Free Testosterone vs Total Testosterone: The Number That Actually Matters
Your total T can look normal while your free T is in the basement. Here's how to read the panel your doctor probably won't explain.
The two numbers on your lab report
Total testosterone measures every molecule of T in your bloodstream — bound, unbound, or protein-attached. Most reference ranges span 264–916 ng/dL for adult men.
Free testosterone measures only the fraction that isn't bound to SHBG or albumin — roughly 1–4% of the total. Free T is the portion your cells can actually use. It's the number that correlates most tightly with how you feel.
Why total T can look normal while free T is low
SHBG rises with age, chronic caloric restriction, hyperthyroidism, and certain medications. As SHBG rises, more of your testosterone becomes protein-bound and unavailable. A man with total T of 550 ng/dL and SHBG of 65 nmol/L can have less bioavailable T than a man with total T of 400 and SHBG of 25.
This is why so many men in their 40s feel low-T symptoms despite 'normal' total testosterone. The physician looks at one number; the physiology tells a different story.
How to order and interpret the right panel
Request a morning (7–9 AM), fasted panel that includes: total testosterone, free testosterone (equilibrium dialysis or calculated), SHBG, albumin, estradiol (sensitive assay), LH, FSH, and prolactin. If your clinic only offers a basic panel, at minimum insist on total T, free T, and SHBG.
What actually moves free T
Lowering SHBG raises free T with no change in total. Interventions with clinical evidence include: reducing chronic caloric restriction, correcting protein intake (>1.6 g/kg), zinc and boron sufficiency, tongkat ali, and reducing endurance-training volume if excessive.
Raising total T (weight training, sleep, body-composition improvement) also raises free T proportionally as long as SHBG doesn't rise in parallel.
| Marker | Typical adult male range | What it tells you |
|---|---|---|
| Total testosterone | 264–916 ng/dL | Total production |
| Free testosterone | 6.8–21.5 pg/mL | Biologically active fraction |
| SHBG | 10–57 nmol/L | How much T is bound and unavailable |
| Albumin | 3.4–5.4 g/dL | Second binding protein (weakly bound) |
| Estradiol (sensitive) | <40 pg/mL | Aromatization / estrogen balance |
| LH | 1.7–8.6 IU/L | Pituitary signal to make testosterone |
Frequently asked questions
- Which number should I care about most?
- Free testosterone — it's what your tissues actually use. But interpret it alongside SHBG and how you feel.
- Why is my total T normal but I feel awful?
- Most often: high SHBG, elevated estradiol, poor sleep, or thyroid dysfunction. Order a full panel, not just total T.
- Can I raise free T without raising total T?
- Yes — by lowering SHBG. Boron, tongkat ali, adequate protein, and reducing chronic caloric restriction all help.
Compare our editor-rated testosterone-support formulas or take the 2-minute quiz to find what fits your goals.