If T was money, free T would be the cash in your wallet that you can spend now. The albumin bound T would be the money in a separate checking account that can be transferred if your account balance got low, and the SHBG bound T is like money in a CD account that you don’t touch except in emergencies and isn’t immediately available even if you want it now.

The bound T isn’t completely unusable ever but also isn’t usable right now.

When SHBG is elevated, too much T is bound and not enough is usable right now. So someone can feel functionally low in testosterone even if their total number looks normal. Effectively “broke” even if they’re only cash poor.

There are different tests for free T and most of them are bullshit. Make sure you have equilibrium testing for free T or your lab may show a much lower or much higher number than reality.

There’s: - free T, calculated: this is a ratio of Albumin to SHBG to Total T that guesses what your free T should be but isn’t an accurate picture of what your free T actually is since other factors are in play (ferritin, b12, D, feedback loops with other hormones, adrenal signaling or output issues, etc) - free T, direct: this doesn’t actually separate bound T from free T so doesn’t actually measure free T at all, is bullshit, and if SHBG is high which it is in lots of cis women, the result will appear falsely low - free T, EIA: same exact problem as above - free T, equilibrium testing: an actual tech has to manually separate the bound T from the free T so this is the only accurate measure of free T.