What it is, what your weight has to do with it, and when to get checked.
Reviewer: Dr Ibrahim (Envigore Medical Advisor)
Testosterone quietly runs more of a man’s day-to-day than most realise, and when it drops the signs are easy to file under simply getting older. Here is a straight look at what low testosterone is, and the questions men most often ask. For many men, one lever does more than any supplement ever will.
What testosterone does
Testosterone is the main sex hormone in males, although it is also found in females. It drives libido and penile erections, helps build muscle and bone, supports mood, energy and concentration, and keeps sperm production going. When it falls too low, any of those can suffer.
The signs of low testosterone
Low testosterone, sometimes called low T, is easy to miss, because the signs creep in and look like ordinary life. The most telling is a real drop in sex drive. Others include:
- Weaker or fewer erections, including fewer morning erections.
- Persistent fatigue and low motivation, despite enough sleep.
- Losing muscle or strength, or getting less from the gym.
- Gaining fat, especially around the middle.
- Low mood, irritability or poor concentration.
- In older men, thinning bones.
Any of these can have other causes, which is exactly the point. You cannot diagnose low testosterone by how you feel.
Is it just ageing?
Partly. Testosterone falls slowly with age, by roughly 1 percent a year from around 30 to 40, and that gentle decline is normal. What is not simply age is a level low enough to cause symptoms, especially in a younger man, or a sharper drop after illness, stress or weight gain. Feeling flat in your forties is common. It is not something to shrug off without checking.
The weight connection
Here is the part many men are not told. Carrying excess weight, particularly around the middle, actively lowers testosterone. Fat tissue contains an enzyme called aromatase that converts testosterone into oestrogen, so the more fat you carry, the more testosterone you lose. It becomes a loop. Low testosterone makes it easier to gain fat, and more fat lowers testosterone further.
The encouraging news is that the loop runs both ways. A systematic review of trials found that losing weight raises testosterone, whether through diet, exercise or medical weight loss, by cutting that aromatase activity and improving insulin sensitivity and inflammation. For many men carrying extra weight, addressing the weight is the most effective thing they can do for their testosterone, and it treats the cause rather than masking it.
Testosterone and erections
Low testosterone and erectile dysfunction are linked, but they are not the same. Testosterone drives libido, your sex drive, and low levels interfere with those signals. But it is the blood vessels and the nervous system that directly control an erection. So very low testosterone can contribute to ED without being the direct cause. Plenty of ED has nothing to do with testosterone at all, and everything to do with blood vessels. That is why a good clinician looks at the whole picture rather than testosterone alone. If ED is your main concern, our erectile dysfunction service is the place to start, and our article on weight and erectile dysfunction goes deeper.
Should I get tested, and how?
If several signs ring true, the only way to know is a blood test, not a guess and not a supplement. Testosterone is measured from a morning sample, when it is highest. A diagnosis needs two low readings on separate mornings, because up to a third of first low results come back normal on retest. Your clinician may add other hormone tests to find the cause. In the UK, levels are reported in nmol per litre, and a clinician reads them alongside your symptoms rather than a single number.
What about testosterone replacement therapy?
Testosterone replacement therapy can help men with clearly low levels and symptoms, improving libido, energy, mood, muscle and bone. It is not a lifestyle booster, though, and it carries real considerations. It can reduce sperm production and fertility, it is not suitable for men with prostate or breast cancer, and its labelling now carries cautions about heart and blood-vessel risk. It is started only after confirmed low readings, with ongoing monitoring, and it is a decision for an endocrinologist or equally qualified clinician to manage. If your testosterone is low because of your weight, treating the weight first is often the better opening move.
Natural ways to support your testosterone
Before anyone reaches for a pill, the basics move the needle, and they cost nothing:
- Lose excess weight. The single biggest lever for most men.
- Strength training. Resistance work supports testosterone and muscle together.
- Sleep. Poor sleep lowers testosterone quickly, since much of it is made overnight.
- Go easy on alcohol, and do not smoke.
- Manage stress. Chronic stress raises cortisol, which works against testosterone.
Ignore the testosterone booster supplements. The evidence is that most do little or nothing, and some are not what they claim.
When to see someone
If low sex drive, persistent fatigue, mood changes or erection problems have become your normal, do not file them under getting older. Get checked. It may be your testosterone, it may be your weight, or it may be something else worth catching early, such as your heart or your blood sugar. Erectile dysfunction in particular has several possible causes, including those named above and a range of cardiovascular conditions.
Where we can help
At Envigore, the strongest lever we can offer for many men’s testosterone is also our core work: helping you lose excess weight safely, which raises testosterone at the source. We can also help with erectile dysfunction directly. For testosterone testing and replacement therapy itself, that is a matter for an endocrinologist or equally qualified clinician, usually reached through your GP, and we are glad to point you there. You can start a consultation at www.envigore.com.
Frequently asked questions
These questions reflect the guidance above and are reviewed by our clinical team before publication.
Some decline is normal, around 1 percent a year from your thirties. But a level low enough to cause symptoms is not simply age, especially if you are younger or the change was sudden. Symptoms that affect your life are worth checking, not shrugging off.
Yes. Excess fat lowers testosterone by converting it into oestrogen, and studies show that losing weight, through diet, exercise or medical weight loss, reverses much of that. For many men carrying extra weight it is the most effective and natural way to raise testostero
You need a blood test. The symptoms overlap with many other things, so they cannot confirm it. Testing uses a morning sample, and a diagnosis needs two low readings on separate days, because first results are often normal on retest.
Mostly no. The evidence is that most over-the-counter boosters do little or nothing, and some are not what they claim. Your money and effort go further on weight, sleep, strength training and cutting back on alcohol, which do help.
No, though they can be linked. Testosterone drives libido, but it is the blood vessels and the nervous system that directly control an erection. Very low testosterone can contribute to ED, though much ED has nothing to do with testosterone at all. That is why the whole picture matters, and why ED is worth assessing in its own right.
+ Sources
- Corona G, et al. Body weight loss reverts obesity-associated hypogonadotropic hypogonadism: a systematic review and meta-analysis. European Journal of Endocrinology, 2013.
- Impact of Weight Loss on Testosterone Levels: a review of BMI and testosterone (aromatase mechanism). PMC, 2025.
- British Society for Sexual Medicine (BSSM). Guidelines on the management of adult testosterone deficiency.
- Urology Care Foundation / Cleveland Clinic. Low testosterone: symptoms, diagnosis and treatment (patient overview).
- US FDA. Class-wide labelling changes for testosterone products (cardiovascular caution), 2025.
About Your Clinical Team
This content was medically reviewed and approved by Danny Gian Hou Chu, a HCPC-Registered Advance Paramedic Prescriber (PA38670), who oversees all prescribing decisions at Envigore.
All prescriptions are dispensed by Right Medicine Pharmacy, a GPhC-Registered Pharmacy (No. 9012382).
Nutritional guidance and lifestyle support is provided by Veronica Giudice, a HCPC-Registered Dietitian (DT26570) and British Dietetic Association member.
Last medically reviewed: July 2026