Testosterone deficiency (TD) explained

What is low testosterone?

As you get older, your body will go through some changes that you might expect. Perhaps you won’t be as lively as you once were or you might put on some weight. You may even notice a gradual loss of sex drive. But what if this isn’t just down to aging?

Testosterone deficiency (also called hypogonadism) is the medical term for having a very low testosterone level. It is caused either when the testicles do not function normally or when internal hormone production is out of control. TD can affect men of any age, however, there is a progressive decline in testosterone levels as men age.1

So why is testosterone so important? Testosterone not only enables a man to have an erection and experience sexual desire (libido),2 it is also helps to maintain your general health, positive mood2 and energy levels.4

Because of this, the effects of low testosterone span a whole range of symptoms such as lack of energy, depression, loss of libido, loss of facial and body hair and, potentially, increased risk of developing osteoporosis.5

What are the signs and symptoms of low testosterone?

The symptoms of low testosterone are wide-ranging, so it’s no wonder the problem often remains undetected for a long time or is put down to ‘just getting older’.


  • Tiredness
  • Lethargy
  • Lack of concentration
  • Depression
  • Problems with erections (erectile dysfunction)
  • Lack of sexual interest (libido)
  • Loss of muscle


  • Loss of body, facial and pubic hair
  • Increased breast tissue (gynaecomastia)
  • Small testicles
  • Increased BMI/ body fat (body mass index)

Long term risk

Testosterone deficiency is also associated with type 2 diabetes,8 a reduction in bone mineral density and cardiovascular disease.9

To find out if you should talk to your doctor and get your testosterone levels checked, take our online symptom checker

Check your symptoms

What are the causes of TD?

Men can develop low testosterone for a number of reasons, although sometimes the specific cause is unknown. Depending on the cause, symptoms may occur quickly or gradually, sometimes taking years to become noticeable.

Which men are most at risk of TD?

Men with erectile dysfunction

Over one third of men who have erectile dysfunction (ED) may also have low testosterone.10 If you have ED, it could be worth getting your testosterone levels checked. This is particularly important if your ED treatment doesn’t appear to be working very well.

Men with type 2 diabetes

Clinical studies have demonstrated a link between type 2 diabetes and low testosterone11 so, if you have type 2 diabetes and notice one or more of the other symptoms mentioned above, you could also have low testosterone. Diabetes can also be associated with ED – more than two thirds of diabetic men are affected by it.12

Men with cardiovascular problems

It is not yet clear if low testosterone causes or is a result of cardiovascular problems. However, it is highly likely that if you have, for example, coronary heart disease, atherosclerosis or high blood pressure, you could be at risk of having low testosterone13.

Men with obesity

There is a relationship between obesity and low testosterone levels although the exact reasons behind the link are still not fully understood. Obesity is thought to contribute to low testosterone and men with very low testosterone are also more likely to become obese which may increase the risk of cardiovascular disease.14 Obesity can also be associated with type 2 diabetes.15

Think you’ve got low testosterone?

Maybe you should do something about it

If you’re rarely in the mood for sex, often feel tired, have a low mood and perhaps have difficulty getting an erection, these aren’t just inevitable signs of getting older. You may be experiencing symptoms of low testosterone.

If you are concerned that you may have low testosterone, or you’re in any of the risk groups mentioned above, complete our symptom checker and talk to your doctor. With a simple blood test, it is possible to determine your testosterone level and establish whether or not you have low testosterone.

Check your symptoms

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