It's Not How Much You Have; It's How Much You Can Use
When it comes to testosterone, it's not enough to look at how much you have in total—what really matters is how much is biologically available for your body to use. Most of the testosterone in your bloodstream is bound to protein and cannot enter cells to perform its critical functions:
| State | Percentage | Usability |
|---|
| Bound to Sex Hormone-Binding Globulin (SHBG) | 60-70% | Unavailable for cellular use |
| Bound to Albumin | 30-40% | Readily accessible to be converted into active state |
| Free Testosterone | 1-2% | Immediately available to enter cells |
Of these states, free testosterone is the most important for driving the hormone's effects, including muscle growth, energy levels, and overall metabolic health. Even if your total testosterone levels are normal, a low level of free testosterone still means your body does not have enough testosterone available to function properly. It's the difference between owning a car and having gas in the tank.
How Free Testosterone Changes With Age
Testosterone levels rise rapidly during puberty, fueling key developmental changes in both males and females. However, these levels don't stay high forever. In men, free testosterone begins a steady decline from its peak starting in their 30s, dropping by an average of 1.2% per year. By comparison, free testosterone levels in women decline rapidly during menopause and then stabilize after.
Men
Women
Low Testosterone Hits Harder With Age in Men
By the time men reach their 60s and 70s, about 30% have low free testosterone levels. By their 70s and 80s, that figure climbs to a staggering 70%. The chart above, showing average free testosterone levels for men across age groups, underscores the scale of this issue. For men in their 70s and older, the majority fall into non-optimal ranges—even when accounting for natural variability within two standard deviations.
This widespread decline in testosterone isn't just a statistical trend—it represents a significant health consideration for aging men, influencing everything from energy and mood to muscle mass and overall vitality.
Are You at Risk for Low Testosterone in the Future?
At Instalab, we've developed a
simple, user-friendly tool to help you assess your testosterone trajectory over time. By comparing your current testosterone levels against the average age-related decline, the tool generates a clear visual projection of your future levels.
To illustrate, take a look at my personal free testosterone data below. At 32 years old, my levels were objectively within the normal range—not low by any standard. While that's great news now, the projection also revealed that by my late 70s, I was on track to experience low testosterone levels. Since I have no interest in losing muscle mass or increasing my risk of cardiovascular issues, that was a wake-up call.
Rather than immediately turning to medication, I decided to focus on two areas where I had significant room for improvement: exercise and sleep quality. These lifestyle changes had a dramatic impact, boosting my free testosterone levels and bringing them into a much safer range. Now, I'm far less likely to face low testosterone as I age.
I'm sharing this data not because of what it means for my own health, but because it highlights an important message: small, intentional lifestyle adjustments can have a profound impact on your future well-being. If you're curious about your own trajectory, this
tool is a great place to start.
What Can You Do?
Weight management is one of the most effective ways to influence testosterone levels. Research shows a strong link between excess body fat and reduced testosterone production. Maintaining a healthy weight not only improves testosterone levels but also gives you immediate, tangible feedback on your progress.
That said, crash diets or extreme eating plans aren't the solution. These approaches are often unsustainable and can lead to yo-yo effects that are ultimately counterproductive. Instead, the key lies in finding a balanced diet and exercise routine that fits your lifestyle—something enjoyable and sustainable in the long term.
It's also important to acknowledge that tools like BMI, while commonly used, have their limitations. For instance, someone with a high muscle mass might be labeled "overweight" on the BMI scale despite being in excellent health. That's why it's crucial to look beyond numbers on a chart. Ultimately, you're the best judge of your body—whether it's carrying excess fat that could be affecting your testosterone levels or finding a balanced approach to shed it sustainably.
Skimping on Sleep Tanks Your Testosterone
Sleep plays a crucial role in maintaining healthy testosterone levels too. Research indicates that for every hour of sleep lost, total testosterone levels drop by an average of 5.85 ng/dL in men. For many patients at Instalab—particularly high achievers balancing demanding careers and lifestyles—this becomes a significant issue. Beyond its impact on testosterone, sleep deprivation carries a host of other health risks, but its direct effect on hormonal balance is particularly concerning.
Measuring Testosterone Levels
At Instalab, we've simplified testosterone monitoring with our
at-home test kit. It measures both total and free testosterone, along with key related proteins like SHBG and albumin. These biomarkers provide a detailed picture of your body's free testosterone levels and whether you will be in an optimal range as you age.
Sources
- Gray, A., Feldman, H., Mckinlay, J., & Longcope, C. (1991). Age, disease, and changing sex hormone levels in middle-aged men: results of the Massachusetts Male Aging Study. The Journal of clinical endocrinology and metabolism, 73(5), 1016-25. https://doi.org/10.1210/JCEM-73-5-1016
- Handelsman, D., Yeap, B., Flicker, L., Martin, S., Wittert, G., & Ly, L. (2015). Age-specific population centiles for androgen status in men. European journal of endocrinology, 173(6), 809-17. https://doi.org/10.1530/EJE-15-0380
- Haring, R., Hannemann, A., John, U., Radke, D., Nauck, M., Wallaschofski, H., Owen, L., Adaway, J., Keevil, B., & Brabant, G. (2012). Age-specific reference ranges for serum testosterone and androstenedione concentrations in women measured by liquid chromatography-tandem mass spectrometry. The Journal of clinical endocrinology and metabolism, 97(2), 408-15. https://doi.org/10.1210/jc.2011-2134
- Hijazi, R., & Cunningham, G. (2005). Andropause: is androgen replacement therapy indicated for the aging male?. Annual review of medicine, 56, 117-37. https://doi.org/10.1146/ANNUREV.MED.56.082103.104518
- Nanba, A., Rege, J., Ren, J., Auchus, R., Rainey, W., & Turcu, A. (2019). 11-Oxygenated C19 Steroids Do Not Decline With Age in Women. The Journal of clinical endocrinology and metabolism, 104(7), 2615-2622. https://doi.org/10.1210/jc.2018-02527
- Patel, P., Shiff, B., Kohn, T., & Ramasamy, R. (2018). Impaired sleep is associated with low testosterone in US adult males: results from the National Health and Nutrition Examination Survey. World Journal of Urology, 37, 1449-1453. https://doi.org/10.1007/s00345-018-2485-2
- Schatzl, G., Madersbacher, S., Temml, C., Krenn-Schinkel, K., Nader, A., Sregi, G., Lapin, A., Hermann, M., Berger, P., & Marberger, M. (2003). Serum androgen levels in men: impact of health status and age. Urology, 61(3), 629-33. https://doi.org/10.1016/S0090-4295(02)02252-5
- Travison, T., Araujo, A., Kupelian, V., O'Donnell, A., & Mckinlay, J. (2007). The relative contributions of aging, health, and lifestyle factors to serum testosterone decline in men. The Journal of clinical endocrinology and metabolism, 92(2), 549-55. https://doi.org/10.1210/JC.2006-1859
Alex Cheung
