Thyroid UK
90,417 members104,778 posts

T4 conversion block and starting NDT

I think I have a build up of T4, and not converting effectively to T3.

7th Feb results

TSH 3.78 (0.27-4.2)

T4 17.5 (12-22)

T3 3.5 (3.1-6.8)

Had been on 75mg levo raised recently to 100mg.

Started feeling progressively unwell from around the 7th Feb.

With abdominal pains, chronic diarrhoea, lightheaded, dizzy, trembling, some palpitations and a few chest pains. I also noted that my temp began to raise and at first thought that I had an infection.

Stopped levo last Friday in anticipation of NDT arrival and because I was convinced that it was making me unwell.

How long shall I wait for the levo half life to leave me before starting on new meds?

Am still feeling unwell...

Any advice hugely appreciated.

11 Replies

I think it's very unlikely you had a build up of T4 - you're actually undermedicated according to those results. But some people do find that levo makes them feel worse, not better. That could be because you weren't on enough (which you clearly weren't) or because you're intolerant to some of the fillers in your brand of tablet. Or that you have nutritional deficiencies - low Vit D, low Vit B12 and in particular, low ferritin. Research suggests that you need a good level of iron to convert T4 to T3. Also that selenium supplementation helps.

Mostly here we don't recommend coming off levo before starting NDT - there's no need as you can just switch from one to another. No wonder you're feeling poorly.

When your NDT arrives, as you've already been on 75mcg levo you can start on one grain a day, no need to split the dose. After a fortnight you can try raising to 1.5 grains a day if you feel you need to, then a fortnight later another half grain if you feel you need it. We recommend sticking with 2 grains for several weeks before raising again because it can take time for the thyroid hormone to accumulate in your system and you may not need more.


Thanks jazzw, I thought I had to wait a while as I feel so poisoned, and had read about the half life I didn't want to exacerbate the situation and just pile more T4 on to the existing T4. It really is confusing.

I have the NDT so I'll start in the morning. Is it the same principle as levo in to take an hour before food?

Also can I split the grains or do I need to buy 1/2 grain dose?


Yes, same principle - take well away from food. You could even start today - it wouldn't hurt, especially as you've been off Levo for nearly a week. Doesn't have to be taken in the morning.

You can break the tablets in half but I honestly wouldn't start with half a grain - I'd start at a grain.

But I understand you might be feeling nervous, so do what makes you feel comfortable. There's no magic involved - it's just thyroid hormones.

Hope you're feeling better very soon.

1 like

You ar very underdosed and Jazzw is correct in that you can switch from one thyroid hormone replacement to another without stopping. You are also seriously undermedicated with a high TSH.

I am sure you will feel much better with NDT and I'll give you a link which may be helpful:-

1 like

Thanks shaws.

Thanks for the link.

Do you have any idea about how many grains I may need?


Also any ideas as to how long it will it take to start feeling better?


I started feeling better within a few days - the T3 was definitely something I needed. Sounds silly but the first thing I noticed was that I could lift my arms above my head and they didn't feel so heavy!

1 like

I'm very much looking forward to feeling well...I know it's possible from forums like these, but am also wary that it's all very complicated to find the right meds...and the right doctors...

1 like

Everyone is different unfortunately. What you have to do is concentrate on how you feel on a particular dose and keep to that dose for at least two weeks. The 'effect' of 1 grain of NDT is around 100mcg of levo.


Ok thanks : )


Hi, just to update...I started on one grain of NDT on Thursday afternoon and within an hour felt that the abdominal pains were much less painful the cramping stopped and the following morning had a 'normalish' bowel movement, the first for almost a month. It's early days and I know that I'm not going to regain my health overnight but it felt like a mini miracle, as have been feeling terrible with all the stomach pains, cramping and chronic diarrhoea.

I am still experiencing some discomfort in my abdomen but normalish bowel movements have completely returned, I'm sure that when I introduce another half grain that I will feel even better.

I just can't believe how quickly my body responded.


You may also like...