Pro tip: Substitute T4 for T3 in a combination therapy

Nowadays combined T3 and T4 therapies are often prescribed to mimic the normal function of the thyroid glands, people who undergo these therapies obtain a significant improvement in their quality of life compared to the previous situation, but there is a way to improve even more the well-being sensation.

As it can be seen in the publication of the New England Journal of Medicine of 1999, in the article by Bunevicius et al. , the replacement of part of the T4 in therapies with a high amount of it (doses greater than 50mcg per day of T4) by T3 caused a large number of improvements in patients such as:

  • Greater energy.
  • Better concentration.
  • An improvement in well-being.
  • Reduction of side effects such as: dizziness, heat, chills, blurred vision and nausea among others.


  • The protocol consists of reducing the dose of T4 by 50mcg and replacing it with 12.5mcg of T3.
  • As we can see the reduction is given in a percentage of 4:1 therefore to avoid possible side effects I would recommend gradually decreasing the dose of T4 by 4mcg for each 1mcg of T3 included until reaching the replacement of 50mcg of T4 for 12.5mcg of T3.

Marco D Angelo

PhD in biochemistry, specialized in enzymology and metabolic biochemistry with a background in pharmacology, he works in a molecular biology laboratory and in his spare time works as a high-performance trainer in addition to assisting other coaches.