Everything You Need to Know About Low Testosterone Levels

Low testosterone levels can affect sexual health, energy, mood, muscle strength, and fertility. Testosterone is an important hormone that supports male reproductive development and several functions throughout adulthood. When levels are consistently lower than expected, some men develop symptoms that may indicate testosterone deficiency, also called male hypogonadism.

However, fatigue, reduced sex drive, erectile difficulties, and changes in body composition can have many causes. Symptoms alone cannot confirm low testosterone. Diagnosis usually requires a clinical assessment and blood tests, with treatment based on the underlying cause, symptoms, and individual health needs.

What Are Low Testosterone Levels?

Testosterone is the primary male sex hormone, produced mainly by the testicles. The hypothalamus and pituitary gland in the brain help regulate its production through hormonal signals.

Low testosterone levels occur when the body produces insufficient testosterone or when hormone levels remain below the expected range in a person who has compatible symptoms or clinical signs. This condition is commonly known as testosterone deficiency or male hypogonadism.

Testosterone levels vary between individuals and can fluctuate throughout the day. A result below a laboratory’s reference range does not automatically mean that treatment is necessary.

What Does Testosterone Do in the Body?

Testosterone contributes to several important functions, including:

• Development of male reproductive organs and secondary sexual characteristics.
• Sexual desire and aspects of erectile and sexual function.
• Sperm production, together with other reproductive hormones.
• Maintenance of muscle mass, strength, and bone density.
• Red blood cell production.
• Distribution of body fat.
• Support for mood, motivation, and general well-being.

Testosterone is important throughout life, although its effects differ depending on age and stage of development. In adults, persistently low levels can affect several body systems, but the symptoms and severity vary.

What Is Testosterone Deficiency?

Testosterone deficiency, or hypogonadism, is a medical condition in which testosterone production or function is inadequate.

There are two main types:

• Primary hypogonadism: The testicles do not produce sufficient testosterone, sometimes because of genetic conditions, injury, infection, or medical treatment that affects testicular function.
• Secondary hypogonadism: The hypothalamus or pituitary gland does not provide the hormonal signals needed for normal testosterone production.

Some people have a combination of contributing factors. Identifying the type can help clinicians determine the cause and choose an appropriate treatment.

Read Also: How To Treat High Testosterone In Males

Do Testosterone Levels Change With Age?

Testosterone levels often decrease gradually as men get older, but the pattern varies considerably. Age alone does not establish a diagnosis of testosterone deficiency.

Some older men maintain testosterone levels within the expected range, while younger men can develop low levels because of medical conditions, medications, obesity, or problems affecting the testicles or pituitary gland.

A diagnosis should be based on symptoms, clinical findings, and appropriately interpreted blood tests rather than age alone.

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What Are the Symptoms of Low Testosterone?

The symptoms of low testosterone can develop gradually and may be difficult to distinguish from other health problems. Some men experience sexual symptoms, while others notice changes in energy, mood, physical strength, or fertility.

Common symptoms and signs include:

• Reduced sexual desire or interest in sex.
• Fewer spontaneous or morning erections.
• Erectile difficulties.
• Persistent fatigue or reduced energy.
• Decreased muscle mass or strength.
• Increased body fat.
• Low mood, irritability, or reduced motivation.
• Difficulty concentrating.
• Reduced bone density or unexplained fractures.
• Reduced sperm production or infertility.

Not everyone with low testosterone experiences all these symptoms. Their presence also does not necessarily mean testosterone is low.

Sexual Symptoms and Reduced Libido

A reduction in sexual desire is one of the symptoms more closely associated with testosterone deficiency. Some men also notice fewer spontaneous erections or changes in sexual function.

Testosterone plays a role in sexual interest, but erections depend on several systems working together, including blood flow, nerve function, psychological factors, and overall health.

Low testosterone can contribute to erectile dysfunction (ED), but it is not the only possible cause. Conditions such as diabetes, cardiovascular disease, anxiety, medication side effects, and hormonal disorders may also affect erections.

A clinician can assess whether testosterone testing is appropriate and whether other causes need investigation.

Physical Symptoms and Changes in Body Composition

Persistently low testosterone may contribute to reduced muscle mass, lower muscle strength, and an increase in body fat. Some men may also develop reduced bone density over time.

These changes are not specific to testosterone deficiency. Physical inactivity, ageing, inadequate nutrition, chronic illness, and other hormonal conditions can produce similar effects.

Unexplained loss of muscle strength, low bone density, or recurring fractures may warrant medical evaluation, particularly when other symptoms are present.

Mood, Energy, and Cognitive Symptoms

Some men with low testosterone report fatigue, reduced motivation, low mood, irritability, or difficulty concentrating.

However, these symptoms are common in many conditions, including depression, sleep disorders, anaemia, thyroid problems, and chronic stress. Poor sleep and certain illnesses can also affect testosterone levels, making the relationship more complicated.

Persistent fatigue or changes in mood should not automatically be attributed to testosterone. A broader assessment can help identify treatable causes.

Fertility and Reproductive Symptoms

Testosterone is necessary for normal male reproductive function, but sperm production depends on signals from the pituitary gland, particularly luteinising hormone (LH) and follicle-stimulating hormone (FSH).

Low testosterone may occur alongside impaired sperm production, reduced testicular function, or infertility. However, a normal testosterone result does not guarantee normal fertility, and a low result does not establish the cause of infertility.

Men experiencing difficulty conceiving may need a reproductive assessment that includes a semen analysis and appropriate hormone tests.

What Causes Low Testosterone Levels?

Low testosterone can result from problems affecting the testicles, the brain’s hormonal control system, general health, or medication use. In some cases, several factors contribute at the same time.

Age-Related Hormonal Changes

Testosterone production can decline gradually with age. The extent of this change varies between individuals and may be influenced by body composition, sleep quality, chronic illnesses, and medication use.

Age-related changes do not automatically require testosterone treatment. Clinicians assess whether symptoms and consistently low hormone levels indicate a medical condition that may benefit from intervention.

Testicular Conditions and Injuries

The testicles produce most of the testosterone in adult men. Conditions that damage testicular tissue or interfere with its function may reduce hormone production.

Possible causes include:

• Genetic conditions that affect testicular development.
• Testicular injury or certain infections.
• Previous chemotherapy or radiation treatment.
• Surgery affecting the testicles.
• Undescended testicles or other developmental problems.

The effect depends on the condition and the extent of damage. Medical evaluation can help determine whether the problem is related to primary hypogonadism.

Pituitary and Hypothalamic Disorders

The hypothalamus and pituitary gland regulate testosterone production by sending hormonal signals to the testicles.

Disorders affecting these structures may reduce the release of gonadotropin-releasing hormone, LH, or FSH. Potential causes include pituitary tumours, certain genetic conditions, head injuries, and other neurological or hormonal disorders.

When low testosterone is associated with low or inappropriately normal LH and FSH levels, further testing may be needed to investigate secondary hypogonadism.

Obesity, Chronic Illness, and Sleep Problems

Obesity is associated with lower testosterone levels in some men. Excess body fat and related metabolic changes can influence hormone regulation, while chronic illnesses may also affect testosterone production.

Potential contributing factors include:

• Obesity and metabolic disorders.
• Type 2 diabetes.
• Significant or prolonged illness.
• Obstructive sleep apnoea and poor sleep.
• Inadequate nutrition or substantial calorie restriction.
• Excessive physical stress associated with inadequate recovery.

In some cases, low testosterone may improve when an underlying problem is treated. However, improvement is not guaranteed, and persistent symptoms may require further assessment.

Medicines and Anabolic Steroid Use

Certain medicines can interfere with testosterone production or hormonal regulation. Examples include opioid pain medicines and some treatments that affect the pituitary gland or reproductive hormones.

Anabolic steroid use can also suppress the body’s natural testosterone production. After stopping these substances, hormone recovery may take time and may not be complete in every case.

Do not stop prescribed medication or attempt to correct hormone levels with unregulated products without medical guidance. A clinician can review potential medication effects and discuss safer alternatives when appropriate.

What Are Normal Testosterone Levels?

There is no single testosterone value that can be interpreted in isolation for every person. Results depend on the laboratory method, reference range, age, clinical context, and whether total or free testosterone is measured.

For adult men, a total testosterone concentration below approximately 300 ng/dL (about 10.4 nmol/L) is commonly used as a threshold supporting further evaluation. It is not a universal diagnostic rule, and a low result alone does not confirm testosterone deficiency.

Understanding Total and Free Testosterone

Blood tests may measure total testosterone or assess free testosterone when clinically indicated.

• Total testosterone: Measures testosterone circulating in the blood, including hormone bound to proteins and the unbound fraction.
• Free testosterone: Refers to the small portion that is not bound to blood proteins and is available to tissues.
• Sex hormone-binding globulin (SHBG): A protein that binds testosterone and affects how total testosterone relates to free testosterone.

Changes in SHBG can make total testosterone harder to interpret. When a result is borderline or a condition may alter SHBG, a clinician may request free testosterone testing using an appropriate laboratory method or calculation.

How Age and Testing Conditions Affect Results

Testosterone concentrations typically fluctuate throughout the day and are often highest in the morning. Food intake, acute illness, sleep disruption, and other factors can also influence results.

For these reasons, testing is generally performed in the morning, often while fasting, according to the clinician’s instructions. If someone is acutely unwell, testing may need to be repeated after recovery.

Results should be interpreted using the reference range and testing method provided by the laboratory.

Why One Low Test Result May Not Be Enough

A single low result may reflect normal biological variation, temporary illness, or testing conditions rather than persistent testosterone deficiency.

Clinicians generally confirm a low result with a second morning measurement on a separate day. The diagnosis also requires compatible symptoms or clinical signs and consideration of other possible explanations.

This approach helps reduce the risk of unnecessary treatment and makes it easier to identify men who genuinely need further evaluation.

How Is Low Testosterone Diagnosed?

Diagnosis involves reviewing symptoms, medical history, medicines, physical findings, and laboratory results. Testing is usually appropriate when a person has symptoms or signs that suggest testosterone deficiency rather than as routine screening for every asymptomatic man.

Morning Testosterone Blood Tests

The initial investigation is generally a blood test measuring total testosterone. It is usually collected in the morning, with fasting recommended in many clinical guidelines.

If the result is low, the clinician will usually arrange a repeat test on another morning before confirming the diagnosis.

The clinician may also ask about:

• Changes in sexual desire or erectile function.
• Fertility goals.
• Sleep patterns and energy levels.
• Current medicines and previous anabolic steroid use.
• Chronic medical conditions.
• Previous testicular injury, surgery, or cancer treatment.

These details help place the laboratory results in context.

Why Repeat Testing May Be Needed

Testosterone levels can vary between days. A temporary reduction may occur during acute illness or because of other factors affecting the body.

Repeating the test helps establish whether the level is consistently low. A diagnosis should not be based solely on a symptom checklist, an online questionnaire, or one isolated laboratory value.

Additional Tests to Identify the Cause

If low testosterone is confirmed, additional investigations may be needed to determine why it is occurring. Depending on the findings, these may include:

• LH and FSH: Help distinguish testicular problems from issues involving the pituitary or hypothalamus.
• Prolactin: May be measured when a pituitary-related cause is suspected.
• Free testosterone and SHBG: May help clarify borderline or difficult-to-interpret total testosterone results.
• Other blood tests: Thyroid function, blood count, glucose, or other investigations may be appropriate based on symptoms and medical history.
• Imaging: Pituitary imaging may be considered when hormone results or symptoms suggest a pituitary disorder.

Not everyone needs every test. The investigation plan depends on the suspected cause and individual clinical findings.

How Are Low Testosterone Levels Treated?

Treatment depends on the underlying cause, the severity of symptoms, hormone test results, fertility plans, and overall health. Some men may benefit from addressing contributing health conditions, while others with confirmed testosterone deficiency may be considered for testosterone replacement therapy.

Treatment should be guided by a qualified healthcare professional rather than started solely because of fatigue, ageing, or a single low test result.

Treating the Underlying Cause

When a reversible factor contributes to low testosterone, addressing it may improve hormone levels or related symptoms.

Examples include managing obesity, improving sleep when appropriate, treating an underlying illness, reviewing medicines that may affect hormone production, or receiving specialist care for a hormonal disorder.

The result depends on the cause. Lifestyle changes and treatment of related conditions do not replace a medical assessment when testosterone deficiency is suspected.

Testosterone Replacement Therapy

Testosterone replacement therapy (TRT) uses prescribed testosterone to restore levels in men with an established deficiency when treatment is appropriate.

Potential benefits may include improvements in sexual desire, certain symptoms of hypogonadism, and bone or body composition measures. The degree of benefit varies, and not every symptom improves with treatment.

TRT is not intended as a general anti-ageing treatment, a bodybuilding aid, or a routine method for increasing energy in men whose testosterone levels are normal.

Before treatment begins, the clinician should discuss expected benefits, potential risks, fertility goals, alternatives, and the monitoring required.

Gels, Injections, and Other Formulations

Prescription testosterone is available in several formulations, depending on the country and product availability.

Common options include:

• Topical gels: Applied to the skin as directed. Transfer to another person through skin contact is an important safety consideration.
• Injections: Administered at prescribed intervals, which vary by formulation.
• Patches: Deliver testosterone through the skin and may cause local irritation.
• Other formulations: Certain regions have additional approved options, such as oral or implantable preparations.

Each formulation has different dosing schedules, practical considerations, and potential adverse effects. The choice should be individualised, and the prescribed dose should not be changed without medical advice.

Who May Benefit From Treatment?

TRT may be considered for men who have compatible symptoms or signs and consistently low testosterone confirmed by appropriate testing, particularly when a treatable hormonal deficiency has been established.

It may not be appropriate for everyone. For example, external testosterone can suppress sperm production, so it is generally not recommended for men who are planning fertility in the near term.

Other conditions, including certain prostate or breast cancers, elevated red blood cell levels, untreated severe obstructive sleep apnoea, and some cardiovascular or clotting problems, may affect whether treatment can be started safely.

A clinician should assess these factors before prescribing therapy.

What Are the Risks and Side Effects of Testosterone Therapy?

Testosterone therapy can be beneficial for appropriately selected patients, but it also carries risks. The likelihood and severity of side effects depend on the formulation, dose, individual health, and monitoring.

Effects on Fertility and Sperm Production

One of the most important considerations is fertility. Testosterone taken from an external source can suppress LH and FSH signalling, reducing the testicles’ own testosterone production and sperm production.

This may lead to a substantial reduction in sperm count and, in some cases, infertility during treatment. Recovery after stopping testosterone can take months or longer and is not always predictable.

Men who want to conceive should discuss this before starting treatment. A fertility specialist or endocrinologist may consider alternative approaches, depending on the cause of the hormone deficiency.

Red Blood Cell Count and Other Potential Side Effects

Potential adverse effects of TRT include:

• Increased red blood cell count or haematocrit.
• Acne or oily skin.
• Fluid retention.
• Breast tenderness in some patients.
• Reduced sperm production and testicular shrinkage.
• Skin irritation from topical formulations.
• Worsening of certain urinary symptoms in susceptible individuals.

Testosterone therapy may also require particular caution in men with untreated severe sleep apnoea or specific cardiovascular, prostate, or clotting-related conditions. Its overall benefits and risks need to be assessed individually.

Monitoring During Treatment

Men receiving TRT generally need regular follow-up to check whether treatment is helping and whether side effects are developing.

Monitoring may include:

• Testosterone levels to assess whether the prescribed treatment is achieving the intended range.
• Complete blood count or haematocrit to detect excessive increases in red blood cells.
• Assessment of symptoms and adverse effects.
• Prostate health assessment when appropriate for the individual’s age and risk.
• Review of blood pressure, sleep-related symptoms, and other health concerns as clinically indicated.

Monitoring schedules vary depending on the patient and formulation. Follow-up is an essential part of treatment, not an optional extra.

Can Lifestyle Changes Help Support Healthy Testosterone Levels?

Lifestyle measures can support general health and may improve testosterone levels in some men, particularly when low levels are associated with obesity, inadequate sleep, or other modifiable factors. They cannot correct every cause of testosterone deficiency.

Maintaining a Healthy Weight

For men with excess body fat, gradual weight loss may improve hormonal and metabolic health. A sustainable approach usually includes balanced eating, regular physical activity, and adequate sleep.

However, unexplained low testosterone should not automatically be attributed to body weight. Medical assessment may still be needed to identify other causes.

Exercise, Sleep, and Stress Management

Regular physical activity supports cardiovascular health, muscle function, and general well-being. Resistance training can help maintain muscle mass, while aerobic exercise supports overall fitness.

Adequate sleep is also important. Persistent sleep deprivation and untreated sleep disorders may affect hormonal regulation and energy levels.

Useful habits include:

• Maintaining a consistent sleep schedule.
• Getting regular aerobic and resistance exercise suited to your health.
• Allowing adequate recovery between demanding workouts.
• Seeking assessment for symptoms of sleep apnoea.
• Using practical stress-management strategies.

These habits support health but do not guarantee that testosterone levels will return to a particular range.

Nutrition and Alcohol Use

A balanced diet with sufficient energy, protein, healthy fats, vitamins, and minerals supports normal bodily function. Severe calorie restriction and nutritional deficiencies can interfere with reproductive hormone regulation.

Excessive alcohol use can harm general and reproductive health, so reducing heavy consumption may be beneficial.

Be cautious with products marketed as testosterone boosters. Evidence for many such supplements is limited, and some products may contain undisclosed ingredients or interact with medicines. Supplements should not replace proper testing or prescribed treatment.

Frequently Asked Questions

Conclusion

Low testosterone levels can affect sexual desire, energy, muscle mass, bone health, mood, and reproductive function. However, these symptoms have many possible causes, so they should not be used alone to diagnose testosterone deficiency.

Accurate assessment usually involves a clinical review and repeat morning blood tests, followed by additional investigations when needed. Treatment depends on the cause and may involve managing underlying conditions or considering testosterone replacement therapy in appropriately selected men.

Anyone experiencing persistent symptoms should seek medical evaluation rather than self-diagnosing or using unregulated testosterone products. Men considering treatment should discuss potential benefits, risks, fertility plans, and follow-up requirements with a qualified healthcare professional.

References

• Endocrine Society
• American Urological Association
• MedlinePlus