Overview
Testosterone is a hormone that supports male sexual development, reproductive function and several other body processes. It also plays an important role in male fertility and sperm production, although testosterone levels and sperm production are not the same thing.
Table of Contents
- Introduction
- What is Testosterone?
- What Does Testosterone Do?
- How Does Your Body Produce Testosterone?
- What Are Healthy Testosterone Levels?
- What Causes Low Testosterone?
- What Symptoms Might You Notice if Testosterone Is Low?
- How Is Testosterone Tested?
- What Do Testosterone Test Results Mean?
- How Can You Support Healthy Testosterone Levels?
- Can Low Testosterone Affect Fertility?
- The Bottom Line
Introduction
Testosterone affects far more than sexual health. Its levels naturally change throughout life and can be influenced by age, sleep, body weight, stress, medications and certain health conditions. Because symptoms of hormonal changes can overlap with other health concerns, understanding the testosterone meaning can help put these changes into perspective.
Knowing what testosterone means and how it is produced can also help men understand when changes in energy, sexual health or fertility may need medical attention.
What is Testosterone?
Testosterone hormone is one of the most important regulators of reproductive and overall health. It affects fertility, muscle strength, bone density, mood and energy. Understanding how it works can help you recognise when imbalances may need attention.
It belongs to a group of hormones called androgens. Both men and women produce testosterone, but in different amounts depending on biological sex. In men, most testosterone is produced in the testicles, while women produce smaller amounts in the ovaries and adrenal glands.
What Does Testosterone Do?
Testosterone supports many essential functions in your body, including:
1. Sexual and Reproductive Function
- Supports libido (sex drive)
- Helps maintain erections
- Regulates sperm production
- Supports development of the penis and testes
2. Physical Development
- Deepens the voice during puberty
- Increase muscle mass and strength
- Encourages facial and body hair growth
- Supports bone density
3. Mood and Overall Well-being
- Influences energy levels
- Supports confidence and mental clarity
- Helps regulate mood
How Does Your Body Produce Testosterone?
Your body produces testosterone through a hormone-controlled process called the hypothalamic-pituitary-gonadal (HPG) axis.
This is how it works:
- Your body releases GnRH (gonadotropin-releasing hormone).
- This signals your pituitary gland to release LH (luteinising hormone).
- LH then stimulates your testicles to produce testosterone.
This system helps keep testosterone within a healthy range through continuous feedback signals.
What Are Healthy Testosterone Levels?
Healthy testosterone levels vary by age, biological sex and the reference ranges used by individual laboratories. The following values are commonly used by major medical organisations, including the American Urological Association (AUA):
Typical Male Testosterone Levels
| Age Group | Approximate Expected Range |
|---|---|
| Adult Men | 300-1000 ng/dL (10.4-34.7 nmol/L) |
| Men over 40 | Gradual decline of 1-2% per year |
*Values may vary by laboratory
Typical Female Testosterone Levels
| Age Group | Approximate Expected Range |
|---|---|
| Adult Women | 15-70 ng/dL |
Testosterone declines naturally with age, so doctors focus more on symptoms and patterns of low readings rather than a single number.
What Causes Low Testosterone?
Low testosterone occurs when the body does not produce enough of the hormone or when the hormonal signalling system is disrupted. Low testosterone can sometimes be associated with reduced sperm production and fertility problems, but low testosterone and male infertility are not the same condition.
Some common causes of low testosterone include:
- Age-related decline
- Testicular injury
- Hormonal disorders
- Chronic medical conditions (such as diabetes and obesity)
- Infections affecting the testicles
- Certain medications, including steroids or chemotherapy
- Excessive alcohol use
- Genetic conditions such as Klinefelter syndrome
Long-term illness, metabolic syndrome and obesity are strongly linked with low testosterone levels.
What Symptoms Might You Notice if Testosterone Is Low?
Low testosterone can cause a range of physical, sexual and emotional symptoms, depending on how low the levels are.
Some possible symptoms of low testosterone include:
- Reduced sex drive
- Low energy or fatigue
- Difficulty building or maintaining muscle
- Mood changes, including irritability
- Reduced morning erections
- Difficulty concentrating
- Increased body fat
- Lower bone density over time
- Reduced body and facial hair
- Hot flashes
You may also notice changes in fertility, as testosterone plays a key role in sperm development.
How Is Testosterone Tested?
Testosterone is tested using a blood test that measures how much of the hormone is present in your bloodstream.
Your doctor may ask you to:
- Test in the morning, when testosterone levels are naturally highest.
- Repeat the test if the result is borderline or low.
- Measure total testosterone, free testosterone or both.
These are some of the tests:
- Total Testosterone Blood Test: This is the primary test used to check testosterone levels. It measures the total amount of testosterone, including hormone bound to proteins and hormone circulating freely in the blood.
- Free Testosterone Test: Free testosterone is the portion of the hormone that is not attached to proteins. Your doctor may request this test if total testosterone results are borderline or do not fully explain your symptoms.
- Follicle-Stimulating Hormone (FSH) Test: FSH helps regulate sperm production. This test may be used to assess whether the testicles are receiving appropriate signals to support sperm and testosterone production.
- Luteinising Hormone (LH) Test: LH directly stimulates the testicles to produce testosterone. If testosterone is low but LH is high, it may indicate that the body is signalling the testicles to increase production.
A single test cannot diagnose low testosterone. Most clinical guidelines recommend at least two separate morning tests.
When Should Testosterone Be Tested?
Testosterone is usually tested when a person has symptoms that may suggest low testosterone, such as reduced sex drive, low energy, erectile difficulties or changes in body composition. The test is generally done in the early morning, when testosterone levels are typically higher.
If the first result is low, doctors usually recommend repeating the test on a separate morning before confirming testosterone deficiency. A diagnosis is based on both consistently low testosterone levels and related symptoms or signs, rather than a single blood-test result.
What Do Testosterone Test Results Mean?
Testosterone test results show whether your hormone levels fall within the expected range and help your doctor understand whether your symptoms may be related to testosterone imbalance.
Your doctor will compare your results with reference ranges and your symptoms to interpret what the numbers mean for your health.
If your testosterone level is within the expected range:
Your symptoms may be related to lifestyle factors, stress, sleep issues or other health conditions.
If your testosterone level is below the expected range:
Your doctor may investigate possible causes such as:
- Hormonal imbalances
- Thyroid function issues
- Pituitary disorders
- Sperm health (if relevant)
- Lifestyle factors affecting hormone production
Low testosterone is not diagnosed based on numbers alone; a diagnosis depends on consistently low test results along with related symptoms.
How Can You Support Healthy Testosterone Levels?
You can support healthy testosterone levels through lifestyle habits that help your body produce and regulate hormones effectively.
These steps include:
- Maintaining a healthy weight
- Exercising regularly, especially strength training
- Getting 7-9 hours of sleep each night
- Managing long-term stress
- Limiting alcohol intake
- Avoiding smoking
- Eating a balanced diet that includes protein, healthy fats and essential micronutrients
Can Low Testosterone Affect Fertility?
Yes, low testosterone can be associated with fertility problems because testosterone produced inside the testicles is important for normal sperm production. However, low testosterone does not automatically mean infertility. Male infertility can have many causes, including problems with sperm production, sperm movement, blockages, hormones or reproductive organs.
It is also important to know that taking testosterone supplements or testosterone replacement therapy while trying to conceive can reduce the body's natural sperm production and, in some men, may significantly lower or stop sperm production. Men planning a pregnancy should discuss testosterone treatment with a fertility specialist before starting it.
The Bottom Line
Testosterone is a vital hormone that supports sexual function, fertility, muscle strength, mood and overall well-being. Understanding how it works helps you recognise when changes in your energy, libido or physical health may require medical attention. If your levels are low, your doctor will identify the underlying cause, repeat tests if needed and discuss options to support your long-term health. With the right guidance, most people can manage testosterone-related changes safely and effectively.
Common Questions Asked
Does testosterone naturally decline with age?
Yes, as you age, your testosterone levels tend to decline gradually. This usually starts after your late 30s or early 40s and happens slowly over time. Not everyone experiences symptoms, which is why doctors look at both your tests and how you are feeling.
Can lifestyle habits really affect testosterone levels?
Yes. Exercise, sleep, diet and alcohol intake all influence testosterone. Small, consistent improvements can make a noticeable difference.
Can low testosterone affect fertility?
Testosterone also plays an important role in sperm production. If your levels are low and you are trying to conceive, your doctor may look at sperm health alongside hormone testing to understand the full picture.
When is the best time of the day to test testosterone?
Testosterone levels are usually highest in the morning. That’s why blood tests are often done between 7 and 10 a.m. Testing later in the day gives lower readings that don't reflect usual levels.
Do women need testosterone, too?
Even though women produce much smaller amounts, testosterone supports energy, mood, bone health and sexual well-being in women, too. Low levels can sometimes contribute to fatigue or reduced libido.
Can stress lower testosterone levels?
Yes. Chronic stress raises cortisol, which can reduce testosterone, energy and libido. Managing stress helps maintain healthy levels.