Free Testosterone Levels vs. Total T: What’s the Difference?
Not all testosterone is created equal.
- Total testosterone is the total amount of testosterone in your body.
- Free T is the type of T your body uses, and knowing your free testosterone levels is an important marker of good health.
- If your free testosterone levels are too low, testosterone replacement therapy may be needed.
Testosterone matters. This vital male sex hormone plays a key role in regulating important bodily functions from how much weight you can lift to energy levels, sex drive, and more. But not all testosterone is equal. Testosterone is found throughout your bloodstream in two main forms: total testosterone (total T) and free testosterone (free T).
Differentiating between your Total T and free testosterone levels is a key part of understanding how T works in your body as well as how to optimize your health.
Testosterone tests like the at-home analysis from Hone measure both Total T and free T. Physicians analyze these biomarkers, along with others, to determine whether your hormones are balanced, but free testosterone (sometimes called bioavailable testosterone) is particularly helpful to measure, especially if you are experiencing symptoms associated with low T.
What is Total Testosterone?
Total T is the total amount of testosterone, measured in nanograms per deciliter (ng/dL) of blood, in your body. Most of the testosterone in your body is what’s called “bound,” explains family physician Nick Dahl, D.O., who treats men with low Testosterone (hypogonadism).
Total T is attached to proteins such as sex hormone binding globulin (SHBG) or albumin and is transported around your body from place to place.
It’s not usually, as Dahl says, “active.” In other words, it doesn’t have bodily effects in and of itself. Instead, this type of testosterone is metabolized into many other substances which are then used in other bodily processes, Dahl explains.
What Is Free Testosterone?
Free testosterone, on the other hand, isn’t bound to anything, so it’s free to get into cells and get to work. Free T is the type of T your body uses; it’s vital to your health. The more you have of it, the better.
KNOW YOUR T
Why You Need Free Testosterone
We tend to think of free T in an Arnold Schwarzenegger-type way: It helps you build and maintain muscle mass. But free T works in other ways, too, notes Dahl.
Free testosterone is responsible for the creation of secondary sexual characteristics in men, like facial hair and a deeper voice.
On a muscular level, free T helps muscles contract. For an organ like the heart, free T helps muscles pump more efficiently. Some research (1) suggests that men with congestive heart failure who also have low free T have poorer health prognoses. If your free testosterone levels are below normal, you might have a lower risk of clogged arteries or a heart attack, he adds.
Symptoms of low free T
Dahl also notes that people with low free testosterone levels tend to report issues with mental clarity; they feel “foggy.”
The research (3) on testosterone’s impact on the brain is unclear, but there are androgen receptors in the brain, which suggests hormones like testosterone can play a role in brain functioning.
Free Testosterone vs Total T
Ask 10 different testosterone experts what normal testosterone levels are and you might get 10 different answers, says Dahl.
Generally, though, “low” total T is thought of as anything below 300 ng/dL. “Everybody will agree that below 300 is low,” says Dahl. “But a lot of people will say that men can get benefits if you treat them up to 450 (ng/dL).”
Total Testosterone levels, and in turn, free testosterone levels (4), start to decrease around age 30 by about 1 percent every year. Genetics, your activity level, and your overall health also play a role in T levels.
Free Testosterone Range
Free testosterone levels should ideally make up between 1 to 2% of testosterone in your body. That’s why it’s hard to give an exact definition of “normal” levels without knowing someone’s lifestyle (if you’re inactive, you likely don’t need as much T as if you run marathons, for example).
The Importance of Testing Free Testosterone Levels
Since 98 percent of testosterone makes up your Total T count, some companies only test total testosterone levels. But limiting testing to just Total T has downsides.
You can have normal levels of Total T, but low levels of free testosterone says Dahl.
This is why it’s critical to test both free testosterone levels and total T, along with other biomarkers like SHBG and estrogen. It helps provide more context, says Dahl. For example, if your total T levels are not low, research finds that symptoms of low T can still exist.
Having too little free testosterone can lead to symptoms of low T like fatigue, low sex drive, erectile dysfunction, and depression (4).
Even if your total T levels are okay, your free testosterone levels could be low—and you might benefit from extra T, he says. If you only measure total T, you might miss an issue with free T.
How to Find Out if Your Free Testosterone Levels are Low
Testosterone testing (you can measure just total T or both total and free T) helps deliver results and sometimes is even used to diagnose health conditions such as ED or infertility.
Hone’s at-home hormone assessment (you do a 12-hour fast, register your test, gently prick your finger to collect a small blood sample for the necessary blood test, and send your sample back) paints a full picture of what’s going on with your T levels by measuring several biomarkers, including SHBG, estradiol, luteinizing hormone (LH), and prostate-specific antigen (PSA), and of course, both free and total T.
Treatment For Low T
Ultimately, finding out your T levels and talking with a provider about all of your symptoms is important. It helps you understand your particular circumstances, reach a diagnosis, and find a treatment plan so that you can feel better and reach your full potential day in and day out.
If your total or free testosterone levels are low, hormone replacement therapy or testosterone replacement therapy (TRT) can help. TRT replenishes your body with testosterone to combat the symptoms that are often attributable to low testosterone levels.
Testosterone is found throughout your bloodstream in two main forms: total testosterone (total T) and free testosterone (free T). Free T is the type of T your body uses but it’s important to know both numbers. If your T levels are low, testosterone replacement therapy (TRT) can help get them back within the normal range.
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1. Goodale, Travis et al. (2017) Testosterone and the Heart.
2. Vermeulen A, Goemaere S, Kaufman JM. (1999) Testosterone, body composition and aging.
3. Celec, Peter et al. (2015) On the effects of testosterone on brain behavioral functions.
4. Leen Antonio, et al (2016) Low Free Testosterone Is Associated with Hypogonadal Signs and Symptoms in Men with Normal Total Testosterone