What is Free Testosterone?
Testosterone exists in two forms: bound and unbound. Most testosterone is attached to proteins like sex hormone-binding globulin (SHBG) and albumin, which limit how much can enter your cells.
Only a small fraction of testosterone is free — about 2-3% in men1 and 1.5% in women2 — meaning it’s unbound and available to move into tissues to support muscle growth, bone density, red blood cell production, libido, mood, and cognitive function.
In men, testosterone is produced in the Leydig cells in the testes. In women it’s produced in the ovaries and adrenal glands.
Why Does Free Testosterone Matter?
- Supports libido and sexual function by activating testosterone receptors in the brain and reproductive tissues, increasing nitric oxide, and improving blood flow
- Promotes muscle growth and maintenance by signaling muscle cells to build new protein and slow down muscle breakdown
- Boosts cellular energy production by helping cells turn nutrients into usable energy
- Supports mood, motivation, and mental clarity by influencing dopamine and serotonin, the brain chemicals that regulate drive and emotional balance
- Maintains bone strength by stimulating bone-building cells and supporting healthy hormone balance that keeps bones dense and resilient
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How to Interpret Free Testosterone?
(Ranges may vary slightly by lab)
Standard reference ranges represent the middle 95% of healthy individuals but don’t necessarily reflect levels associated with longevity. Optimal ranges are derived from clinical guidelines, peer-reviewed research, and real-world outcomes data, with an emphasis on levels associated with peak functioning and reduced disease risk.
Benefits of Optimizing Free Testosterone
- Improved muscle mass and strength
- Decreased visceral (belly) fat
- Reduced risk of osteoporosis and fractures
- Improved sexual health
- Better mood1
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Low Free Testosterone Levels
Symptoms:
Causes:
- Aging
- Obesity or metabolic issues
- Chronic illness or infections
- High alcohol consumption
- Smoking
- Chronic stress
- Certain medications (opiates; antidepressants)
- Elevated sex hormone binding globulin (SHBG)
- Thyroid dysfunction
Healthspan Impacts:
- Increased body fat and decreased muscle mass
- Increased risk of depression
- Risk of osteoporosis and fractures2
- Higher rates of metabolic syndrome3
- Increased risk of cardiovascular disease and mortality4
High Free Testosterone Levels
Symptoms:
- Unexplained fatigue
- Acne
- Increased body hair
- Hair loss
- Irregular periods (women)
- High libido
- Mood swings
- Aggression
- Low sperm count (men)
Causes:
- Anabolic steroid use
- Overly high doses of testosterone replacement therapy (TRT)
- Polycystic ovarian syndrome (PCOS – women)
- Congenital adrenal hyperplasia
- Low sex hormone binding globulin (SHBG)
- Certain medications (e.g., antiseizure medications)
- Tumors (rare)
- High alcohol consumption
Healthspan Impacts:
- Increased risk of high blood pressure and cardiovascular disease
- Increased risk of insulin resistance5
- Potential cholesterol abnormalities (lower HDL)
How Hone Treats Out of Range Free Testosterone
Your Hone physician will evaluate free testosterone alongside a full sex hormone profile that may include testosterone biomarkers like total testosterone, SHBG, albumin, LH (in men), and estradiol, as well as your symptoms, and overall health. From there, they can map out a treatment plan that may include medications, supplements, and lifestyle changes.
- Testosterone replacement therapy (TRT) (men and women)— to directly raise circulating testosterone levels when the body is not producing enough. TRT can be delivered through injections, cream, or oral lozenges called troches
- Enclomiphene or clomiphene citrate (men) — to stimulate the brain’s release of luteinizing hormone (LH) and follicle stimulating hormone (FSH), encouraging the testes to produce more of their own testosterone
- Anastrozole (men) — to reduce conversion of testosterone into estradiol when estrogen levels are suppressing testosterone production
* If you are on treatment to increase testosterone, regular monitoring is essential. Your doctor will check your total testosterone levels every 3-6 months to ensure you stay within a healthy range.
- Reduce chronic stress
- Get regular aerobic and resistance training, but avoid overtraining or excessive exercise
- Get 7-8 hours of sleep per night
- Maintain an ideal body weight
- Avoid tobacco
- Limit alcohol
- Eat a healthy, balanced diet and limit sugar and processed foods
Rojas-Zambrano, J.G., et al. (2025). Benefits of Testosterone Hormone in the Human Body: A Systematic Review. Cureus.
↑Golds, G., Houdek, D., & Arnason, T. (2017). Male Hypogonadism and Osteoporosis: The Effects, Clinical Consequences, and Treatment of Testosterone Deficiency in Bone Health. International Journal of Endocrinology.
↑Mheid, I.A., et al. (2015). Low testosterone in men predicts impaired arterial elasticity and microvascular function. International Journal of Cardiology.
↑Hyde Z, et al. (2012). Low free testosterone predicts mortality from cardiovascular disease but not other causes: the Health in Men Study. J Clin Endocrinol Metab.
↑Mohammadi-Shemirani, P., et al. (2020). Effects of lifelong testosterone exposure on health and disease using Mendelian randomization. ELife.
↑Pilz, S., et al. (2011). Effect of vitamin D supplementation on testosterone levels in men. Horm Metab Res.
↑Cinar, V., et al. (2011). Effects of magnesium supplementation on testosterone levels of athletes and sedentary subjects at rest and after exhaustion. Biological trace element research.
↑Te, L., et al. (2023). Correlation between serum zinc and testosterone: A systematic review. J Trace Elem Med Biol.
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Reviewed for Accuracy by Our Medical Review Board
This biomarker information has been reviewed by a member of Hone’s medical review board. As part of the medical review team, physicians fact-check this content against the latest research and their own experience treating their patients.
Ashley Winter, M.D., is a board-certified urogynecologist trained at Weill Cornell and Cleveland Clinic. She specializes in female and male sexual dysfunction, urinary issues, genital pain, and hormone therapy.
James Staheli, D.O., is the Medical Director for Broad Health, Hone Health’s affiliated medical practice and a family medicine doctor in Atlanta, Georgia.
