Struggling with low energy, stress, or performance issues? This test measures testosterone and cortisol, two key hormones that influence strength, recovery, metabolism, and stress response. It’s ideal for those wanting to assess hormonal balance, fitness performance, or the impact of stress on overall well-being.
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What's in the test?
Adrenal hormones
Cortisol
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Cortisol is a stress hormone produced by the adrenal glands. It is vital to survival given its role in functions such as immunity, regulating blood pressure and releasing insulin for blood sugar maintenance.
Hormones
Testosterone
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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 the reference range, 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.
Testosterone : cortisol
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The Testosterone/Cortisol (T:C) ratio is a marker which shows promise in assessing whether athletes are recovering well after intense training. Testosterone is an anabolic hormone which helps to build muscle, produce red blood cells and increase aerobic metabolism in muscles. Cortisol is a catabolic hormone working antagonistically with testosterone, inhibiting protein synthesis and blocking anabolic signalling. The T:C ratio is more sensitive to the stresses of training than either measure alone. Over time it can be trended to see how well you are recovering.
How to prepare for your test
Prepare for your Testosterone and Cortisol Blood Test by following these instructions. Take your sample between 6am and 10am. If you have an unusual sleep pattern, your cortisol results may be unreliable. If you must test, do so within 2 hours of waking and inform us in the supporting information. Corticosteroid medication can affect this test, ask your doctor whether to stop before testing. Avoid taking a finger-prick sample from a finger used to apply hormone gels/pessaries/patches in the past 4 weeks. Use gloves to apply these. Do not take biotin supplements for two days before this test, discuss this with your doctor if it is prescribed. Hormonal contraception can affect the results of this test. Taking a break from this and waiting for your periods to restart before your blood test will give more accurate results.
Test limitations
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FAQs
What does testosterone do?
Testosterone is a hormone that causes male characteristics. For men, it regulates the sex drive and controls bone mass, fat distribution, muscle mass, strength, and the production of red blood cells and sperm. Heavy alcohol use, liver disease, and using steroids can cause a decrease in testosterone levels. Women taking oestrogen therapy, however, may have increased testosterone levels.
What does cortisol do?
Cortisol is a steroid hormone, produced by the adrenal gland. It's vital for survival as it's involved in various functions such as immunity, regulating blood pressure, and releasing insulin for blood sugar maintenance. Cortisol is known as the stress hormone because it's secreted at higher levels during the body's fight or flight response to stress and is responsible for several stress-related changes in the body.
What is the testosterone to cortisol (T:C) ratio?
The testosterone to cortisol (T:C) ratio is a marker that shows promise in assessing whether athletes are recovering well after intense training, and raised cortisol can inhibit the production of testosterone. T:C ratio is more sensitive to the stresses of training than either measure alone. Over time, you can trend your results to see how well you are recovering.
Why have the male reference ranges for testosterone changed?
The reference range for testosterone has been adjusted to have a lower limit of 12 nmol/L to reflect guidance from the British Society for Sexual Medicine (BSSM) 2022.
Our medical advice regarding testosterone levels remains the same and we advise that if your total testosterone level is between the range of 8-12 nmol/L and you have symptoms of low testosterone you may be considered eligible for testosterone replacement therapy. If your testosterone level falls within this range but you have no symptoms this is considered satisfactory and no further action is required.