What every man over 40 needs to know about testosterone

As men move into their 40s and beyond, they often start to feel changes they can’t quite put their finger on – lower energy, reduced drive, stubborn belly fat, and even a shift in mood or motivation. It’s easy to chalk it up to a demanding lifestyle or getting older, but there’s often a biological factor at play that most men overlook: testosterone. 

This key hormone does far more than fuel libido and gym gains. It plays a central role in energy levels, mental focus, mood, muscle mass, and metabolic health. And from around age 30, testosterone levels in men begin to decline naturally – on average by 1-2% per year. 

So, if you're a man over 40 and you've been wondering why you don't quite feel like yourself lately, here's what you need to know about your hormones – and what you can do about it. 

What is testosterone and why does it matter?  

Testosterone is the primary androgen hormone in males, produced mainly by the testes and, to a lesser degree, the adrenal glands. It’s responsible for male sexual development, reproductive function, and a host of vital body processes, including: 

• Building and maintaining lean muscle mass 

• Supporting bone density 

• Regulating mood and mental clarity 

• Promoting a healthy sex drive and erectile function 

• Aiding in fat metabolism 

• Supporting red blood cell production 

Put simply, testosterone affects nearly every system in a man's body – which is why low levels can create such a wide range of symptoms. 

Common signs of low testosterone in men over 40 

Many men assume declining testosterone only causes issues in the bedroom, but the reality is far broader. Here are some of the most common (and often overlooked) signs of testosterone deficiency: 

• Persistent fatigue, even after a good night’s sleep 

• Loss of motivation or drive (in work, fitness, or life) 

• Reduced muscle mass and strength 

• Increase in body fat, especially around the middle 

• Decreased libido or sexual performance issues 

• Mood swings, irritability, or mild depression 

• Poor concentration or ‘brain fog’ 

• Difficulty sleeping or staying asleep 

These symptoms can come on gradually, which makes them easy to dismiss or misattribute to stress, parenting, or age. But for many men, low testosterone is a missing piece of the health puzzle. 

What causes testosterone to decline?  

While age is a natural factor, it's not the only reason why testosterone dips. Lifestyle and health status play a significant role too. Some key contributors include: 

• Chronic stress: high levels of the stress hormone cortisol can blunt testosterone production. Cortisol and testosterone have an inverse relationship – when one goes up, the other tends to go down. 

• Poor nutrition: low intake of essential nutrients such as zinc, magnesium, vitamin D, and healthy fats can impair the body’s ability to produce testosterone efficiently. 

• Lack of quality sleep: testosterone production peaks during deep sleep. Interrupted or insufficient sleep reduces your body’s ability to replenish hormone levels. 

• Excess alcohol or refined carbs: these can contribute to insulin resistance, an overworked liver, and body fat accumulation – all of which negatively impact testosterone.

• Increased aromatase activity: obesity, insulin resistance, and excess alcohol can increase aromatase – an enzyme that converts testosterone into oestrogen. Increased oestrogen levels in men can also worsen symptoms like low libido, fatigue and fat gain – creating a vicious cycle. 

• Sedentary lifestyle: physical activity, especially strength training, stimulates testosterone production. A sedentary lifestyle has the opposite effect. 

• Poor gut health: emerging research links gut health to hormone regulation, including testosterone. An imbalanced gut microbiome may indirectly reduce androgen levels through inflammation and impaired nutrient absorption. 

• Environmental toxins: we’re now surrounded by chemicals that can interfere with how hormones talk to each other. One well-studied culprit is BPA (bisphenol A) found in many plastics and food packaging. BPA can bind to androgen receptors, potentially blocking testosterone’s effects in the cells. Other hormone-disrupting chemicals, including phthalates and pesticides, may also lower testosterone. 

• Elevated sex hormone-binding globulin (SHBG): SHBG binds to testosterone in the blood making it inactive. When SHBG is too high, even ‘normal’ total testosterone levels can result in low free testosterone. SHBG can rise due to certain medications, liver dysfunction or a thyroid imbalance. 

• Thyroid imbalance: thyroid hormones help regulate SHBG production. When the thyroid is inactive (think hypothyroidism), SHBG levels may increase, reducing available free testosterone. A sluggish thyroid can also affect energy, mood and metabolism. 

Should you get your hormones tested?  

If you’re experiencing several of the symptoms above, it may be worth considering a male hormone test. These can identify imbalances not just in testosterone, but also in related markers like DHEA, oestradiol, cortisol, and SHBG. 

Testing options include: 

• Blood tests: typically used in standard NHS and private GP testing.

• Saliva or urine testing: these can provide insight into hormone fluctuations over time and are often used in functional medicine. 

An important note: total testosterone alone doesn’t always give the full picture. You’ll want to look at free testosterone (the active form) and how it interacts with other hormones and lifestyle factors. 

5 natural ways to support healthy testosterone levels 

The good news? There’s a lot you can do to support your testosterone levels naturally, especially if you're in the early stages of decline. Here are 5 tips to get you started: 

1. Prioritise deep sleep 

Aim for 7-9 hours of quality, consistent sleep. Poor sleep reduces luteinising hormone (LH), which signals the testes to produce testosterone.  

2. Train regularly

Lifting weights, particularly using compound movements like squats or deadlifts, triggers testosterone production more effectively than cardio alone. 

3. Eat nutrient-dense foods 

Support testosterone with foods rich in: 

• Zinc: shellfish (particularly oysters, pumpkin seeds, legumes 

• Magnesium: dark leafy greens, nuts, seeds 

• Healthy fats: avocado, olive oil, oily fish 

• Vitamin D: sunshine, mushrooms, or supplements* 

*I always advise getting your vitamin D level tested before supplementing. There’s a longer read about this here. 

4. Manage stress 

Chronic stress = chronic cortisol = suppressed testosterone. Mindfulness, breathwork, time outdoors, and adaptogens like ashwagandha may help reduce cortisol. 

5. Watch your alcohol intake 

Limit your intake to a few drinks a week. Alcohol can suppress testosterone and impair liver detox pathways, which play a key role in hormone balance. 

Final thoughts: don’t settle for ‘just getting older’ 

Declining testosterone is a natural part of ageing, but that doesn’t mean you’re powerless. If you’re over 40 and starting to feel the effects of low energy, reduced focus, or changes in body composition, it’s time to consider whether your hormones are working with you – or against you. 

A simple test and a few targeted lifestyle changes can help you reclaim your energy, confidence and performance.  

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Ready to find out if low testosterone is behind your symptoms? 

If you want to explore what’s really going on behind your symptoms, book a chat with me today.