Most men only know one number from their lab report: total testosterone.
It is the figure printed in bold, the one most clinics discuss, and the one that supplement brands obsess over.

But total testosterone alone does not tell you how your hormonal system is performing.

To understand whether testosterone supplements can help, and what kind, we need to start with the most important concept in male endocrine physiology:

Bioavailability.

How much of your testosterone is actually usable by your body.

This is why free testosterone is the real marker of androgen function, and why two men with identical total testosterone levels can feel completely different.

Total Testosterone: The Big Number That Misleads Most Men

Total testosterone is the sum of all testosterone circulating in your blood. But it exists in three states:

1. SHBG-bound testosterone (the majority)

• tightly bound
• biologically inactive
• cannot enter cells¹

2. Albumin-bound testosterone

• loosely bound
• can be released
• contributes to “bioavailable testosterone”

3. Free testosterone

• not bound to any protein
• represents only 1 to 3 percent of total testosterone
• the only form that can activate androgen receptors²

This means you can have a high total testosterone number while feeling like your system is running in low-power mode if SHBG is binding most of your testosterone and free testosterone is low.

Free Testosterone: The Hormone That Actually Matters

Free testosterone is the portion available for your tissues to use. It drives:

• libido
• morning erections
• muscle protein synthesis
• energy and motivation
• recovery
• erythropoiesis
• mood and cognition³

If free testosterone is low, your body is not receiving the androgen signal it needs, no matter how high your total testosterone appears on the lab sheet. This is why many men hear, “Your testosterone numbers look fine,” but still feel:

• flat
• tired
• unfocused
• low libido
• reduced performance

The labs do not match the lived experience because total testosterone does not reflect biological function.

What You Should Measure (The Real Hormone Panel)

To understand your hormonal profile, you need more than total testosterone.

A meaningful assessment includes:

• Total Testosterone
• Free Testosterone (calculated or via equilibrium dialysis)
• SHBG
• Albumin (for accurate calculations)

Optional but insightful:

• LH (to understand signaling)
• FSH
• Prolactin
• Estradiol
• Vitamin D
• Thyroid panel (TSH, FT4)
• Fasting insulin (for metabolic assessment)

This gives you a clear view of:

• production
• availability
• transport
• balance
• upstream signaling
• metabolic constraints
• inflammatory stressors

Why Understanding Metrics Comes Before Supplements

Before you buy a single supplement, you must know:

• Is the issue production? Raw materials?
• Is the issue signaling?
• Is the issue transport?
• Is the issue inflammation?
• Is the issue sleep?
• Is the issue metabolic?
  

Understanding total vs free testosterone is the foundation that allows every other part of the series to make sense.

Putting It All Together

Total testosterone is the big number everyone talks about. Free testosterone is the number that actually matters.

This distinction explains why men with normal labs can feel anything but normal, and why supplement strategies must be tailored to:

• your SHBG
• your free testosterone
• your signaling
• your metabolism
• your inflammation
• your sleep
• your physiology

This is the first real step toward building a targeted, effective testosterone optimization plan. Next, in Part 3: The Raw Materials, we cover the essential nutrients your body needs before it can produce testosterone efficiently.