Testosterone is the male hormone responsible for men's secondary sex characteristics. Bound testosterone makes up the majority, but there is also free testosterone. So, what is free testosterone? Read on to learn more about testosterone and how it works.
Testosterone is the male sex hormone in men that regulates vital functions in the body. It's responsible for giving men masculine features such as body and facial hair, muscle mass, energy, mood and sex drive.
Three main testosterone types include:
- Bound testosterone (approx 98%)
- Free testosterone (free T) (approx 2%)
- Total testosterone (total T) (combination of the two)
To understand how your body functions, it's essential to be able to distinguish between the three and learn how they work in your body. So, let's start by answering the question, what is free testosterone?
What Is Free Testosterone and Why is It Important?
Free testosterone is the unbound form of testosterone in the blood. It's the only form of testosterone that can interact with cells and have a biological effect. Several factors can affect Free T levels, including age, sex, health and medications.
In men, free testosterone influences muscle building, facial hair development, a deeper voice, metabolism and mood. Free T levels can be lower in men with certain health conditions, such as alcoholism, obesity and diabetes (1). Medications that can lower free T levels include cancer treatments and anti-androgens. (2)
Free testosterone levels are essential for many bodily functions, (3) including:
- Sex drive
- Sperm production
- Bone health
- Muscle mass
- Fat distribution
- Mood
- Energy levels
Low free testosterone levels can cause a variety of symptoms (4), including:
- Low sex drive
- Erectile dysfunction
- Fatigue
- Depression
- Loss of muscle mass
- Increased body fat
- Hot flashes
- Night sweats
What is Total Testosterone?
Total testosterone includes both bound and unbound testosterone. A simple blood test is available to show total testosterone levels and can pinpoint whether you have low testosterone. It measures the blood in the body in nanograms per deciliter (ng/dL).
Most of the body's testosterone binds to sex hormone-binding globulin (SHBG) or other proteins and is commonly called 'bound testosterone.'
What Are Free Testosterone Levels?
Free T is the percentage of total testosterone unattached to proteins, such as sex hormone-binding globulin (SHBG) or albumin, and is bioavailable for the body's tissues to use. Unlike total testosterone levels, which measure both bound and unbound testosterone, free testosterone levels indicate the amount readily available for biological activity.
While numbers can have their place, symptoms are vital in determining free testosterone levels because they provide valuable insights into an individual's potential hormonal imbalances and overall health. (5)
Symptoms associated with testosterone deficiency or excess can explain the possible imbalance in free testosterone levels. Some common symptoms of low free testosterone include:
- Reduced libido or sexual desire
- Erectile dysfunction or difficulty achieving/maintaining an erection
- Fatigue or decreased energy levels
- Loss of muscle mass or strength
- Decreased bone density
- Mood changes, such as depression or irritability
- Increased body fat, particularly around the abdomen
- Hair loss or thinning
- Difficulty concentrating or decreased cognitive function
On the other hand, symptoms of high free testosterone may include:
- Increased libido or sex drive (hyper-sexuality)
- Acne or oily skin
- Aggressive or irritable behavior
- Rapid muscle gain or increased strength
Symptoms can vary depending on individual circumstances and are essential in determining when hormone level testing is necessary.
Free Testosterone vs. Total Testosterone
As discussed, free testosterone and total testosterone are necessary measures of testosterone levels in the body. Still, they represent different aspects of testosterone bioavailability.
The ratio of free testosterone to total testosterone is essential in assessing testosterone status. While total testosterone levels can give a general indication of testosterone production, free testosterone levels provide a more accurate measure of the testosterone that is actively available for physiological functions.
It's important to understand that the reference ranges for total and free testosterone can vary. Individual factors such as age, sex, and underlying health conditions can influence testosterone levels. Therefore, it's crucial to interpret the results in the context of an individual's specific circumstances and symptoms and not rely solely on numbers.
What Is a Testosterone Levels Test?
A testosterone levels test, also known as a testosterone blood test, is a medical test used to measure the amount of testosterone hormone in a person's bloodstream. Testosterone levels vary significantly from one person to another, and there is no reliable average testosterone level to use as a basis. Symptoms are the most reliable tool for diagnosis. However, the test is commonly ordered to evaluate testosterone levels for various reasons, such as:
- Assessing Hormonal Imbalances: It helps determine if testosterone production is abnormal.
- Investigating Symptoms: The test may be used to investigate symptoms related to testosterone imbalances, such as low sex drive, infertility, erectile dysfunction, excessive facial or body hair growth, or other signs of hormone-related disorders.
- Monitoring Hormone Replacement Therapy: For individuals undergoing testosterone replacement therapy, regular testosterone tests may be performed to monitor hormone levels and ensure the treatment is effectively restoring testosterone to the desired range.
Venous Blood Draw For Testosterone
The test typically involves a simple blood test, usually from a vein in the arm. Testosterone levels can vary throughout the day, so the test is often done in the morning when testosterone levels are highest. These tests must be performed in a clinic or by a medical professional in your home.
At-Home Blood Spot Test For Testosterone
Many clinics, like us, now use at-home finger prick test kits, which are far easier and less painful than a blood draw. These clever little At-Home Testosterone Tests contain a small lancet used to prick your fingertip, and tiny droplets of blood are 'milked' onto a test sheet with small circles to fill. They can be sent through the mail and offer accurate results for all the same biomarkers as a traditional blood draw.
It's important to note that interpreting testosterone levels requires considering the individual's age, sex, and any specific symptoms or medical conditions present. Testosterone levels can fluctuate naturally, and the results should be interpreted in the context of the person's overall symptoms, health and medical history.
Conclusion
Testosterone naturally declines as we age and can cause adverse symptoms affecting energy levels, sex drive and body fat. While total testosterone levels are important, free T is the type of testosterone your body has readily available for biological activity. If you have symptoms of low testosterone, testosterone replacement therapy can make a difference in how you feel.
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