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What is Testosterone?

Testosterone is a hormone that is primarily produced in the testes of men and, to a lesser extent, in the ovaries of women and the adrenal glands of both sexes. It is the primary male sex hormone and plays an important role in the development of male reproductive tissues, such as the testes and prostate, as well as secondary sexual characteristics like increased muscle mass, bone density, and body hair. But testosterone isn’t just important for men; it is also a critical hormone for women, affecting their physical and emotional health as well.

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May 24, 2023

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Generally, normal testosterone levels in men range from 8.4 to 28.7 nmol/L(nanomoles per litre). However, levels in men and women can vary greatly based on time of day, age, diet, and exercise.

In men, testosterone levels are highest in the morning and lowest in the evening. This is because testosterone production is regulated by the body’s internal clock, which is known as the circadian rhythm. Testosterone levels can also be affected by a man’s age, with levels naturally declining as he gets older – sometimes called andropause or the ‘male menopause’.

Testosterone levels also vary greatly between individuals, and what is considered “normal” for one person may not be the same for another. Some men may have naturally higher or lower testosterone levels, and this can be influenced by genetics, lifestyle factors, and other health conditions.

In women, testosterone levels are much lower than in men, but they still play an important role in reproductive health. Normal testosterone levels in women range from 0.2 to 0.62 nmol/L. Women with higher levels of testosterone may experience symptoms such as acne, excess body hair, and irregular periods.

It’s important for both men and women to maintain healthy testosterone levels, as low levels can lead to a variety of health problems.

If you’re concerned about your testosterone levels, our range of testosterone tests can help. Our Advanced Testosterone Blood Test checks not only your testosterone levels, but 11 other biomarkers that affect testosterone production and provides a more comprehensive look at your hormone health, helping you to optimise your training and feel your best.


There are many factors that can impact testosterone levels in men. Age is a major factor; men’s testosterone levels naturally decline with age, starting around age 30. However, there are many other factors that can also impact testosterone levels, including:

  1. Obesity: Men who are overweight or obese are more likely to have lower testosterone levels[1].

  2. Poor Nutrition: A diet that is lacking in essential nutrients can also impact testosterone levels. For example, a diet that is high in processed foods and sugar can lead to insulin resistance, which can negatively affect testosterone[2].

  3. Lack of Exercise: Regular exercise is important for maintaining healthy testosterone levels. Men who lead sedentary lifestyles are more likely to have lower testosterone.

  4. Over Exercising: While regular exercise can increase testosterone production, overexercising can increase your cortisol levels and reduce the Leydig cells in your testicles, both of which can impact testosterone production[3].

  5. Medical Conditions: Certain medical conditions can also impact testosterone levels. For example, men with diabetes or liver disease may have lower testosterone levels.

  6. Medications: Certain medications can also impact testosterone levels. For example, opioids and steroids can lower testosterone levels.

  7. Substance Abuse: Substance abuse, including alcohol and drug abuse, can also negatively impact testosterone levels.

  8. Stress & Sleep: Chronic stress and lack of sleep can also lower testosterone levels.

Testosterone replacement therapy is available for men with low testosterone levels. However, this should only be done under the supervision of a healthcare provider, as testosterone replacement therapy can have potential risks and side effects.


While low testosterone levels can cause a variety of health problems, high testosterone levels – known as hyperandrogenism – can also be a concern. When testosterone levels are too high, it can lead to a range of symptoms and health problems.

One of the most common symptoms of high testosterone levels in men is excessive facial or body hair.

Another symptom of high testosterone levels in men is acne. Testosterone stimulates the production of sebum, an oily substance that can clog pores and lead to breakouts. This can be particularly problematic for men who are already prone to acne.

Men with high testosterone levels may also experience an increased sex drive. Testosterone is a key factor in male libido, and high levels of the hormone can lead to a heightened desire for sexual activity. While this may be a positive for some, it can also lead to relationship problems and sexual dysfunction if not managed properly.

In addition to these symptoms, men with high testosterone levels may also experience balding, irritability, and aggression. This is because testosterone can have an impact on mood and behaviour, leading to increased feelings of anger and hostility.


Low testosterone in men, also known as hypogonadism, can lead to a range of health problems, including decreased energy levels, reduced muscle mass, and increased body fat. Symptoms of low testosterone can also include decreased libido, erectile dysfunction, and depression.

As men age, their testosterone levels naturally decrease, but in some cases, the decrease can be more significant and can lead to hypogonadism.

Treatment for low testosterone can include testosterone replacement therapy (TRT), which can be administered through injections, patches, gels, or pellets. Lifestyle changes, such as weight loss and exercise, can also help to increase testosterone levels naturally.

Low testosterone levels in men can lead to a range of health problems and should be taken seriously. If you suspect that you may have low testosterone levels, speak with your GP or order a testosterone blood test online.


Although women have much lower levels of testosterone than men, it’s still important for women’s reproductive and overall health.

Testosterone levels in women can have a significant impact on their physical health, emotional wellbeing, and sexual function. Women with low testosterone levels may experience fatigue, decreased sex drive, and difficulty building muscle mass. This can lead to feelings of frustration and decreased confidence.

On the other hand, high testosterone levels in women can lead to a condition called hirsutism, which is characterised by excess hair growth on the face, chest, and back. Women with high testosterone levels may also experience acne, mood swings, and an increased sex drive.

Testosterone levels in women naturally fluctuate throughout their lives. During puberty, girls experience an increase in testosterone, which contributes to the development of pubic and underarm hair, as well as an increase in sex drive. Testosterone levels also decrease as women age, which can contribute to a decline in muscle mass and bone density.

Women who engage in regular strength training exercises may experience an increase in testosterone levels, which can improve muscle mass and overall physical health.


Testosterone is important for both men and women when it comes to exercise.

One of the key roles of testosterone is to promote the growth and repair of muscle tissue. When you exercise, you create small tears in your muscle fibres. Testosterone helps to repair these tears, leading to an increase in muscle mass and strength over time. This is why testosterone is often referred to as an anabolic hormone.

It also plays a role in metabolism, helping to regulate the way your body processes food and stores fat. When testosterone levels are high, your body is more efficient at burning fat and building lean muscle. This can lead to improved cardiovascular health and athletic performance, as well as a more toned and defined physique.

Overall, while testosterone is an important hormone for exercise and athletic performance, it’s important to remember that it’s just one piece of the puzzle when it comes to achieving your fitness goals. A balanced diet, regular exercise, and plenty of rest and recovery are all crucial for building a strong, healthy body.

Medically Reviewed

Dr Thom Phillips

This article has been reviewed by our medical expert

Our expert Dr Thom Phillips works in NHS general practice and has a decade of experience working in both male and female elite sport. He has a background in exercise physiology and has published research into fatigue biomarkers.