Testosterone: What's the Optimal Range for Men Over 35?
Lab reference ranges for testosterone are designed to flag disease, not optimize performance. Here's what the research says about the levels associated with peak vitality, muscle mass, and cognitive function.
The Problem with Standard Reference Ranges
Most labs report total testosterone as "normal" anywhere between 264–916 ng/dL. That's a 3.5-fold range. A man at 270 ng/dL and a man at 900 ng/dL are both "normal" — but they will feel and perform very differently.
Standard reference ranges are designed to identify hypogonadism (a medical condition), not to define the levels associated with optimal health, energy, libido, and body composition.
What Does the Research Say About Optimal Testosterone?
A landmark study published in the *Journal of Clinical Endocrinology & Metabolism* (2013) found that symptoms of testosterone deficiency — fatigue, reduced libido, loss of muscle mass, increased body fat — begin appearing below 400 ng/dL in most men, even though this is technically "normal."
For men over 35 who want to optimize performance and longevity, most functional medicine practitioners and longevity researchers target:
| Marker | Optimal Range |
| Total Testosterone | 600–900 ng/dL |
| Free Testosterone | 15–25 pg/mL |
| SHBG | 20–40 nmol/L |
| Estradiol (E2) | 20–30 pg/mL |
| LH | 3–8 mIU/mL |
Why Free Testosterone Matters More Than Total
Total testosterone measures everything in your blood — but most of it is bound to proteins (SHBG and albumin) and unavailable to your cells. Free testosterone is the biologically active fraction that actually enters cells and produces effects.
Two men with identical total testosterone of 600 ng/dL can have very different free testosterone levels depending on their SHBG. High SHBG (common with aging, high-fiber diets, and thyroid issues) binds more testosterone and leaves less free.
Natural Ways to Optimize Testosterone
Before considering any medical intervention, these lifestyle factors have strong evidence:
- Sleep 7–9 hours — testosterone is primarily produced during deep sleep; one week of 5-hour nights reduces testosterone by 10–15%
- Reduce body fat below 20% — adipose tissue converts testosterone to estrogen via aromatase
- Resistance training — compound lifts (squat, deadlift, bench) acutely raise testosterone by 15–25%
- Zinc and magnesium — deficiencies in both are strongly correlated with low testosterone
- Reduce alcohol — even moderate drinking (2–3 drinks/day) suppresses testosterone by 6–23%
- Manage cortisol — chronic stress directly suppresses the HPG axis
Body150 tracks your testosterone alongside SHBG, estradiol, and LH to give you the full hormonal picture — not just a single number.
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