“Total” vs. “Free” Testosterone: What’s the Difference?
Testosterone is a vital hormone for both men and women. Most of the testosterone in the bloodstream is bound to two proteins: albumin and sex hormone-binding globulin (SHBG).
There is however some testosterone in the blood that is not attached to these proteins, this is what is referred to as “free testosterone.”
The total of both your protein-bound testosterone and free testosterone is known as “bio-available testosterone.” While both bound and free testosterone is available, it is only the free that is immediately accessible for use by your body.
The molecules of free testosterone can be immediately used by your body because they can simply enter the cells unimpeded by being unattached to SHBG or albumin. The bound testosterone is more like a reserve tank on a car.
Why Does It Matter to Know the Difference Between “Total” and “Free” Testosterone?
If you are suffering from the symptoms of low testosterone, most of the time your doctor will only test for your total testosterone. In most cases, a test for total testosterone is enough for a doctor to make a diagnosis of low testosterone (Low-T).
However, there are men who may be suffering from the typical symptoms of Low-T – low libido, weight gain, brain fog, and constant low energy – whose total testosterone test comes back perfectly normal. Yet, he’s still going through the very real and very debilitating symptoms of low testosterone –so what could be the issue?
As it turns out, the symptoms of Low-T aren’t only caused by the total amount of testosterone in your blood. When it comes to low testosterone, the level of your free testosterone may be just as important as your total bio-available testosterone. This is because it is the free testosterone that is readily available in the bloodstream.
If your test for total testosterone comes back normal, it could be that a disproportionate amount of your testosterone is “locked up” as bound testosterone. Following up with a test for free testosterone can give your doctor a more accurate picture as to why you may be exhibiting the signs of low testosterone, even when your total testosterone levels appear to be in the normal range.
Current research seems to suggest that your level of free testosterone can be a better diagnostic tool for evaluating your symptoms of low testosterone than are your levels of total testosterone.
Your levels of both your free and total testosterone decrease as you age
The following table illustrates the range of normal “free” testosterone for men and women by age.
|Gender/Age (y)||Range (pg/mL)|
|0 to 19||Not established|
|20 to 29||9.3−26.5|
|30 to 39||8.7−25.1|
|40 to 49||6.8−21.5|
|50 to 59||7.2−24.0|
|0 to 19||Not established|
Source: LabCorp (FREE T)
How Can I Increase My Free Testosterone Levels?
If after testing either your total testosterone and/or your free testosterone, it is determined that your testosterone levels are below normal, you may be a candidate for testosterone replacement therapy.
For men diagnosed with low testosterone – either by their free or total testosterone levels – testosterone replacement therapy can offer a lot of benefits. One of the most satisfying benefits of testosterone therapy is an increased sex drive and improved sexual performance. Some of the other benefits of testosterone therapy for men include:
Testosterone therapy can make you feel younger, stronger, and improve your confidence, so you can continue to do all the things you enjoy most in life. But the only way to be sure if you need a prescription for testosterone replacement is to have your symptoms evaluated, and your blood tested.