My T3 on a carnivore diet is 1.5, TSH is normal, and T4 is 19. I can't quit keto as the carnivore diet keeps my autoimmunity (progressive multiple sclerosis) in full remission. Is T3 supplementation the only option?
Your current thyroid profile, with normal TSH, elevated Free T4, and low Free T3, reflects the well-documented metabolic adaptation to a zero-carbohydrate diet. I see this all the time, and it's one of the reasons why I do not recommend the carnivore diet long-term, even though it is part of the early scorch protocol. Everything you currently know about the benefits is what I want to see from someone in the first three months, but then I want you to transition to dry fasting and end it by reintroducing carbohydrates.
Your thyroid is producing T4 in sufficient quantities with minimal TSH stimulation, which confirms that your gland itself remains responsive and intact. Your issue lies in peripheral conversion.
When carbohydrate intake is absent, the body suppresses the diiodinase activity required to convert T4 into T3 within peripheral tissues. This suppression occurs because insulin, which rises in response to carbohydrate and amino acid availability, acts not only to regulate glucose uptake but also to signal energy abundance to the central nervous system. Consequently, when insulin remains chronically low, the body interprets this as a state of internal resource scarcity and shifts into a state of conservation, even if daily caloric intake is sufficient. One of the primary ways it does this is by limiting T3 production and action, thereby reducing metabolic rate and preserving energy for only the essential physiological functions required to keep you alive as an organism in the here and now.
Supplementing with exogenous T3 may increase your serum Free T3, but this is unlikely to produce meaningful symptomatic improvement. T3 is not primarily an endocrine hormone in the classical sense. It is produced and acts locally within tissues through autocrine and paracrine mechanisms. This means that raising its concentration in the blood does not guarantee increased intracellular action if the underlying suppressive environment remains unchanged, which it will if you continue to exclude carbohydrate from your diet.
The only way to reverse this state is to identify a form of carbohydrate that you can tolerate without exacerbating your autoimmune condition. That will involve targeted experimentation with specific starches, fruits, and juices, alongside working to address the immunological drivers of your food reactivity so that broader dietary flexibility becomes possible over time.
It is easier said than done, I know, but there is no other way around this, unfortunately. Attempting to pharmacologically bypass this adaptive state while maintaining the dietary condition that induces it is unlikely to result in a sustainable or physiologically coherent solution and may actually be harmful to your health in the long run.
Be sure to check out the Dry Fasting Club's members section, which features in-depth interviews and videos, as well as protocols and questionnaires that assess your dry fasting readiness levels.
