The hormone that ensures human life and is one of the most essential androgens (a steroid hormone that regulates male development and maintenance) present in both men’s and women’s bodies. This hormone is testosterone.
When it comes to testosterone, there are two main types that are looked at: free testosterone and total testosterone. The free testosterone is the “unbound” version, and the total testosterone is the “bound” and “unbound” versions combined.
It has a rather technical meaning: it indicates that it is free and not connected to anything.
Non-SHBG bound testosterone is also sometimes referred to as bioavailable testosterone.
Due to testosterone being the primary male sex hormone, men who have a testosterone deficiency most commonly express having decreased strength, erectile dysfunction, loss of muscle mass, and low libido.
After speaking with a doctor, they will confirm low testosterone levels by measuring their total testosterone. But the true issue at hand is free testosterone levels. This can be easily treated with testosterone replacement therapy (TRT).
Let’s explore free testosterone and total testosterone and why it is important to understand the difference between each.
- Testosterone floats through our body “bound” to either SHBG or albumin
- Free testosterone is the “unbound” version, and the total testosterone is the “bound” and “unbound” versions combined
- Total testosterone levels are important when it comes to treatment for hypogonadism and monitoring testosterone replacement therapy (TRT)
- Understanding the difference between free testosterone and total testosterone can help ensure that you are getting the appropriate treatment for low testosterone levels
Testosterone is the primary sex-hormone (androgen) that is produced by what is known as Leydig cells of the testes. It is what gives men their beards, deepened voice, and increased muscularity compared to females.
It is also responsible for triggering the beginning of puberty in young boys. This is all done through a process known as androgenization, where testosterone begins to affect the various parts of the body that it will impact.
In men, testosterone circulates throughout the body in the blood. When testosterone is floating around the body, it is attached to different proteins. These include:
Sex hormone-binding globulin (SHBG)
The sex hormone-binding globulin is a protein that testosterone binds to for a short period of time. It does two things: it regulates the amount of unbound testosterone in the body and ensures that too much testosterone isn’t produced.
Albumin is the most common protein in human blood plasma. It’s also where the bulk of your free testosterone will attach. Because testosterone is weakly bound to albumin, it can roam through the body easily and detach as needed to do its job.
Non-SHBG bound testosterone is sometimes also said to be “bioavailable” testosterone.
Free Testosterone vs Total Testosterone: What the Heck is The Difference?
You’re probably wondering what your blood tests mean when you see “Free testosterone” and “total Testosterone”. So, let’s talk about it.
For one, majority of testosterone in our bodies is bound to something –approximately 98%. Of the testosterone that is bound, 40% is attached to SHBG and the remaining 60% to albumin. The other 2%, however, remains unbound and free-floating. This sort of testosterone, which we call “free,” has no connection to anything, such as a protein, so that it works freely to influence the body and mind.
Hence, because this testosterone is unbound, it circulates through the body more easily and is available for use by the body.
The benefits often attributed to higher testosterone levels (heightened sex-drive, increased energy levels, chiseled body) are more closely associated with free testosterone. As a result, it’s important to find out what your free testosterone levels are.
When your doctor orders a blood test to measure serum testosterone levels, often times they are measuring your total testosterone levels.
As the name implies, this is the total amount of testosterone in your body, both free and bound. This means the sum of all testosterone in your body, both free and bound (remember it is either SHBG-bound or albumin-bound).
While it’s not as essential to know your total testosterone levels, knowing them might help your doctor determine whether your testosterone levels are too high, too low, or if you have hypogonadism, infertility, sexual dysfunction, pituitary gland disorders, adrenal glands issues, or a tumor.
For men that are currently on testosterone replacement therapy, measuring total testosterone is the best way to ensure that your testosterone levels are where they should be.
To sum it up: free testosterone is the most important and bioavailable and free testosterone form in the body, while total testosterone is the sum of free and bound testosterone in the body.
Do I test Total or Free Testosterone?
For many years now, total testosterone has been the primary measurement of testosterone used by doctors. However, free testosterone is becoming increasingly popular as further studies confirm the importance of free testosterone .
For example, measuring total testosterone is useful when measuring for hypogonadism, infertility, and monitoring men on testosterone replacement therapy.  But, because this measures the entire lot (keep in mind that around 98% of testosterone is bound), it may miss other issues, such as excessively tight bonding of testosterone to SHBG or albumin. As a result, it would not measure the amount of free testosterone in circulation.
Recent studies that connect testosterone levels with age have been conducted. What they found was that men with lower free testosterone levels were more prone to memory issues and had a much higher likelihood of developing Alzheimer’s disease as they age. 
On the other hand, free testosterone levels did not have as strong of a correlation to memory issues.
What this means is that, free testosterone may be a better predictor of age-related issues and diseases than total testosterone. As such, testing for both total testosterone and free testosterone is becoming the more routine way of measuring testosterone by most doctors.
However, to date, there has been no well designed study that indicates measuring one versus the other is better. It truly depends on a variety of things such as what you are being tested for, your symptoms, age, and other factors.
Therefore, it is best to discuss with your doctor your symptoms and concerns.
How to treat Low Testosterone
When your doctor confirms that your symptoms are a result of having low testosterone, you will likely be put on testosterone replacement therapy (TRT).
Testosterone replacement therapy can offer many satisfying benefits, such as increased sex-drive, better memory, increased energy, more muscle mass, and a lot more.
But the only way to get back on the right track to being the best version of yourself is to speak with your doctor and get your testosterone levels checked.