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Testosterone is a hormone that causes male characteristics. For men, it helps to regulate sex drive and has a role in controlling bone mass, fat distribution, muscle mass, strength and the production of red blood cells and sperm. Testosterone is produced in the testicles of men and, in much smaller amounts, in the ovaries of women.

Testosterone levels in men naturally decline after the age of 30, although lower than normal levels can occur at any age and can cause low libido, erectile dysfunction, difficulty in gaining and maintaining muscle mass and lack of energy. Although women have much lower amounts of testosterone than men, it is important for much the same reasons, playing a role in libido, the distribution of muscle and fat and the formation of red blood cells.

All laboratories will slightly differ in the reference ranges they apply because they are based on the population they are testing. The normal range is set so that 95% of men will fall into it. For greater consistency, we use the guidance from the British Society for Sexual Medicine (BSSM) which advises that low testosterone can be diagnosed when testosterone is consistently below 8 nmol/L and that levels below 12 nmol/L could also be considered low, especially in men who also report symptoms of low testosterone, or who have low levels of free testosterone.

What might a low result mean?

For men, it is much more common to have borderline or low testosterone than to have naturally elevated testosterone. There are many factors which can contribute to low testosterone, including increasing age, obesity, chronic illness, alcoholism and stress (including over-exercising), as well as certain genetic conditions such as Klinefelter syndrome. A common reason for low testosterone is steroid use, where high circulating testosterone in the body causes the natural production of testosterone by the testes to shut down.

What might a high result mean?

Elevated testosterone is not commonly seen in men unless you are taking supplements aimed at raising testosterone levels e.g. testosterone replacement therapy or steroids. It is important to keep testosterone to within the normal range for men so that you don't experience the side effects of elevated testosterone. Having high testosterone can impact the levels of other hormones, such as oestradiol, and can switch off the body's own testosterone production. In rare circumstances, high testosterone may be due to a testosterone-producing tumour.

In women, raised testosterone can indicate polycystic ovary syndrome (PCOS). If you are experiencing irregular periods or no periods at all, excessive hair growth on the body and thinning hair on the head, weight gain and acne we recommend you speak with your doctor.

How might I improve my result?

If you want to increase your testosterone there are some lifestyle changes that you can make that may boost levels. Aim to get between 7 and 9 hours sleep per night and avoid alcohol. Keep your weight in a healthy range and eat a diet rich in healthy fats, protein and carbohydrates (avoiding refined carbs and sugar). Strength exercise can boost testosterone as can HIIT (high intensity interval training). Vitamin D, magnesium and zinc have been shown to help testosterone levels, so if you don't get enough from your diet (and sunshine in the case of vitamin D) then consider supplements. Finally, try to minimise stress (including exercise induced stress from over-reaching and over-training) and make enough time for rest and relaxation.