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Free Testosterone: What Is It?

Testosterone is essential for men’s and women’s well-being

Free Testosterone: What Is It?

Published: July 2023

By: Jessica Monge, Health & Wellness Writer

Scientifically Reviewed By: Michael A. Smith, MD

Testosterone is essential for our well-being. It's produced in the testes in men and ovaries in women (yes, women have this sex hormone, too, but in smaller amounts), and the adrenal glands (located on top of each kidney) in both men and women. This androgen hormone is involved in several aspects of our health, including metabolism, energy, sex drive, muscle mass and strength, inflammatory response, cognition, mood and the list goes on.

So how do you know if you have enough testosterone to be at your healthiest? The answer is not as simple as you may think. There's free testosterone (free T), bound testosterone, and total testosterone levels (total T). So, what's the difference? How do you measure your testosterone levels and what can you do if they're less than ideal? Here's the lowdown on what you need to know.

Testosterone (Free with Total) Blood Test

What is free testosterone?

Free testosterone is not attached to SHBG and is available for cells to use

Free testosterone refers to the testosterone that is unattached or not bound to a sex hormone binding globulin (SHBG) or albumin, the main protein present in the blood. Most testosterone in the blood, about 98 percent, is bound to a protein, in particular the sex hormone binding globulin (SHGB).

So what happens to testosterone when it's bound to a protein? Well, just like being chained up would hinder your ability to be at your most vital, this sex hormone is believed to be able to have the most impact on the body when it's "liberated" as well. Theoretically speaking, at least. The mechanism of how your cells interact with testosterone is not fully understood; however, the prevailing theory is that free or unbound testosterone is biologically active or available for your cells to absorb and use, while protein-bound testosterone is believed to have a minimal effect on cells, if any. And since only two percent of testosterone is "free T," having not only enough total testosterone but enough free testosterone may really matter.

What's the difference between free testosterone and total testosterone?

This is a tricky question—whether you're talking about free T or total T, you are referring to the same hormone; there's no chemical difference. However, when testosterone is bound to a protein (whether that's SHBG, albumin, or other binding proteins) it may be less usable by your body than free testosterone.

How is free testosterone measured?

Luckily, it's easy to know your testosterone levels—if you're thinking lab test, you're correct! A blood test will help you discover whether you have low testosterone or normal testosterone levels.

Since there are several forms of testosterone circulating through your body, there are three types of tests that can help you measure the different forms of testosterone.

Total testosterone test:
This is the most common type of blood test, and it measures both free and protein-bound T levels, which means the results show total testosterone levels.
Free testosterone test:
This lab test measures the free testosterone concentration in your blood, which analyzes the active or free T form of this sex hormone. It's not as common a measurement, but if you want to know if you have low free testosterone, this is an excellent starting point.
Active testosterone test:
This test (which also isn't very commonly ordered, but offers tremendously valuable information) measures free T levels and testosterone that's loosely bound to proteins like albumin and SHBG (albumin-bound or SHBG-bound).

If you haven't been feeling like your usual self, you may want to consider checking your hormone balance. Ensuring you have normal testosterone levels (along with other sex hormones) can help you identify and address any possible causes that could impact your well-being, including:

Sleep
Mood
Sex drive
Metabolism
Immune challenges
Muscle and bone mass

Blood testing that goes beyond just T levels and assesses whether your hormones are in balance can be found in gender-specific blood panels, such as a comprehensive male panel blood test (also available for females).

Learn more about Male Hormone Restoration

What free testosterone level is good?

Aging men and women experience a decline in free testosterone levels

Measuring your testosterone concentration (both free and total testosterone levels) can help you better understand what's going on behind the scenes of your biology. Your results for testosterone levels will vary depending on your age, gender, lifestyle and what lab test you do. Typically, results are considered "normal" when testosterone levels are as follows:

Total testosterone for men: 250-1100 ng/dL
Total testosterone for women: 15-75 ng/dL

However, "normal" isn't the same as "optimal." The lower end of the spectrum may be teetering on "too low" for some people. To maintain youthful vigor and well-being, some experts recommend these ranges:

Men should have total testosterone of 600-900 ng/dL
Women should have total T levels of 35-60 ng/dL

How does low testosterone impact my health?

People with low testosterone may experience changes in sex drive, energy levels, heart health, sleep, cognitive performance, and even muscle mass and strength. Keep in mind that age-related decline of total testosterone levels occurs naturally over time.

What to do if your free testosterone is low?

Once you get your results, the important thing is not to panic if your levels are low. Lower levels are normal in middle-aged and older men (and women), but you don't have to take that decline laying down. Partner with your healthcare provider to keep tabs on your T levels.

Additionally, there are nutritional changes you can make that may improve your levels. An excellent starting point is ensuring you get balanced meals—think Mediterranean diet—to help keep sex hormones (and all of you) in homeostasis, or a state of equilibrium and harmony. Pomegranate and cacao were shown to benefit testosterone levels in studies. Research also suggests the trace mineral zinc can help support hormone balance and overall testosterone levels, especially in men. And chrysin, a flavonoid found in plants, honey and propolis has been shown to support healthy levels of this sex hormone by inhibiting the activity of aromatase, and enzyme that converts testosterone to estrogen.

How do you increase free testosterone?

Lifestyle changes and nutrients can help support healthy free testosterone

Now that you better understand what free testosterone is and how total testosterone is measured, let's go over lifestyle changes you can make that can increase free and total testosterone. In addition to eating nutrient-rich meals, you can increase your T levels with specific healthy behaviors:

Work up a sweat:
Regular exercise, both aerobic (the kind that gets you sweating and breathing heavily) and resistance training like weightlifting can help increase testosterone production. And, of course, exercise is unequivocally a cornerstone of head-to-toe wellness; research shows that it helps improve cognition, heart health, mood, sleep and more!
Manage a healthy weight:
Maintaining a healthy weight is about being healthy (feeling confident and looking good in your favorite pair of jeans is a plus, of course). Research shows that excess fat can trigger the activity of aromatase, an enzyme that converts testosterone to estrogen, resulting in low testosterone levels.
Prioritize uninterrupted sleep:
Restful shuteye, at least seven to nine hours of deep sleep (the kind that helps you feel refreshed when you wake up), is essential for your overall health, including total testosterone. Studies show that most of your body's testosterone production occurs while you're sleeping, especially during REM sleep (rapid eye movement). Not getting enough REM sleep is associated with low testosterone levels.
Watch your blood sugar levels:
Maintaining healthy blood sugar levels also helps maintain healthy total testosterone, especially as you age.
Goodbye, tobacco and excess alcohol:
Studies show that tobacco products have a direct impact on total testosterone, and alcohol consumption, in particular more than two drinks a day, has also been shown to increase the conversion of testosterone to estrogen.

About the Author: Jessica Monge has a bachelor's degree in biological sciences & neuroscience and a master's degree in comparative studies and related languages from Florida Atlantic University. She worked as a tutor, freelance writer and editor before joining Life Extension, where she is currently a Digital Content Writer.