TESTOSTERONE
How testosterone changes after 40 (and what actually helps)
Testosterone does drift down with age, but slowly. Weight, sleep and general health shape how steep that decline is.
Yes, testosterone usually falls after 40, but gradually: long-term studies put the drop in total testosterone at roughly 1 to 2% a year, with the freely available fraction falling a little faster.1 What surprises most men is how much of the difference between individuals comes down to body weight, sleep and general health, which are things you can do something about.
Total testosterone falls slowly with age, around 1.6% a year within the same men in one large US study, while free and bioavailable testosterone fall faster.
A low number on its own is not a diagnosis; doctors look for a consistent pattern of symptoms plus repeated, clearly low morning blood tests.
Of all the symptoms blamed on low testosterone, the sexual ones (low desire, fewer morning erections, erection problems) track it most closely.
Losing excess weight is the lifestyle change with the strongest evidence for raising testosterone, and the more weight lost, the bigger the rise.
Short sleep lowers testosterone within a week, so sleep is one of the cheapest things to fix first.
Testosterone therapy helps men with genuinely low levels and symptoms, but it is not an anti-ageing treatment and it shuts down sperm production.
How much does testosterone drop after 40?
For most men, total testosterone falls by roughly 1 to 2% a year from middle age, and free testosterone falls faster because a binding protein rises with age. The decline is gradual rather than a sudden ‘male menopause’, and the range between individual men is wide.
The best numbers come from studies that followed the same men for years. The Massachusetts Male Aging Study measured more than a thousand men aged 40 to 70 and then again 7 to 10 years later. Within the same men, total testosterone fell by about 1.6% a year and bioavailable testosterone by 2 to 3% a year.1
The Baltimore Longitudinal Study of Aging, which analysed stored blood from 890 men, found a steady average fall of about 0.124 nmol/L a year in total testosterone, alongside a fall in the free testosterone index.2 The share of men with hypogonadal levels climbed with each decade: roughly 20% of men over 60, 30% over 70 and 50% over 80 on total testosterone criteria.2
Why free testosterone falls faster than total
Most testosterone in the blood is bound to proteins, chiefly sex hormone-binding globulin (SHBG). SHBG rises with age (by about 1.6% a year in the Massachusetts cohort), so even when total testosterone looks acceptable, the unbound portion your tissues can use, called free testosterone, may be falling more steeply.1 That is why a doctor may ask for a free testosterone estimate when a result sits near the lower limit.
Study
Who was followed
Main finding on ageing
Massachusetts Male Aging Study
1,156 men aged 40-70, retested after 7-10 years
Total T fell about 1.6% a year within men
Baltimore Longitudinal Study of Aging
890 men, stored samples over decades
Total T fell about 0.124 nmol/L a year
European Male Ageing Study (follow-up)
2,395 men aged 40-79, retested after 4.4 years
Weight gain lowered T; weight loss raised it
European Male Ageing Study (symptoms)
3,369 men aged 40-79
Sexual symptoms tracked low T most closely
Is falling testosterone just ageing, or is something else going on?
Both. Age itself lowers testosterone a little every year, but obesity, chronic illness, some medicines and heavy drinking lower it further. Men in good general health tend to have noticeably higher levels than men of the same age who are not.
In the Massachusetts study, men in ‘apparent good health’, defined as no chronic illness, no prescription medication, no obesity and no excessive drinking, had levels of several androgens 10 to 15% higher than other men.1 The researchers suggested that new health problems arriving in midlife may speed up the fall.1
The Baltimore data pull in the other direction slightly: they found an age-related decline even after accounting for health factors, which means some drop is simply part of getting older.2 The practical reading: you cannot stop the clock, but you can influence how steep the slope is.
What symptoms actually point to low testosterone after 40?
The symptoms most closely linked to low testosterone are sexual: low sex drive, fewer morning erections and erection problems. Tiredness, low mood and reduced vigour are also associated, but they are common for many other reasons and are much less specific.
The European Male Ageing Study surveyed 3,369 men aged 40 to 79 and measured testosterone accurately in morning blood samples. Poor morning erections, low sexual desire, erectile dysfunction, inability to do vigorous activity, depression and fatigue were all related to testosterone level, but only the three sexual symptoms clustered together with low testosterone in a way that looked like a genuine syndrome.3
Based on that, the researchers proposed that late-onset hypogonadism be defined by at least three sexual symptoms alongside total testosterone below 11 nmol/L and free testosterone below 220 pmol/L.3 The principle matters more than the numbers: fatigue alone is rarely explained by testosterone. Faded morning erections plus lower desire are more worth checking.
Quick self-check: could it be worth a testosterone test?
I rarely wake with an erection any more, when I used to regularly.
My interest in sex has dropped noticeably over the past year or so.
I have more trouble getting or keeping an erection than I used to.
I feel physically weaker or less able to do vigorous exercise.
I have gained a lot of weight around my middle in recent years.
I regularly sleep fewer than six hours a night.
I have been feeling persistently low or flat.
Tap the statements that apply to you.
If several of these apply, especially the first three, it is reasonable to ask your GP about a morning testosterone test. The sexual health check can help you organise what to mention.
Does losing weight raise testosterone?
Yes. Weight loss is the lifestyle change with the strongest evidence behind it: studies of both diet and weight-loss surgery show testosterone rises as weight falls, and the more weight lost, the larger the rise. Weight gain has the opposite effect.
The follow-up of the European Male Ageing Study retested 2,395 men about four years after their first visit. Weight loss was linked to a proportional rise in testosterone and SHBG, and weight gain to a proportional fall.4 Free testosterone behaved differently: it only changed meaningfully in men who gained or lost at least 15% of their body weight.4
“Weight management appears to be important in maintaining circulating testosterone in ageing men, and obesity-associated changes in HPT axis hormones are reversible following weight reduction.”
A meta-analysis of 24 studies reached the same conclusion from the treatment side. Both low-calorie diets and bariatric surgery raised total testosterone, by an average of 2.87 nmol/L with diet and 8.73 nmol/L with surgery, and the amount of weight lost was the best predictor of how much testosterone rose.5 Weight loss also lowered oestradiol and raised the pituitary hormones that drive the testes, which fits with the idea that excess fat itself suppresses the hormone system.5
How much do sleep, exercise and alcohol affect testosterone after 40?
Sleep matters quickly: one week of five-hour nights measurably lowered daytime testosterone in young men. Exercise is valuable for muscle, weight and erections but changes in activity have not been shown to shift testosterone much on their own. Heavy drinking is one of the factors linked to lower levels.
Sleep
In a laboratory study, ten healthy young men spent three nights with ten hours in bed and then eight nights restricted to five hours. After a week of short sleep, their daytime testosterone averaged 16.5 nmol/L against 18.4 nmol/L when rested, and their self-rated vigour fell night by night.6 That was a young, healthy group, which is one reason the link between sleep and sex drive deserves more attention than it gets.
Exercise
Exercise is often sold as a testosterone booster, but in the European ageing follow-up, changes in physical activity were not linked to meaningful changes in testosterone or related hormones.4 Training is still worthwhile: resistance work preserves muscle, activity helps with weight loss (which does raise testosterone), and aerobic fitness helps blood flow, which is why cardio can improve erections regardless of hormones.
Alcohol and smoking
Excessive drinking was one of the factors used to separate the ‘apparently healthy’ men, who had 10 to 15% higher androgen levels, from everyone else in the Massachusetts study.1 Smoking is a curious case: in the European data, men who quit saw a larger fall in testosterone than lifelong non-smokers, independent of weight change.4 That is no reason to keep smoking, which damages blood vessels and erections.
Myth or fact?
Myth: Every man over 40 has low testosterone.
Fact: Levels fall gradually, and low results become more common with each decade rather than universal. In one long-term study, around 20% of men over 60 had hypogonadal total testosterone, rising to about 30% over 70.2
Myth: Tiredness after 40 is probably low testosterone.
Fact: Fatigue is linked to testosterone, but in the largest European study it did not cluster with low testosterone the way sexual symptoms did.3 Sleep, mood, thyroid problems and many other things cause tiredness.
Myth: Hard training is the best way to raise testosterone.
Fact: Exercise is excellent for health, but changes in physical activity were not linked to meaningful hormone changes in ageing men. Weight loss had the clearer effect.4
Myth: Testosterone therapy is an anti-ageing treatment.
Fact: In men aged 65 and over with low levels, a year of treatment helped sexual function and mood a little but did not improve vitality or walking distance.7
What have studies found on supplements for testosterone after 40?
A handful of supplement ingredients have been tested in randomised trials in men, and results have varied depending on the ingredient and on who was studied. Research is ongoing, so it helps to look at each trial's population and outcomes rather than the label's promises.
In a 16-week crossover trial that enrolled 57 overweight men aged 40 to 70 with mild fatigue, 8 weeks of a standardised ashwagandha extract was associated with an 18% greater rise in DHEA-S and a 14.7% greater rise in salivary testosterone than placebo. Fatigue, vigour and sexual well-being improved over time in both groups, without a significant difference between them, and the authors called for larger studies.8
Vitamin D contributes to the maintenance of normal muscle function. Its link with testosterone has also been studied: in a 12-week trial of 98 healthy men with normal testosterone and vitamin D levels below 75 nmol/L, weekly vitamin D3 did not change total testosterone compared with placebo.9 Zinc contributes to the maintenance of normal testosterone levels in the blood, and our guide to supplements with evidence covers zinc, tongkat ali and other ingredients in more detail.
If you take prescribed medicines, check with a pharmacist or GP before adding a supplement. If you have symptoms, a blood test is still the place to start.
When should you get your testosterone tested?
Get tested if you have symptoms, particularly sexual ones, that have lasted for months. The test should be a fasting blood sample taken in the morning, and a low result should be repeated before anyone makes a diagnosis.
The Endocrine Society recommends diagnosing low testosterone only in men who have both symptoms and signs of deficiency and levels that are ‘unequivocally and consistently’ low. It recommends a fasting morning total testosterone as the first test, a repeat to confirm, and a free testosterone estimate if the result is borderline or SHBG is likely to be abnormal.10
Timing matters. In a Boston study of men aged 30 to 80, testosterone in men in their 30s was 20 to 25% lower at 4pm than at 8am, and the gap narrowed to about 10% by age 70. Some men who looked low in the afternoon were normal at every morning visit.11 If your only result came from an afternoon appointment, ask for a morning retest.
When to see a doctor
See your GP if you have lost interest in sex, rarely have morning erections or have new erection problems that have lasted a few months, especially if you also feel weaker, flatter or more tired than you used to.
Seek advice sooner if you notice breast swelling or tenderness, shrinking testicles, hot flushes, a loss of body hair, or if you have had a head injury, pituitary problem or cancer treatment. These can point to other causes worth investigating.
Mention erection problems even if your testosterone turns out to be fine: they can be an early sign of heart and blood vessel disease.
Is testosterone therapy worth it for men over 40?
For men with clearly low levels and symptoms, testosterone therapy can improve sex drive, sexual activity and mood modestly. It does not reliably restore energy or physical function, it suppresses sperm production, and it needs monitoring, so it is a medical decision rather than a lifestyle upgrade.
The Testosterone Trials gave 790 men aged 65 and over, with testosterone below 275 ng/dL (about 9.5 nmol/L) and symptoms, either testosterone gel or placebo for a year. Treatment raised levels to the mid-normal range for young men and moderately improved sexual activity, sexual desire and erectile function, with some benefit to mood. It did not improve vitality or walking distance.7
The TRAVERSE trial followed 5,246 men aged 45 to 80 with low testosterone and existing heart disease or high cardiovascular risk. Major cardiac events occurred in 7.0% of men on testosterone and 7.3% on placebo, so therapy was not worse for the heart overall, though atrial fibrillation, acute kidney injury and pulmonary embolism were more common in the testosterone group.12
Guidelines are clear about who should not start testosterone replacement: men planning to have children in the near term, men with breast or prostate cancer or certain prostate findings, a raised red blood cell count, untreated severe sleep apnoea, uncontrolled heart failure or a recent heart attack or stroke.10 The fertility point catches many men out, because external testosterone switches off the signals the testes need to make sperm. If children are still on the cards, our guide to how long sperm take to regenerate explains the timescales involved.
Frequently asked questions
At what age does testosterone start to decline?
Population studies suggest a gradual decline from around middle age, with long-term data in men aged 40 to 70 showing total testosterone falling by roughly 1.6% a year.1 There is no single switch-off point.
What is a normal testosterone level for a man over 40?
Reference ranges vary by laboratory and assay, so compare your result with the range printed on your report. The European Male Ageing Study used total testosterone below 11 nmol/L, together with sexual symptoms and a low free testosterone, to identify late-onset hypogonadism.3
Can you raise testosterone naturally after 40?
Yes, within limits. Losing excess weight has the strongest evidence, with bigger losses producing bigger rises.5 Protecting sleep and keeping alcohol moderate help too.
Will testosterone therapy make me infertile?
It can. Testosterone therapy suppresses the hormones that drive sperm production, which is why guidelines advise against starting it in men planning fertility in the near term.10 Speak to a doctor about alternatives if children are part of your plans.
Does testosterone therapy cause heart attacks?
The largest trial so far, in men with low testosterone and high cardiovascular risk, found no increase in major cardiac events compared with placebo, though some other problems, including atrial fibrillation, were more common.12 It still requires monitoring and an individual discussion of risks.
[1] Feldman HA, et al. Age trends in the level of serum testosterone and other hormones in middle-aged men: longitudinal results from the Massachusetts male aging study. J Clin Endocrinol Metab. 2002;87(2):589-98. PubMed
[2] Harman SM, et al. Longitudinal effects of aging on serum total and free testosterone levels in healthy men. Baltimore Longitudinal Study of Aging. J Clin Endocrinol Metab. 2001;86(2):724-31. PubMed
[3] Wu FC, et al. Identification of late-onset hypogonadism in middle-aged and elderly men. N Engl J Med. 2010;363(2):123-35. PubMed
[4] Camacho EM, et al. Age-associated changes in hypothalamic-pituitary-testicular function in middle-aged and older men are modified by weight change and lifestyle factors: longitudinal results from the European Male Ageing Study. Eur J Endocrinol. 2013;168(3):445-55. PubMed
[5] Corona G, et al. Body weight loss reverts obesity-associated hypogonadotropic hypogonadism: a systematic review and meta-analysis. Eur J Endocrinol. 2013;168(6):829-43. PubMed
[6] Leproult R, et al. Effect of 1 week of sleep restriction on testosterone levels in young healthy men. JAMA. 2011;305(21):2173-4. PubMed
[7] Snyder PJ, et al. Effects of Testosterone Treatment in Older Men. N Engl J Med. 2016;374(7):611-24. PubMed
[8] Lopresti AL, et al. A Randomized, Double-Blind, Placebo-Controlled, Crossover Study Examining the Hormonal and Vitality Effects of Ashwagandha ( Withania somnifera) in Aging, Overweight Males. Am J Mens Health. 2019;13(2):1557988319835985. PubMed
[9] Lerchbaum E, et al. Vitamin D and Testosterone in Healthy Men: A Randomized Controlled Trial. J Clin Endocrinol Metab. 2017;102(11):4292-4302. PubMed
[10] Bhasin S, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(5):1715-1744. PubMed
[11] Brambilla DJ, et al. The effect of diurnal variation on clinical measurement of serum testosterone and other sex hormone levels in men. J Clin Endocrinol Metab. 2009;94(3):907-13. PubMed
[12] Lincoff AM, et al. Cardiovascular Safety of Testosterone-Replacement Therapy. N Engl J Med. 2023;389(2):107-117. PubMed
Eric Stephens
Eric Stephens writes and edits every guide on Load Boosting. He reads and summarises peer-reviewed research and major medical-society guidance on men’s health, and links to every source.