How to correctly interpret your testosterone test

A testosterone result on a lab report is not a diagnosis. Drs. Jordan Fagen and Austin Baraki of the Barbell Medicine podcast explain why the number in your report is only the starting point, and what additional information a real clinical evaluation actually requires.

How testosterone works: the HPG axis

Testosterone production depends on a feedback loop with at least three points where it can fail. The hypothalamus broadcasts GnRH pulses, the pituitary receives them and releases LH and FSH into the bloodstream, and the testes respond by producing testosterone. As testosterone accumulates, it sends a signal back to the hypothalamus to reduce the broadcast.

A single low testosterone value tells you nothing about where in this chain the failure is. High LH and FSH alongside low testosterone indicates the problem is at the testes themselves, called primary hypogonadism. Low or inappropriately normal LH and FSH with low testosterone means the failure is upstream in the brain, at the hypothalamus or pituitary, called secondary or central hypogonadism. Each scenario requires a different investigation.

What total testosterone actually measures

Most circulating testosterone is bound to carrier proteins and unavailable to the tissues:

• About 40-45% is tightly bound to SHBG (sex hormone-binding globulin) and effectively locked up.
• Approximately 50% is more loosely bound to albumin.
• Only about 2% circulates free and available to act on tissues.

The standard lab test measures all three fractions together. If SHBG is abnormally high (from hypothyroidism, advancing age, or chronic liver disease) or low (from obesity, type 2 diabetes, or exogenous androgen use), the total value can be misleading in either direction.

The saturation model: higher is not better

For decades, testosterone was feared to accelerate prostate cancer. Studies revealed something nobody predicted: above a threshold of roughly 250 ng/dL, raising serum testosterone further produces no additional effect on the prostate. The receptor is already occupied.

This ceiling effect, the saturation model, applies to libido and erectile function as well. Framingham and HIM dataset findings show libido plateaus within the lower end of the reference range. A man with 600 ng/dL is not more libidinous than a man at 400 ng/dL. Within the normal physiological range, chasing a higher number doesn't deliver the effect being marketed.

Only three symptoms actually correlate with low testosterone

The European Male Aging Study assessed 32 symptoms commonly attributed to low testosterone in over 3,000 men aged 40 to 79. Only three correlated at a statistically significant and reproducible level with low values, and all three are sexual:

1. Decreased frequency of morning erections.
2. Decreased frequency of sexual thoughts.
3. Erectile dysfunction.

The other 29 symptoms, including fatigue, brain fog, low mood, and poor concentration, did not survive the analysis after adjusting for age and comorbidities. They are real symptoms, but they have dozens of more likely causes before testosterone enters the picture. The wellness clinic business model is built on precisely that mismatch.

How the lab draw must be done

Testosterone testing has strict validity requirements:

• Drawn between 7:00 and 10:00 a.m. (reference ranges are built on morning data).
• Fasting, since eating a meal can transiently lower total testosterone.
• Not during an acute illness.
• Without severe recent sleep deprivation if avoidable.

Roughly half of initially low total testosterone values will normalize on repeat testing without any treatment. That's why guidelines require a confirmatory second draw under correct conditions, plus LH, FSH, and SHBG on the same panel.

Exercise as the first intervention

A 12-week Australian clinical trial in 80 men in their 50s and 60s with low-normal testosterone compared testosterone alone, exercise alone, both combined, and neither. Exercise improved aerobic capacity by 10-13%. Testosterone alone produced no improvement in aerobic fitness. Exercise was the only driver of strength gains across all groups. The authors' direct conclusion: exercise should be evaluated as an anti-aging intervention in preference to testosterone in middle-aged men with low-normal testosterone levels.

Conclusion

A low number on a testosterone lab report is not a diagnosis or a prescription. A real evaluation requires symptoms weighted toward the sexual complaints, a correctly drawn morning testosterone confirmed on repeat, LH, FSH, and SHBG to localize the problem, and an active search for modifiable causes like obesity, sleep apnea, or chronic sleep deprivation. The number in the report is only the beginning of the investigation, not the end.