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What is testosterone?

Testosterone is the primary male hormone responsible for sexual health and development, in addition to other physiological functions. Having proper levels of testosterone is essential not only for males but for females, too. An imbalance of testosterone can have negative effects on both reproductive and overall health.

Why is it included in the Balance Axis?

In men, testosterone regulates sex drive (libido), bone mass, fat distribution, muscle mass and strength, and the production of red blood cells and sperm. Given its many functions, testosterone forms the core metric of our Balance score for the male profile and is also included in the male Hormone+ panel. Symptoms of low testosterone may include reduced sex drive, erectile dysfunction, low sperm count, and other emotional and physiological changes. 

How can I better understand my results?

Free and total testosterone are two different measurements. Total testosterone quantifies, as the name suggests, the overall quantity of testosterone including molecules that are both free (unbound) and bound to proteins (mainly SHBG and albumin). On the other hand, a measure of free testosterone does not measure molecules that are bound to proteins. This is an important measurement as free testosterone is generally more bioactive than bound testosterone. People who may be experiencing symptoms of low testosterone but have normal levels of total testosterone may be advised to take a free testosterone test.

Free and total testosterone ranges vary based on many factors, including age. The Cincinnati Children's Hospital released a list of normal free and total testosterone ranges in males by age.

Normal total testosterone in males:

  • Age 18 - 40: 3.0 - 10.8 ng/mL
  • Age 40 - 60: 3.0 - 8.9 ng/mL
  • Age 60+: 3.0 - 7.2 ng/mL

Normal free testosterone in males:

  • Age 18+: 0.047 - 0.244 ng/mL

According to the Cleveland Clinic, the American Urology Association (AUA) considers low total testosterone to be < 3.0 ng/mL for adults. However, some researchers and healthcare providers believe that no more than 2.50 ng/mL should be indicative of low testosterone.

Testosterone, like many hormones, follows a diurnal rhythm, peaking in the morning and dipping in the early evening. Peak secretion occurs between 7 and 10 a.m., which is why testing testosterone levels in the morning helps to limit variations, particularly in younger men.

Prinz, Patricia & Bremner, William & Vitiello, Michael. (1983). Loss of Circadian Rhythmicity in Blood Testosterone Levels with Aging in Normal Men*. J Clin Endocrinol Metab. 56. 10.1210/jcem-56-6-1278.

Low testosterone is more likely to affect those who are older, obese, have type 2 diabetes or HIV/AIDS, have sleep apnea, or have chronic conditions such as kidney or liver dysfunction. Since abnormally high or low testosterone levels may indicate problems with the testicles, pituitary gland, or hypothalamus, it is important to consult with your physician if you are concerned about your levels.

A few lifestyle changes you can make to help improve low testosterone levels include:


Where can I learn more?

Andrew Huberman has a masterclass on testosterone for males.

Harvard Medical School - Testosterone: What It Is and How It Affects Your Health

Cleveland Clinic - Testosterone