Quick answer: Free testosterone is the small fraction of testosterone that is not bound to proteins and can act on tissues. It is especially useful when SHBG is high or low, because total testosterone can look normal while free testosterone is low, or vice versa. It helps evaluate low-T symptoms in men and androgen excess in women.
What is Free Testosterone?
Most testosterone is bound to SHBG or albumin. Free testosterone is the unbound portion available to cells. This marker is part of the Healthspan Assessment panel available to my 1-on-1 patients.
Why Free Testosterone matters
- Reflects active testosterone
- Clarifies results when SHBG is abnormal
- Evaluates PCOS and androgen excess in women
Understanding your result
Reference ranges vary by lab, age and sex. Your provider interprets your result against the lab’s range and your overall picture, rather than chasing a single number. Functional labs are optional. They can be helpful in more complex cases, and in my practice they are available only to patients working 1-on-1 with me.
What low Free Testosterone can mean
- High SHBG (aging, hyperthyroidism, low-calorie diets)
- Low total testosterone
- Poor sleep and chronic stress
What high Free Testosterone can mean
- Low SHBG from insulin resistance
- PCOS
- Testosterone or steroid use
What affects Free Testosterone
- SHBG levels
- Insulin
- Thyroid
- Test method (calculated or measured)
Ways to support healthy levels
- Improve insulin sensitivity (see SHBG)
- Strength train and sleep well
- Eat enough protein and calories
- Read alongside total testosterone
Free Testosterone and healthy aging
Active testosterone supports muscle, bone and metabolic health, and its decline contributes to muscle loss with age.
When to see a naturopathic doctor
- Low-T symptoms with normal total testosterone
- Signs of PCOS
- Abnormal SHBG
- You want hormone results explained
Want help making sense of your labs?
A free 15-minute consultation with Dr. Kneessi. No cost, no obligation. In-office in Odenton, MD or by telehealth.
Frequently asked questions
What is free testosterone?
The unbound portion of testosterone that can act on tissues.
Why is free testosterone low when total is normal?
High SHBG can bind more testosterone, lowering the free portion.
Is calculated free testosterone accurate?
Calculated values using total testosterone, SHBG and albumin are widely used.
Does free testosterone matter for women?
Yes. High free testosterone is common in PCOS.
Sources
This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before starting supplements or changing medications, especially if you are pregnant, nursing, or managing a health condition.
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