Thyroid UK
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Switching from synthetic to natural

On the NatureThroid site is stated: "Due to the higher bioactivity of natural thyroid, physicians may choose a slightly lower dosage to achieve similar results for patients converting from synthetic thyroid." I'm wondering whether this is because of the higher proportion of T3?? Pigs make more T3 than humans do so that natural products aren't quite the right proportion.

Those of you who have switched to the natural, how did you determine how many grains to take? Do any of you supplement with extra synthetic T4? Did it take you very long to adjust to the change?



5 Replies

I think the official conversion charts often state that 1 grain is equivalent to 100mcg of thyroxine but I believe that 1 grain is more equivalent to 75mcg of thyroxine. One grain contains 38mcg of thyroxine and 9mcg of T3 (which is said to be roughly 4 times more potent thant T4). So 1 grain = 38mcg + (9 * 4 = 36mcg). 38mcg +36mcg = 74mcg of thyroxine.

I think the STTM book and website recommend starting on half a grain and then increasing by half a grain every 2-3 weeks until you get to 2 grains when it is better to increase every 4-6 weeks. However it has taken me nearly a year to increase to 2 grains, but that is because I seem to be very sensitive to meds/changes in dosage :D xx


I just switched directly from levo to dessicated and this link if you look at the bottom gives you the equivalent dosage of different ones.

You could also start on a smaller dose if you wish and then increase upwards gradually.

This is a link which may give you the info you require.


Thanks for your answers! I was previously on 75 mcg Synthroid plus 5mcg Cytomel. Every several weeks it would seem that my hypothyroid symptoms would return. (I am thyroidless.)Anyway, I decided (with the help of an alternative physician) to try NatureThroid. First I began with one grain plus 38 mcg Synthroid, no Cytomel. Then I switched to no Synthroid/Cytomel and 1 1/2 grains. Next to no Synthroid/Cytomel and 2 grains. Two grains was too much for me. I think that the one grain plus some Synthroid might be the solution.

Have any of you read "Gail's Thyroid Tips"? She states that there is nothing wrong with combining the different thyroid medications. I guess it's all so individual and very frustrating.

From what I've read, it does seems that patients on natural dessicated thyroid hormone need a higher dosage. I have read that anywhere between 3 and 5 grains is the norm, which seems high to me. I'm sure size and age are factors as well.

Any comments?!

1 like

Yes I think some people do well on a mixture of synthetic T4 and NDT and some with T3 and NDT.

I think STTM say most people need between 3 and 5 grains and the late great Dr Lowe (RIP)said 2-4 grains. I have just gone up to 2 grains myself :) xx


I was on 125 mg levo and switched to 2.5 x 60mg NDT - i cannot recall exactly how much t3/t4 they contain. The first couple of months i felt awful while i was phasing out levo and phasing in ndt - i didnt really know what i was doing and it's likely i was getting in too much t4.

Anyhow, when my symptoms eased, i stayed on that dose. It took me several months. I'm so pleased i did it. I will NEVER let an NHS GP control me again and relegate me to a half life by ignoring my symptoms and keeping me undermedicated , being concerned only with ticking boxes.


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