Changing to NDT...contradicting advice?

Hi, I'm waiting on my delivery of Thyroid-S. I was reading up on how best to make the switch, and how to be successful with NDT. Someone here suggested on another thread that you can just switch over, I assume that means one day I take the last levo and then the next start NDT? Then I've read elsewhere I'll need to stay off levo for at least a week, supplement with ferritin and selenium. But then! I've also read that taking iron supplements can bind with NDT and make it unusable??

Also, when reading here about taking Thyroid-S, people say begin with 1 grain, move up in quarters, but pretty sure Thyroid-S is tablets? Should I buy a pill cutter and cut them in 4?

Thanks all!

15 Replies

  • Welcome to the forum, Polomint2.

    How much Levothyroxine are you taking?

  • I'm taking 75mg at the moment, and my last TSH came up at 1.45 and FT4 17.1

  • Polomint, 1 grain NDT is bioactively equivalent to 75mcg Levothyroxine so you can switch straight over. Most people split NDT into 2 doses to even out the T3 peaks so buy a pillcutter and halve the tablets. You can increase by 1/2 grain after two weeks if you need to but increase in 1/4 grain increments after at 2 week intervals to avoid overshooting your 'sweet spot'. I recommend you have a thyroid test, including FT3, six weeks after you've been taking 2 grains before increasing further to check FT3 remains within range.

    Iron should be taken 4 hours away from Levothyroxine, T3 and NDT as it binds with thyroid replacement and reduces aborption and uptake.

  • I didn't take my dose last night because I thought I'd have to leave it a while :( So 1 tablet is just called a grain? I don't know if my doctor will do a FT3 test, I've heard it's hard to get done. Should I inform her I've started taking NDT, and hope she'll monitor me? Thanks for your help

  • Polomint, NDT is combined Levothyroxine and T3 so there's no need to clear Levothyroxine first. Take your dose tonight as usual and switch to Thyroid-S the morning after.

    NDT was historically administered in grains and the terminology persists. 1 grain NDT is usually a 60 mg or 65mg tablet containing 38mcg Levothyroxine and 9 mcg T3. Thyroid-S comes in 1 grain tablets.

    See how you do on Thyroid-S before informing your GP and asking her to monitor you. Even if your GP agrees to order a FT3 test NHS labs usually decline to analyse unless TSH is <0.03. You can order private thyroid tests from Blue Horizon and Genova via

  • I suggest you don't take the last levothyroxine!

    Far better to have a reasonable quantity of levothyroxine available so that, if it doesn't work out at first go, you can revert to levothyroxine. (Maybe I am being over-literal, but a point worth thinking through, I feel.)

    You simply must keep iron four hours, or more, away from thyroid hormone. It doesn't mean you can't take it at all.

    (As I do not take desiccated thyroid, I'll leave others to say more.)

  • I'm due a refill soon anyway :)

  • I would not bother to tell your gp just keep collecting scripts for levothyroxine or you might find you need it and the gp wont prescribe it

    When it comes to tests your gp wont know any difference

    Just be very sure never to take the ndt in the 24 hours before the test and have the test early morning , fasting and only water to drink

  • My god hopefully I'll end up with cupboards full of levothyroxine...........because I'm really hoping NDT is gonna fix my irritability and energy. My relationship with boyfriend and son can't take anymore :(

  • Polomint, it's wasting NHS money if you collect Levothyroxine you don't intend using. Make sure you have some Levothyroxine in case you can't get NDT but you should make an arrangement to collect scripts without getting them dispensed.

  • I Oh I thought I'd have to collect it too or doctor would cancel.

  • RFU, the test results might cause the GP some consternation with suppressed TSH, lower, possibly suppressed FT4 and high FT3.

  • Maybe maybe not because they only do TSH and many GPs are so ignorant of thyroid

  • RFU, Polomint's practice tests TSH and FT4 so it may be noticed.

  • well if she is only tested once a year maybe its best to not take NDT for more than 24 hours maybe 48 or even 72 hours

    but yes whatever she does she needs to continue collecting the scripts for levo otherwise they will even refuse to prescribe it

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