Causes of low testosterone in young men

Do you often feel persistently fatigued, lack motivation, or simply not like yourself? While stress and a busy lifestyle are common suspects, the underlying cause for some young men may be low testosterone. Although testosterone deficiency is often considered an issue that arises later in life, it can occur much earlier and have a significant impact on energy levels, mood, muscle development and even fertility. It is therefore essential to understand the role of testosterone, recognise the signs of deficiency, and know how to address it, in order to maintain long-term health and wellbeing.

Table of Contents

• What is testosterone and why is it important?
• What are normal testosterone levels?
• Common causes of low testosterone in young men
• Signs and symptoms of low testosterone
• When to see a doctor
• Tips for supporting healthy testosterone levels
• Frequently asked questions
• Summary

Research on low testosterone in young men is limited in Europe, but available data show it is not uncommon. About 2% of men overall have low testosterone, with prevalence rising to over 8% in those aged 50-79 (Cleveland Clinic, 2022). U.S. data from more than 4,000 men aged 15-39 found that around 20% had testosterone deficiency, with average levels declining sharply between 1999 and 2016 (Patel, P., et al., 2020). Although exact figures for the Netherlands and Germany are lacking, these findings show that low testosterone can affect men of all ages, including younger men with certain risk factors.

What is testosterone and why is it important?

Testosterone is a sex hormone, produced mainly in the testes in men and in smaller amounts in the ovaries in women. The adrenal glands also contribute indirectly by producing dehydroepiandrosterone (DHEA), a hormone that the body can convert into testosterone and estrogen. Specifically in men, testosterone plays a vital role in:

• Development of male internal reproductive organs (fetal development)

• Development of male external reproductive organs (fetal development)

• Increase in height (puberty)

• Body and pubic hair growth (puberty)

• Enlargement of penis, testes, and prostate gland (puberty)

• Increased libido / sex drive (puberty & adulthood)

• Production of sperm (adulthood)

• Stimulation of red blood cell production (adulthood)

• Maintenance of bone strength (adulthood)

• Maintenance of muscle strength (adulthood)

• Support of overall well-being (adulthood)

Source: Cleveland Clinic, 2022

What are normal testosterone levels?

Testosterone circulates in the blood in two forms:

• Bounded testosterone

• Free testosterone (biologically active)

Total testosterone includes both fractions and is the value most commonly measured in clinical practice.

Below you can find the optimal testosterone levels: 

Note: Reference ranges can differ slightly depending on the lab. Only a healthcare professional can interpret results in the context of symptoms and overall health.

In men, testosterone levels rise during puberty, peak around age 18, and generally decline with age, particularly from the 40s onward. In women, testosterone levels are highest around age 20 and also decline naturally with age.

Source: Cleveland Clinic, 2022

What is low testosterone?

Testosterone deficiency occurs when the body does not produce enough testosterone. In men, this is often called male hypogonadism. In adult men, levels below 300 ng/dL are generally considered low. Reference ranges can vary by laboratory and testing method.

Source: Cleveland Clinic, 2026

Common causes of low testosterone in young men

Although testosterone naturally fluctuates throughout life, persistently low levels in young men are often linked to a variety of lifestyle, medical, genetic, or treatment-related factors:

1. Lifestyle and Environmental Causes

• Obesity / Excess body fat: Higher body fat is strongly linked to lower testosterone in men (Ma, H., et al., 2024). A study with young men aged 18-30 with moderate to severe obesity (BMI > 32.5), found more than 60% to have low testosterone (Shah, S. S., et al., 2024).

• Diet: Clinical trials show that low-fat diets can significantly reduce total and free testosterone in men, compared to diets with adequate healthy fats (Whittaker, J., & Wu, K., 2021).

• Sleep restriction: Just one week of <5 hours of sleep per night can reduce testosterone by 10-15% in young healthy men (Leproult, R., & Van Cauter, E., 2011).

• Endocrine-disrupting chemicals (EDCs): Exposure to EDCs (such as those found in plastics and pesticides), has been linked to lower testosterone levels, although human evidence is still mixed (Rodprasert, W., et al., 2021).
  

2. Medical & Health Conditions

• Pituitary or hypothalamic disorders: Problems in the brain’s hormone centers (the hypothalamus or pituitary gland) can block the signals that tell the testes to make testosterone, leading to central hypogonadism (Pivonello, R., et al., 2017).

• Chronic illnesses (e.g. cancer): Low testosterone is common in men with cancer and in cancer survivors, which can be caused both by the illness itself and by treatments such as chemotherapy, radiation, or surgery (Xu, P., et al., 2021). Certain chronic diseases such as HIV can also lead to lower testosterone levels.
  

• Hemochromatosis: Too much iron in the blood can cause the testicles to fail or the pituitary gland not to work as it should.

3. Genetic / Developmental Factors

• Klinefelter syndrome (XXY): It’s estimated that around 65-85% of men with Klinefelter syndrome have low testosterone (White, J. T., 2022). It is a genetic disorder in men caused by extra X chromosome(s). This can impair testosterone production and often leads to a deficiency of this hormone.

4. Medication & Treatment Side Effects

• Chemotherapy or radiation therapy: Can damage testosterone-producing cells. Low testosterone is common in testicular cancer survivors as a result (Walsh, J. S., et al., 2019).

• Substances (e.g. opioids): Research shows that 20-80% of men who use opioids long term develop low testosterone (Kafel, H., et al., 2025).
  

Source: Mayo Clinic, 2024

It is important to note that this list is not exhaustive and there may be many other potential causes of low testosterone levels. If low testosterone is suspected, medical advice should always be sought.

Signs and symptoms of low testosterone

Low testosterone may cause:

• Reduced sex drive

• Erectile dysfunction

• Loss of armpit and pubic hair

• Shrinking testicles

• Hot flashes

• Low or zero sperm count (azoospermia), leading to infertility

• Depressed mood

• Difficulties with concentration and memory

• Increased body fat

• Enlarged male breast tissue (gynecomastia)

• Decrease in muscle strength and mass

• Decrease in endurance

• Slowed growth in height, with arms and legs growing out of proportion (children)

• Reduced development of pubic hair (children)

• Reduced growth of penis and testicles (children)

• Less voice deepening (children)

• Lower-than-normal strength and endurance (children)

Source: Cleveland Clinic, 2022

When to see a doctor

If you are a young man experiencing multiple symptoms of low testosterone, it is important to consult a healthcare provider. Blood tests can measure testosterone levels, and further investigations can help identify underlying causes. For more convenience, you can also check your hormone levels at home with the Homed-IQ Testosterone Test, which provides accurate results from a simple finger-prick blood sample.

Tips for supporting healthy testosterone levels

Simple lifestyle choices can make a big difference in keeping testosterone levels healthy; here are some key tips:

1. Lose Excess Body Fat

Maintaining a healthy weight is one of the most effective ways to raise testosterone. Belly fat increases the enzyme aromatase, which converts testosterone into estrogen. Losing even 15-20 pounds (or lowering your BMI) can significantly improve testosterone levels. Even a one-point drop in BMI may correspond with a small rise in testosterone.

2. Do Resistance Training (Lift Weights)

Weightlifting is proven to boost testosterone and human growth hormone. You don’t need extreme training, lifting weights 2-3 times per week for 30-40 minutes can make a meaningful difference.

Focus on moderate- to high-intensity compound movements that work large muscle groups (e.g., squats, bench press, rows, deadlifts).

3. Add Aerobic Exercise

Combine strength training with cardio (such as brisk walking, running, or swimming). This supports testosterone production, improves cardiovascular health, and helps with fat loss.

4. Prioritize Deep, Quality Sleep

Most testosterone is produced during deep REM (rapid eye movement) sleep. Poor sleep, shift work, or circadian rhythm disruption can significantly lower levels.

Aim for 7-9 hours of consistent, high-quality sleep each night.

5. Eat a Nutrient-Dense, Balanced Diet

Avoid excess sugar, processed foods, food dyes, excessive caffeine, large amounts of dairy, red meat, and unhealthy fats.

Focus on:

• Fruits and multi-colored vegetables

• Fiber-rich whole foods

• Healthy fats (olive oil, fatty fish, nuts)

• Onions

• Oysters (rich in zinc)

• Fatty fish (omega-3s)

• Extra virgin olive oil

• Green tea

• Nuts (especially Brazil nuts — 1–2 per day for selenium)

• Ground flaxseed (about 1 tablespoon daily)

A well-rounded diet supports hormone balance and overall metabolic health.

6. Limit Alcohol and Avoid Tobacco

More than two alcoholic drinks per day can increase testosterone conversion to estrogen, impair sexual function, and reduce sperm count.

Tobacco use is linked to lower testosterone and reduced reproductive health. Quitting smoking may help restore healthier hormone levels.

7. Reduce Stress and Manage Cortisol

Chronic stress raises cortisol, a hormone that suppresses testosterone production and promotes fat storage.

Stress also affects mood, libido, and overall well-being. Practice stress-reduction techniques such as exercise, mindfulness, breathing exercises, and improving work-life balance.

Sources: University of Utah Health Care, 2025; Rakel, D., 2012; Harvard Health Publishing, 2024 

Measures to address low testosterone levels should be carefully evaluated and taken in consultation with medical professionals to ensure safe and effective treatment.

Frequently asked questions

How is testosterone deficiency diagnosed?

Testosterone in the blood is either bound to proteins or unbound (free). Most is bound to sex hormone-binding globulin (SHBG) or albumin, while free testosterone is more readily available for the body to use.

Testosterone levels can be measured with three main tests:

• Total testosterone: Measures both bound and free testosterone and is the most common test.
• Free testosterone: Measures only unbound testosterone and may help diagnose certain conditions.
• Bioavailable testosterone: Measures free testosterone plus testosterone loosely bound to proteins other than SHBG.

Together with the tests above, evaluating the symptoms a patient presents contributes to a comprehensive picture of testosterone levels and possible causes of deficiency.

Source: National Library of Medicine, 2025

What are the effects of high testosterone levels?

High testosterone can also cause noticeable changes, particularly in hair growth, menstruation, and fertility.Symptoms of high testosterone may include:

• Excess facial or body hair
• Hair loss resembling male-pattern baldness
• Voice changes
• Irregular or absent menstrual periods
• Infertility
• Acne

Source: National Library of Medicine, 2025

How can my diet contribute to balanced testosterone levels?

Protein is an essential part of a healthy diet. It not only is necessary for building muscle, but also helps you feel fuller longer. Omega-3 fatty acids, abundant in foods like fish and certain plant oils, support heart health and can indirectly positively influence testosterone levels. Foods rich in zinc, selenium, and magnesium, such as nuts, fish, and leafy green vegetables, may also help boost testosterone. While research suggests that vitamin D might play a significant role in testosterone levels, more studies are needed to confirm this relationship definitively. Foods like fatty fish, eggs, and vitamin D-fortified products are good sources of vitamin D (Pilz et al., 2011). It’s also important to minimize risk factors for low testosterone. Factors such as smoking, high alcohol consumption, and high cholesterol levels can affect testosterone levels (Cleveland Clinic, 2022).

What symptoms occur with excess testosterone?

Persistently elevated testosterone levels are rare and often associated with hormonal disorders or external hormone use (e.g., anabolic steroids).

Possible symptoms in men:

• Acne and oily skin

• Mood swings or increased irritability

• Hair loss

• Suppression of natural sperm production with external testosterone use

Possible symptoms in women:

• Excessive facial or body hair growth (hirsutism)

• Irregular menstrual cycles

• Acne

• Polycystic ovary syndrome (PCOS)
  

Source: Cleveland Clinic, 2025

Summary

Testosterone is the key male sex hormone, vital for sexual development, muscle and bone strength, mood, and fertility. In young men, persistently low levels may result from lifestyle factors, medical conditions, or genetics, leading to symptoms like fatigue, reduced libido, and infertility. Diagnosis through blood testing or an at-home testosterone test is important, while healthy habits such as good sleep, exercise, stress reduction, and balanced nutrition help support normal levels.