Low testosterone can cause a cluster of symptoms in men — most tellingly a drop in sex drive, fewer morning erections and erectile difficulties, alongside less specific signs like fatigue and low mood. But a single low blood result on its own isn't a diagnosis, and many symptoms blamed on "low T" have other causes. This guide explains which signs actually point to low testosterone, what causes it, and how testing works in the UK.
Key takeaways
- The symptoms most specifically linked to low testosterone are sexual: reduced desire, fewer morning erections and erectile dysfunction (Wu et al., European Male Ageing Study, 2010).
- A low number is not the same as the condition. In one large European study, 17% of men aged 40–79 had a low reading, but only 2.1% had the full condition (low testosterone plus symptoms) (EMAS, 2010).
- A blood test should be taken in the morning (before 11am), ideally after fasting, and repeated to confirm (BSSM 2023).
- Being overweight or having type 2 diabetes roughly doubles the odds of low testosterone, and losing weight can raise levels (BSSM 2023; Corona et al., 2013).
- Never buy testosterone online. It's a prescription-only, controlled medicine, and self-treating is risky and can harm fertility (NHS).
The symptoms, ranked by how specific they are
Not all "low T" symptoms are equally meaningful. The landmark European Male Ageing Study (EMAS) tested 3,369 men aged 40–79 across eight European centres, including Manchester, against 32 possible symptoms. Only three clustered reliably with low testosterone, and all three were sexual (Wu et al., 2010).
| How suggestive | Symptoms |
|---|---|
| Most specific | Reduced sexual desire, fewer morning erections, erectile dysfunction |
| Sometimes linked | Low energy and reduced physical strength, more belly fat, lower muscle and bone density; occasionally hot flushes |
| Non-specific | Fatigue, poor sleep, low mood, poor concentration |
That last row matters. Psychological symptoms like low mood had little or no direct link to testosterone level in EMAS (Wu et al., 2010). The Society for Endocrinology also notes that mood, sleep and thinking symptoms are much less likely to improve with treatment than the sexual ones (SfE, 2022).
How strongly symptoms point to low testosterone
A low result is not a diagnosis
This is the single most important point. Low testosterone as a condition means a genuinely low level together with symptoms — not a number in isolation.
In EMAS, among men aged 40–79 (Wu et al., 2010):
- 17.0% had a total testosterone below 11 nmol/L
- 4.1% were below 8 nmol/L
- but only 2.1% had the actual condition — low testosterone plus the sexual symptoms
How common is low testosterone, really?
That's why guidelines insist on interpreting a result alongside symptoms, and on confirming it.
What causes low testosterone
Testosterone does decline slowly with age — the NHS puts it at about 1% a year from around 30 to 40, which by itself is unlikely to cause problems (NHS). More often, a genuinely low level is linked to another condition or a medication.
Common contributors (BSSM 2023):
- Being overweight (roughly doubles the odds) and type 2 diabetes (also roughly doubles it)
- kidney disease, COPD, obstructive sleep apnoea, HIV, anaemia and osteoporosis
- some medicines, including opioids, oral steroids, antipsychotics and anticonvulsants
In younger men, causes include anabolic steroid use (which shuts down the body's own production and can affect fertility for months to years), opioids, and less commonly a pituitary problem or Klinefelter syndrome — a genetic condition affecting about 1 in 660 males, of whom around a quarter are never diagnosed (SfE, 2022; NHS).
"Male menopause": is it real?
You'll see the term "male menopause" (or andropause), but the NHS calls it unhelpful and misleading, because it implies a sudden mid-life drop in testosterone that doesn't reflect what actually happens. The NHS points out that symptoms often blamed on it — low mood, poor sleep, low energy — frequently come from stress, depression, anxiety, poor sleep, diet, too little exercise, alcohol or smoking. A genuine, specific hormone deficiency (late-onset hypogonadism) does exist but is uncommon, and is more likely in men with obesity or type 2 diabetes (NHS).
It genuinely becomes more common with age. In EMAS, the full condition affected 0.1% of men in their 40s, rising to 5.1% of men in their 70s (Wu et al., 2010).
How testing works, and how to prepare
Testosterone varies through the day and is affected by food and illness, so how and when you're tested matters. UK guidance advises (BSSM 2023; SfE, 2022):
- have the blood taken in the morning, before 11am (ideally around 8–10am)
- fast beforehand if you can — a sugary drink can lower testosterone by around 25%, and non-fasting results can read up to 30% lower
- don't test during an acute illness
- expect a second morning test to confirm a low result
- tell the clinician about every medicine, supplement and any recreational drug use
What gets measured. Total testosterone is the first test. If it's borderline, a clinician may add SHBG and calculate free testosterone, and if it's low they'll usually check LH and FSH to work out where the problem lies (BSSM 2023).
A word on lab ranges. UK labs are inconsistent — the lower limit of "normal" can range from about 4.9 to 11 nmol/L depending on the lab. Because of that, treatment decisions should use published clinical action levels, not just whether you fall inside a lab's printed range (Ann Clin Biochem / SfE joint statement, 2023). Current BSSM guidance treats a total testosterone below 12 nmol/L, in a man with symptoms and two morning samples, as usually needing attention — a change from the older 2017 threshold of 8 nmol/L (BSSM 2023).
Our guide to getting a testosterone test in the UK covers this in more detail. Not sure whether your symptoms are worth raising? Run through our free testosterone symptom checker first.
Low testosterone in women
Women produce testosterone too, in the ovaries and adrenal glands, at much lower concentrations. Levels fall gradually with age and sharply after both ovaries are removed. The symptoms attributed to it — low desire, fatigue, low mood, reduced muscle strength — overlap almost completely with perimenopause, thyroid disease and iron deficiency, and there is no agreed reference range for women in the way there is for men.
Because the guidance, the testing and the thresholds are all different, we cover it separately: see testosterone in women for what NICE actually recommends and why it is an off-label use in the UK.
Can low testosterone cause anxiety?
Low mood, irritability and reduced stress tolerance are recognised features of testosterone deficiency, and anxiety is frequently described alongside them. But the relationship runs in both directions, which is what makes it difficult to untangle.
Anxiety, chronic stress and poor sleep all suppress testosterone. So a man with anxiety and a low reading may have anxiety causing the low result rather than the other way round — and treating the hormone while leaving the cause untouched would be the wrong order.
It is also worth saying plainly that persistent anxiety deserves assessment on its own terms, not only as a hormone symptom. If anxiety is the dominant problem, that is the thing to get help with first, whatever the testosterone result turns out to be.
Can lifestyle help?
For weight-related low testosterone, often yes. A meta-analysis of 24 trials found a low-calorie diet raised total testosterone by an average of 2.87 nmol/L, and how much weight was lost was the strongest predictor of the rise (Corona et al., 2013). Sleep matters too: in a small study of healthy young men, a week of under five hours' sleep a night cut daytime testosterone by 10–15% (UChicago Medicine / Leproult & Van Cauter, 2011).
The honest caveat: lifestyle changes alone are unlikely to relieve severe symptoms if levels are genuinely very low, and the weight loss usually needs to be substantial (BSSM 2023). If weight is part of the picture, our guide to a healthy BMI and waist-to-height ratio explains how to gauge it.
About treatment
Whether treatment is right depends on your symptoms, your blood results and your overall health, and it's a decision to make with a clinician — not something to buy online. UK expert guidelines don't fully agree on the details (for example, on when to trial treatment or how to monitor the prostate), which is another reason it needs a proper individual assessment (BSSM 2023; SfE, 2022). If you're planning to have children, that should always be discussed first, because treatment can reduce fertility.
Renvo can help. Our men's health service assesses your symptoms with clinicians who specialise in this area, arranges the right blood tests, and talks you through what the results mean and your options. Book a consultation
When to see a GP
See a GP promptly if a drop in libido or erection problems comes alongside (SfE, 2022; yourhormones.info):
- headaches or changes in vision (which can point to a pituitary problem)
- breast growth or tenderness, small testicles, or infertility
- unexplained anaemia, or a fracture from a minor injury
And a safety point worth repeating: don't buy testosterone or anabolic steroids online or from unregulated sources. They're prescription-only, controlled medicines; self-treating can cause serious harm and affect fertility (NHS). If low mood is part of the picture and you ever feel unable to keep yourself safe, call 999, NHS 111, or Samaritans free on 116 123 (NHS).
Honest FAQs
What are the first signs of low testosterone?
The most specific early signs are sexual: reduced sex drive, fewer morning erections and erectile difficulties. Fatigue and low mood can occur too, but are less specific and have many other causes (Wu et al., 2010).
Can I get a testosterone test on the NHS?
Yes — a GP can arrange a blood test if your symptoms suggest low testosterone, and may refer you to a hormone specialist if it's confirmed (NHS).
What time of day should a testosterone test be done, and do I need to fast?
It should be taken in the morning, before 11am (ideally 8–10am), and ideally after fasting, because levels are higher in the morning and food lowers them. A low result should be confirmed with a second morning test (BSSM 2023).
Can low testosterone be reversed naturally?
For low testosterone driven by excess weight, losing weight can raise levels, and better sleep helps (Corona et al., 2013). But lifestyle alone may not be enough when levels are very low, so it's worth a proper assessment (BSSM 2023).
Is the "male menopause" real?
A sudden mid-life "male menopause" isn't an accurate picture — the NHS calls the term misleading. A genuine, specific testosterone deficiency does exist, but it's uncommon and needs proper diagnosis (NHS).
This article is general information, not medical advice. Always speak to a qualified clinician about your own symptoms and any treatment.
