Testing Your Testosterone Levels? Know The Difference Between Free T And Total T

In men, most testosterone is made by the testes through a complex series of biochemical reactions—which convert cholesterol into testosterone (the adrenal glands also produce some testosterone).

Testosterone molecules are then secreted directly into the bloodstream—where many of them soon bind to other molecules known as sex hormone binding globulin, or SHBG (testosterone, as you may know, is a sex hormone). Other testosterone molecules bind to albumin—an important type of blood protein.

And the rest of your testosterone—the unbound testosterone? This testosterone is—quite appropriately—termed “free testosterone,” or free T, because it isn’t attached to other molecules. Because they don’t attach to other proteins, this type of bioavailable testosterone can be used up by the body. Your body actively uses free T molecules since they are at liberty to enter the body’s cells—unimpeded by SHBG or albumin—to carry out their function as signaling molecules that regulate metabolism and other cellular functions. (Testosterone molecules that are bound to other proteins cannot enter most of your cells.)

Your total testosterone level is a measure of the testosterone concentration you have in your blood in total—both free and bound. (So you’ll always have a higher level of total T than free T.)

Generally speaking, you’ll have lower levels of free T if you have more SHBG—with more SHBG molecules in your blood, a greater amount of your testosterone will be bound and not at all free.

Suppose a man was experiencing some of the symptoms of hypogonadism (a kind of androgen deficiency characterized by low testosterone)—like low libido and low energy. So he decides to measure his total testosterone levels—but discovers that his total T level is perfectly normal. Nevertheless, he’s going through very real, very debilitating symptoms of hypogonadism—so what could be the issue?

It turns out that symptoms of testosterone deficiency aren’t only caused by the total amount of testosterone in your blood. When it comes to hypogonadism, the level of free and bioavailable testosterone matters, too—because free T is what your body has readily available in the bloodstream. So you could have normal total T levels, but still suffer from symptoms of testosterone deficiency because you don’t have normal free testosterone levels (a low free testosterone concentration can be due to high SHBG levels in your blood).

Thus, your free T levels can shed light on why you may be experiencing signs of testosterone deficiency—even if your total T levels are normal. According to some research, free T levels are a better predictor of testosterone deficiency symptoms than levels of total T are. What’s more, low levels of total T don’t necessarily point to a testosterone-related health issue, since this might be simply a “side effect” of something else going on in your body.

For example, obesity can lead to a decrease in total testosterone levels since insulin resistance—a common consequence of obesity—lowers SHBG levels, causing total testosterone levels to drop, as well. However, in a scenario like this, free T is often not affected and remains at a normal level.

So while low total testosterone levels tell you that something might not be quite right with your body’s androgen hormone production, low levels of free T can help you pinpoint a possible cause of symptoms.

The Everlywell at-home total Testosterone Test is a quick and easy way to check free T levels to see how your levels compare to normal free testosterone levels for your age. Everything you need to take the test from the comfort of home is included with the kit, and you can easily view your results on our secure, online platform. If your testosterone is too low or high, talk with your healthcare provider to learn more about treatment options. Your healthcare provider might recommend testosterone replacement therapy to help get your levels back to normal.

Check Testosterone Levels At Home