Changing from Levo to NDT

Going to give Thyroid S a go. I've read conflicting reports on whether to stop levo before starting something else. Some people have said stop the levo for 2 weeks prior to taking it, but I think I saw others had just stopped one and started on the other? And what dose do I need?

I'm currently on 150 Levo although was better on 175, reduced it but wasn't well so tried to increase and just couldn't.

All your advice gratefully received.

25 Replies

  • Mistydog, You can stop Levothyroxine one day and start NDT the next. It's usual to start with half a grain to see how well you tolerate the T3 in it and if good, increase NDT by half a grain every 2 weeks until you are on 2 grains which is equivalent to 150mcg-200mcg Levothyroxine. I'd be inclined to continue taking Levothyroxine, reducing dose by 50mcg for each half grain Thyoid-S added until you are on 1.5 grains.

  • Thank you, Clutter - that's very clear and I will do exactly what you say. Fingers crossed!

  • Oh, while I think about it, is it important to take away from food?

  • Mistydog, yes, away from food, medicines and supplements the same as Levothyroxine. When you are on 1 grain you can split the dose up to 12 hours apart if you feel an energy slump during the day. It's usually the T3 wearing off but you'll still have plenty of Levothyroxine sloshing around so may not experience a slump at all.

  • Chew the Thyroid S tabs.

    I don't entirely subscribe to the Levo = Thyroid S equivalence given as standard here. You may find that your steady state 'sweet spot' with Thyroid S is more than 2 'grains'. Although stopping the increases at 2 grains and seeing how you are would be very sensible.

  • Oh, thank you, humphrey. I didn't know you had to do that. I started them last night but will chew them tonight. Incidentally, I ordered them from <a website>, but they arrived from Thailand. I'm going to keep an eye on what happens.

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  • Yep - Thyroid S comes from Thailand, via <a website>, via <another website>, it all comes from Thailand. :-)

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  • Oops, sorry.

  • No need for you to apologise, Misty D - it's me that has transgressed.

    I do, indeed, apologise - I thought generic marketplaces were OK.

  • I think we both did!

  • The other day, I did not take my levothyroxine at bed-time as I had a blood test due in the morning. Silly me forgot to take my dose with me and had to go straight from blood draw to work. I thought nothing of it. By home time, I was feeling very tired and losing concentration.

    I am very well aware that was only a total of 48 hours between doses which would be very different to two weeks (or whatever else is recommended/suggested). Also well aware that many find that for a short period not taking levothyroxine, they might even feel better. But I ended up relating how I felt to this very question - and was in horror of idea of being without for two weeks. Two days was more than I ever want to experience again!

    Perhaps emotional rather than in any way scientific, but I am deeply concerned at the "stop levothyroxine for two weeks" approach. At the same time, we are all individuals and can react differently.

  • I agree, Helvella. I have occasionally forgotten to take the levo when I get out of routine, say on holiday, or something, and on day 3 I start to want to mass murder everyone, or myself! The thought of two weeks filled me with dread.

    I believe the idea is that it stays in the system for up to 4 weeks, but for me something definitely leaves my body within 48 hours.

  • I had never before felt as I did. Probably too tired to actually do anything terrible. There might be some in the system for some period - but that's a bit like saying there is water in the leaking tank. There is, but the level is continually dropping. :-)

    As I understand it, the Free T4 is in a form of dynamic equilibrium with the Total T4 so as Total T4 approaches zero, so too does Free T4. With obvious consequences on Free T3.

    (I'd be delighted if diogenes or anyone else can give a good account of exactly how the levels interact, especially at the unusually low levels we would see in those not taking any levothyroxine for extended periods.)

  • Rod and Misty, I do know that thyCa patients are taken off T4 for 4 weeks (although prescribed T3 for 2 of those weeks) in the expectation of TSH rising to >30 for uptake of RAI.

    It's often suggested Levothyroxine can remain in the system for up to 8 weeks, personally I found it took over 12 weeks to clear my system, but the amount remaining will be so small it won't help with symptoms. I've read that the exponential decrease means there is little useful Levothyroxine in your system 7/10 days after the last dose.

    I don't see any point in becoming hypothyroid for 2 weeks to switch from Levothyroxine T4 to NDT T4. As far as I'm aware, the only reason not to switch straight over to an equivalent dose of NDT is because of possible sensitivity to the T3 in NDT. Someone on T4+T3 combination should be able to switch to the equivalent NDT dose straight away.

  • I have read of some thyroid cancer patients having very bad experiences due to becoming severely hypothyroid. I hope I never have to do that.

  • Should we stop taking Levo on the evening before a morning blood test? I haven't done this in the past. Will my blood test results be skewed as a result?

    I too take my Levo in the evenings, 2 hours after any food. is this OK? I've had some pharmacists react stridently that it must be taken in the morning.

  • Yes it will skew your results, Adam.

    I take mine in the evening. Not a problem. Stops me giving in to the munchies too!

  • If you usually take levo in the morning and are having a blood test for thyroid hormones, you leave about 24 hours between the last dose and the blood test.

    If you take levo in the evening, you miss the evening dose and take levo after test in the morning. You can also take the evening dose as usual.

    The blood test should always be as early possible as the TSH is highest then.

  • Thank you mistydog and shaws. Very helpful. Will do this fir future blood tests. Interesting to note it's ok to take evening dose the following morning (after blood test) and still take same day evening dose. i had wondered about that.

  • Who is saying to stop Levo for 2 weeks before switching? Surely this is some sort of Thyroid Myth? Nobody needing regular thyroid meds could support that and function well. Not only is cold turkey A Bad Idea, but even after the 2 weeks the thyroidee has to build up dosage on the different med, which will take weeks. Sounds nuts.

  • See response from Glynisrose in this very thread.

    I too think it unlikely to be a sensible approach.

  • Levo is T4 alone and stays in your system for about 6 -8 weeks, I found it beneficial to stop the levo for two weeks prior to starting NDT.

  • The half life of T4 (natural or synthetic) is approximately 8 days in humans. This means that if you are on T4 and stop taking it, there will be half as much in your system on day 8 as there was when you started. It takes roughly 8 weeks before there is a negligible amount left.

    The half life of T3 is around 8 hours. So within 4 days there would be none left if you stopped suddenly. Fortunately, once in the cells it's effects last around 2 weeks!

  • I guess it all depends on what "negligible" means.

    I'd tend to think of it as meaning "too little to stand a chance of keeping you going". Whereas I can see that it could mean "too little to have any effect at all".

    The half-life values you see quoted are usually for healthy volunteers. Also, biochemical half-lives are not neat and well-behaved like those of radio-activity. So in a hypothyroid person, who is not continuing to take any levothyroxine, I'd hazard that the effective half-life will be shorter.

  • I agree, I would think you'd be on the floor after two weeks.

    But it takes 8 to disappear altogether - or at least to the point of being undectable.

    And it is all very approximate.

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