Free Testosterone vs. Total Testosterone: Which One's More Important?

Testosterone is a sex hormone that’s affected by the male aging process. But not all testosterone is equal. Some of the most important players are free testosterone and total testosterone — lab variables that are checked by your healthcare provider in order to verify whether or not you might be testosterone deficient.

Testosterone is an important factor in men’s reproductive health and can impact an array of medical conditions. Doctors recommend checking your testosterone regularly after the age of 35 as testosterone levels tend to decline as we age.

For a blood draw, your physician will request for you to come in early in the morning — when your testosterone level is at its highest. Your levels naturally fluctuate throughout the day and plummet in the evenings. That’s why it’s imperative your blood is drawn during “peak hours.”

What happens next and which lab variables are more important, free or total testosterone? Let’s find out.

Why is Testosterone Even Important?

As a hormone, testosterone supports men’s health in many ways. But what are hormones in the first place? They are chemical messengers that move around within your body, traveling to organs and tissues, so they can complete their designated tasks.

Testosterone, in particular, is a critical part of regulating your muscle mass, libido, and bone density. It further helps distribute fat within your body and supports the production of both sperm and red blood cells. 

According to the Urology Care Foundation, not having enough testosterone can further cause you to feel drained and fatigued, affect your energy levels, and trigger mood swings and depression. It can also lead to obesity, which encompasses an array of new medical problems.

With such a multi-faceted reach, testosterone is one of the most important hormones affecting men’s health.

Free Testosterone vs. Total Testosterone: What’s What?

Based on your age and symptoms, and whether you’ve been diagnosed with hypogonadism, your healthcare provider may order a testosterone lab test for you. The two utmost important variables that he will check are free testosterone and total testosterone.

While testosterone samples can be collected through your saliva, it’s much more common and reliable to use blood samples to determine your testosterone levels. Measured in ng/dL (nanograms per deciliter), your lab report will list both FRTST and TTST: free testosterone and total testosterone respectively — both of which are determined through serum blood.

But what does free and total testosterone stand for and how are the two different?

Free testosterone is the testosterone that’s not attached to any proteins — it’s hence “free” and can easily be used for bodily functions. Testosterone can, however, attach to two proteins: albumin and sex hormone-binding globulin (SHBG). 

Since FRTST doesn’t attach to either protein, it’s known as bioavailable testosterone alongside albumin-bound testosterone — which is only loosely bound and can easily be disconnected.

Free testosterone is also referred to as active testosterone and ranges from 4.5 to 25 ng/dL in healthy males. It makes up about 2 to 3% of the total testosterone in your blood.

The other value, total testosterone, encompasses all of the free testosterone, plus any testosterone bound to protein. It’s, therefore, the “total” amount of testosterone present per deciliter serum blood. Total testosterone normal values range between 300 and 800 ng/dL.

The majority of your total testosterone constitutes protein-bound testosterone, with roughly 60% bound to sex hormone-binding globulin (SHBG) and 50% attached to albumin. Free testosterone makes up only a small portion of the overall testosterone in your blood.

Are There Other Types of Testosterone?

Besides total and free testosterone, there is protein-bound testosterone, which comprises two types of testosterone — one that binds to albumin and one that attaches to sex hormone-binding globulin (SHBG). Together they make up the majority of testosterone in your bloodstream.

SHBG and albumin are proteins and testosterone bound to either one of them remains biologically inactive. Albumin and SHBG are produced by your liver and can transport testosterone throughout your body after it attaches to their receptors.

SHBG changes with age and can be further impacted by liver disease, obesity, and an overactive thyroid. The amount of SHBG in your bloodstream is significant as it helps regulate how much testosterone can be used by your tissues.

Another form of testosterone, dihydrotestosterone, also known as DHT is “converted” testosterone, which binds to SHGB. It plays a particularly important role in regulating prostate size and developing certain male features.

Which One is More Important: Free Testosterone or Total Testosterone?

Both your total and free testosterone are critical contributors to your health — they simply have different roles. Total testosterone will give you an overview of your testosterone levels: a summary of all active and inactive testosterone in your body. 

Free testosterone, on the other hand, offers you a screenshot of one type of testosterone, in particular. When your physician suspects that your SHGB-binding testosterone is potentially lowered, your total testosterone may be falsely reduced, which can be very misleading. In instances like this, the free testosterone can help provide more clarity.

Yet, if your free testosterone levels are low, it might not show up in the value provided by your total testosterone. As the active form of testosterone, however, low free testosterone can quickly lead to symptoms, so your provider will know to check both values.

Knowing where your free testosterone stands can be very helpful as it’s considered a valuable gauge of good health and marks the testosterone portion your body actively uses.

Make Sure to Keep Your Testosterone Levels Checked 

Checking your testosterone levels regularly and maintaining a healthy lifestyle are crucial factors for your well-being. This is especially important as testosterone levels begin to gradually drop when you’re in your 30s and naturally decline with growing age.

It’s easy for your healthcare provider to order a simple blood test and determine where your free and total testosterone is at. If you’re feeling fatigued, notice a lowered sex drive, or begin feeling depressed, know that these can be signs of low testosterone and may need to be addressed.

Learn more about the different types of testosterone and everything you need to know about testosterone deficiency. Sign up for our newsletter here and keep learning.

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