my trial needs to be for 3 months......plus vitDand B12.Then I will have blood tests and see him again in November.

However I started on 1 1/4 grains and this morning have increased to 1 1/2.

I am older and taking it carefully .....so far so good!!

kez01 in reply to Hidden

Thanks so much for your reply :) I didn't think it was quite enough, but the doc wanted to be conservative to start with. I take vitD and B12 too, but after 20 years on T4 only my poor thyroid is pretty shot. New doc is great so I'm hopeful this is just a hiccup and I'll finally be able to get things on an even keel. Good luck with your switch!

Hidden in reply to kez01

Thanks kez01......I have certainly noticed a difference.....bloated stomach gone ...legs getting better and feeling generally much happier.

I think we all want instant improvement don't we? It's such a long journey trying to get things right. However,having tried most routes I had to try NDT.I needed to see what would happen if I got rid of T4/T3 out of my body.The first two days were not good .......headachy like a withdrawal symptom....but each day now I am improving.

Best wishes to you too and hope you eventually find your optimal level.


Hello kez01,

Welcome to our forum and sorry to hear you are having problems.

I don't medicate on NDT but understand a switch over can sometimes be difficult. Raising the dose must be quick enough not to activate Hashimoto antibodies if you are a sufferer but slow enough to allow your body to tolerate the changes.

Low iron and high or low cortisol issues can make the body intolerate of accepting enough NDT to feel well but you are in early days so have plenty if oppotunity for adjustments which I'm sure more experienced users of NDT will advise you of.

If you are still on a too low dose of NDT as Marfit74 has advised, is it possible to supplement with a bit of T4 until you raise? This is not advice as I really don't know but just a suggestion.

You may find this link useful


Hope you feel better soon,


Hidden in reply to Hidden

Yes I have been consulting my Stop the Thyroid Madness book and have found it helpful and it is giving me confidence....so can recommend it.x

Personally I think that, to know exactly what the equivalence is between two regimens of treatment (i.e. switching between T4 or T3 products, or between different regimens of T3/T4 versus NDT etc) it's essential to test for TSH, FT4 and FT3 before switching and again immediately afterward. In the simple case of T4 only treatment it's well known that different brands of pills show different bioavailability for the same dose. How much more likely is this for more complicated switching. Getting accurate data for switching outcomes is a cardinal rule for best results.

shawsAdministrator in reply to diogenes

Thanks - I have copied your advice if I need for future use. It's important to have a base to start from when changing hormones.

Hidden in reply to diogenes

Yes,my blood tests before seeing my Endo showed 2 low results which is why I told him what I had been doing.Now I have created myself a list of Armour equivalents to T4/ T3 dosages,to guide myself by.

1grain ,1 1/4, 1 1/2,1 3/4, up to 2grains.....which I hope I won't need to go above.

We could all do with an "Ology " getting ourselves sorted ....couldn't we?

I'm a bit confused with the equivalent between Levo and NDT. I was on 100mcg of Levo but have just started with Armour 60mg 1 grain, which I'm taking in 2 halves (morning and lunch). First day in so no effects to report as yet.

Clutter in reply to ColinK

Thor1956, The manufacturer claims the 1 grain is bioequivalent to 100mcg Levothyroxine. It's probably closer to 75mcg. You'll probably need to increase to 1.5 grains in 2 weeks.

Hidden in reply to Clutter

Yes,I am working on 1grain being nearer to 75mcgs........

38 mcgs T4 and 9mcgsx4 T3 = 36 totalling 74. T3x4 is as stated in Armour Thyroid Patient leaflet.

Therefore 1 1/4 grains = 92.5. 1 1/2 grains = 111

Will welcome comments if anyone thinks I'm wrong .

Clutter in reply to Hidden

Marfit, NDT manufacturers claim T3 to be slightly more than 4 x stronger than T4, the link below says it is 3 x stronger.


The difference is negligible +/- 9mcg T4 at 1 grain.

Kez01, 2 grains NDT contains 76mcg T4 + 18mcg T3 equivalent to 130mcg T4. 150mcg T4 + 10mcg T3 is equivalent to 180mcg T4.

kez01 in reply to Clutter

Thanks For clarifying Clutter

kez01 in reply to kez01

Oops, meant to ask whether you'd recommend an increase? Hoping to avoid a two week crash before my next bloods.

Clutter in reply to kez01

Kez01, if you feel undermedicated increase by half a grain.

Hidden in reply to Clutter

Clutter.......I'mtotally confused now.

My Armour Thyroid patient leaflet clearly states that the T3 Liothyronine is approximately 4 times stronger than T4.

Am I wrong in thinking then that 1grain = 38 mcgsT4 + 9 T3 x4 = 74 mcgs which would make 2grains = 148 mcgs.

I used to multiply the MP by Liothyronine x3 but interpreted that the T3 in Armour being natural is stronger and that is why they say it is 4 times stronger.

It seems as though I should adjust my thinking ?

Clutter in reply to Hidden

Marfit, there's no difference between the strength of synthetic T3 or the T3 in NDT. T3 is either 4 x stronger than T4 as the manufacturer claims or it is 3 x stronger as the research claims. Based on the manufacturer's claim of 4 x stronger your maths is correct.

Hidden in reply to Clutter

Thanks for that Clutter......I must admit I was a bit worried that my Armour dose was not up to the previous T4/T3 combo which wouldn't have made sense.

Clutter, many thanks. I'm full of positive apprehension and really hope it sorts my problems/symptoms.

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