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.