Signs that you might have low testosterone

Published on 31 December 2018

Testing and diagnosis


The issue of low testosterone is increasingly highlighted in the media and health magazines, and is the topic of medical controversy about how to diagnose it, and which men should be treated. Alongside my private clinical work at Imperial Reproductive Endocrinology, I lead a research team at Imperial College London studying these two important issues, and receive new referrals each week to advise men about whether they have low testosterone. I don’t think it is possible to tell men what I think without first explaining the background to testosterone and what makes it low. Without this critical information, men may not be fully able the make the right decision with their doctor.

What is testosterone and what is its purpose?

Testosterone is the main sex hormone in men. It is made in the Leydig cells of the testes, and falls within the steroid family of hormones. The major function of testosterone is to support multiple aspects of normal reproductive function, including:

  • Male pattern muscle development
  • Male pattern hair growth
  • Libido (interest in sex)
  • Having erections

Testosterone also affects your metabolism, is needed for the prostate to work, and stimulates your bone marrow to make new red blood cells (erythropoiesis). Levels of testosterone production are highest in the morning when you wake up, and are lowest at night (diurnal rhythm). Levels of testosterone also drop by 20% when you have a meal. This all means that levels of testosterone are ideally measured in the morning when you have missed breakfast, to give the highest possibly testosterone reading. 

What defines low testosterone?

There is a lot of controversy about how low testosterone needs to be before it should be treated. Based on the published scientific evidence to date, testosterone levels above 12nmol/L (350ng/dL) are likely to be normal, and levels below 8nmol/L (230ng/dL) are probably too low. However, levels between 8-12nmol/L are borderline where looking at calculated free testosterone levels or haemoglobin may be helpful to decide what to do.

What signs might I have if I am suffering from low testosterone?

Sexual symptoms are the only reliable signs of low testosterone. This might include a loss of erections when you wake up, reduced interest in sex (libido) or reduced ability to have an erection. Studies have shown that other symptoms such as tiredness and low mood are usually not caused by having a low testosterone.

How can I get tested for low testosterone?

It is important to get an accurate measurement of testosterone from your blood. The test for testosterone should be done in the morning. The blood test should ideally be done when you have missed breakfast, since we know that eating alters testosterone levels temporarily. The method of measuring testosterone (assay) can vary between hospitals, so it is important that the method is regularly tested for accuracy against other hospital (validation). 

Some men have ‘borderline’ low testosterone; this means there is uncertainty whether they have a problem. We specialise in treating this group of men to provide a definitive answer about whether a man has a low testosterone. This involves repeated measurements, calculation of free testosterone, measurement of other hormones and looking for evidence that other parts of the body lack testosterone. 

Home testing kits for testosterone are not recommended by guidelines, since they are not proven to give accurate information. We would recommend testing in a hospital that participates in a national quality control scheme. We use state-of-the-art testosterone measurements at Imperial College Healthcare, which are subject to the most rigorous standards.

What causes low testosterone?

Low testosterone can be caused by a few types of disorder:

  • The testes do not make enough testosterone (primary hypogonadism)
  • The pituitary gland does not stimulate the testes enough to make testosterone (hypogonadotrophic hypogonadism)
  • Chronic illness such as diabetes and some medications
  • Poor physical health such as lack of physical activity and obesity
  • Ageing related low testosterone (late onset hypogonadism)
  • A small number of men may have low testosterone which is caused by uncommon genetic problems such as Klinefelter syndrome.

Ageing related low testosterone (late onset hypogonadism - LOH)

Levels of testosterone naturally drop by 1% per year in men beyond the age of 40. This means that it is normal for older men to have lower testosterone levels than younger men. The term andropause has been used to describe this phenomenon (as an equivalent to menopause in women), but I do not think this term is helpful, since we know that 98% of older men will not experience any symptoms or harm from the natural decline of testosterone associated with ageing. 

The European Male Ageing Study (EMAS) was conducted in 3000 men aged over the age of 40 across Europe. They showed that sexual symptoms such as low libido and problems with erections are associated with having low testosterone levels. However, other symptoms such as physical and mental tiredness, were not associated with testosterone levels. Put another way, it is easy to think that many symptoms associated with ageing could be blamed on low testosterone. However, only sexual symptoms are associated with low testosterone. 

Some men are keen to take testosterone even if they do not have low testosterone levels. This is risky and I caution against it, due to the risks of blood clots (thrombosis), heart disease and stroke. Similarly, if you are and older man, or have pre-existing heart problems or stroke, then it is important to go through the risks versus benefits of treatment with your doctor. 

What does a treatment plan look like?

Exercise and weight loss is a great first step to try improving testosterone levels. This particularly applies to men with type 2 diabetes and obesity, where lifestyle measures can even normalise testosterone levels.

Testosterone replacement may be either be applied daily to the skin as a cream, or taken as an injection every few months. It should typically take days to feel an improvement in symptoms. We have a lot of experience helping patients get on the right formulation of testosterone and the correct dose. Once established on testosterone therapy, you should have an annual review to check levels of haemotocrit (red blood cells). Testosterone naturally causes prostate gland growth, which has made specialists speculate if testosterone increases prostate cancer risk. Clinical guidelines recommend that testosterone does not cause prostate cancer, but we should avoid giving it to men with active prostate cancer. For these reason, it has been recommended that men over the age of 40 years may require a prostate check. 

As one of the UK’s major specialist centres for  testosterone replacement, we see about one hundred men annually. The aim of management is to create a tailored treatment plan for our patients to give effective symptom relief in the most convenient and safest way.