calculate FT3 to RT3 here

[007999]

tpauk.com/main/how-to-calcu...

[jimh111]

If I understand correctly the rT3 figure is the Total rT3 whereas fT3 is of course the Free T3. Thus, I'm not sure there is any point in calculating a ratio - what proportion of rT3 is free? Also, I never seen any study into the relative binding affinity (to thyroid hormone receptors) of T3 and rT3. How do they compete for receptors.

This is not to say rT3 is not relevant, I'm sure it is. It's more a question of whether it is normal or unusually high. Beyond a simple high or low I don't think there is any science behind calculated ratios, so I'd beware trying to read too much into the numbers or even spending money on tests.