Understanding Testosterone: Total, Free, and SHBG Explained

You’ve just received your first bloodwork report. As you scan the page, you see not one, but multiple results related to testosterone. It can be confusing. This is the single most important concept to grasp in your entire TRT journey, and a foundational piece of hormone science.

This guide will demystify the key markers—Total Testosterone, Free Testosterone, and SHBG—using a simple analogy to make it crystal clear what they are, and more importantly, which one truly matters for how you feel.

Total Testosterone: The Entire Team Roster

Total Testosterone is exactly what it sounds like: the total amount of testosterone hormone circulating in your blood at that moment. It includes testosterone that is bound to proteins and testosterone that is "free."

Think of Total Testosterone as the entire roster of a football team. It tells you the total number of players signed to the team, but it doesn't tell you who is actually suited up and ready to play on game day.

While it's a useful starting number, it's a poor indicator of your true hormonal status on its own. Two men can have the exact same Total T level and feel completely different, all because of the next crucial protein.

SHBG: The Players on the Bench

SHBG (Sex Hormone-Binding Globulin) is a protein produced by your liver. Its job is to bind to sex hormones, including testosterone, and transport them through the bloodstream. When testosterone is bound to SHBG, it is inactive and cannot be used by your body's cells.

In our analogy, SHBG represents the players who are on the bench, injured, or otherwise unavailable to play in the game. The more players on the bench (high SHBG), the fewer players are available to be on the field.

• High SHBG can effectively "trap" a large portion of your Total Testosterone, leading to low active testosterone and symptoms, even with a "normal" Total T reading.
• Low SHBG means more of your Total Testosterone is unbound and active, which can be beneficial, but can also sometimes lead to more side effects if not managed well.

Free Testosterone: The Players on the Field

This is the hero of the story. Free Testosterone is the small fraction (typically 1-3%) of testosterone that is not bound to SHBG or any other protein. This is the biologically active, usable hormone that can enter your cells and exert its powerful effects on muscle, bone, brain, and libido.

Free Testosterone is the number of players actually on the field, running plays, and winning the game. This is the number that is most directly correlated with your symptoms and your sense of well-being.

Optimizing your Free Testosterone level is the primary goal of a modern, effective TRT protocol. This is why simply getting a prescription to raise your Total T isn't enough; a good doctor focuses on how that protocol impacts your all-important Free T.

Putting It All Together: Why the Ratio is Everything

As you can see, no single number tells the whole story. Your hormonal health is about the relationship—the ratio—between these three markers. A man with a Total T of 800 ng/dL but very high SHBG might have lower Free T (and feel worse) than a man with a Total T of 600 ng/dL and very low SHBG.

Now that you understand the key players in the testosterone family, the next step is to understand testosterone's most important counterpart in the male body: Estrogen.