Pharmaceutical Equivalency of Levothyroxine (T4), Liothyronine (T3) and Natural Desiccated Thyroid (NDT)

I have worked with thousands of thyroid patients over the past fifteen years. In my Recovering with T3 book back in 2011, when the first edition was released, I made it very clear that I believed that it took between 40 and 80 mcg of Liothyronine (T3) to correct hypothyroidism in most thyroid patients who were using T3-Only. A few patients may need a little less and some need more than this. This was based on endocrinology texts and also on a lot of my experience with working with thyroid patients who needed to use T3 in order to recover from hypothyroidism. I still stand by this view.

Here is an article by Dr Tania S Smith of Thyroid Patients Canada. The article refers to various studies that suggest a typical replacement dose of T3 that is very close to the 40 – 80 mcg range that I have mentioned. One study that Dr Smith cites concludes that a full replacement dose of T3 is 50 – 100 mcg, and another concludes that 50 – 120 is required to achieve a euthyroid state. These numbers are totally consistent with the information that I provide in my Recovering with T3 book.

The title of the article, and much of the content, is about the equivalency of T3 to T4 medication. It is clear from the research studies that there is not a fixed mathematical equivalence. We are not robots, and as human beings we vary considerably in our ability to convert from T4 to T3. However, the past studies referred to suggest that in many cases it requires 25 – 35 mcg of T3 to replace 100 mcg of T4 medication. There will of course be some people that might need more or less T3. In all cases, only the use of the patient’s clinical presentation (symptoms and signs) would actually reveal if the individual is on the correct dosage and is effectively euthyroid.

I thought the article was very well written and interesting. I think that you will too.

Here is the link:

In a recent blog post I have discussed why multi-dosing with T3 is the most effective and safest way to deliver the total daily dose of T3 medication. I include this link because it is so relevant to this post. The two articles form a useful pair of blog posts. Together, they cover:
1) How much T3 is usually required to provide a full replacement T3 dose (this blog post).
2) Why 3-4 multi-doses of T3 is often the best way for thyroid patients to take that full replacement dose of T3.

Here is the link to the blog post on multi-dosing of T3:

Best wishes,


Paul Robinson

Paul Robinson is a British author and thyroid patient advocate. The focus of his books and work is on helping patients recover from hypothyroidism. Paul has accumulated a wealth of knowledge on thyroid and adrenal dysfunction and their treatment. His three books cover all of this.

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