The above is based on the Harvard Protocol developed by Dr. Abraham Morgentaler.
There is no universal range or set of numbers all physicians hold to. And there's not one all labs hold to in terms of normal ranges.
Please keep in mind that normal ranges are simply an average of a large segment of the population. They consider no other factors. More importantly, Normal does not mean Optimal. Dr. Morgenataler said it best and I'm paraphrasing, as you age your eyesight typically gets worse. Do you say this is normal for your age and just live with it or do you go out and get glasses or contacts? Why is testosterone any different?
The word "Normal" should be banned and outlawed in the TRT world. It's a useless word.