“It's Just Age”: When Tiredness in Men Deserves a Proper Look

Quick answer

Tiredness with low mood, reduced libido and weight gain can be caused by thyroid disease, type 2 diabetes, sleep apnoea, iron or vitamin D deficiency, depression, medicines or genuine testosterone deficiency, and more than one often applies. Ask for an assessment with blood tests rather than accepting ageing as the explanation or assuming testosterone is the answer; replacement is not a treatment for tiredness when levels are normal. Seek prompt advice if you are falling asleep while driving, or if tiredness comes with unexplained weight loss.

Men in their forties and fifties often describe the same cluster: energy that collapses by mid-afternoon, less interest in sex, a shorter temper, poorer sleep, a waistband that has quietly moved. The usual verdict is that this is what getting older feels like. Some of it is — testosterone declines gradually with age, muscle is harder to hold on to, and sleep becomes lighter.

The difficulty with "it's just age" is that it is offered without a test, and it is indistinguishable from several conditions that are common, measurable and treatable. The pattern is non-specific: it points at a list rather than one diagnosis. That is a reason to look properly, not a reason to accept it.

It is equally not a reason to assume the problem is testosterone. The same four symptoms sell a great deal of hormone treatment to men who do not have a hormone problem. Dismissal and over-treatment are different mistakes with the same result: the real cause goes unaddressed.

What else produces this picture

Several conditions generate fatigue, low mood, reduced libido and weight change together, and more than one is often present.

Thyroid dysfunction. NICE advises testing where there is clinical suspicion, while noting that one symptom alone may not indicate thyroid disease. TSH is usually measured first, with free T4 added if TSH falls outside the reference range. NICE advises against testing during acute illness, because illness distorts the result.
Type 2 diabetes. The NHS lists feeling very tired among the common symptoms, alongside passing urine more often, persistent thirst and unintended weight loss, and is explicit that not everyone develops symptoms.
Obstructive sleep apnoea, which is both common and routinely missed.
Iron deficiency, with or without anaemia. In men this needs explaining rather than simply correcting: NICE recommends faecal immunochemical testing to guide referral for suspected colorectal cancer in adults with iron-deficiency anaemia.
Vitamin D deficiency. Severe deficiency causes bone pain through osteomalacia, and UK advice is a 10 microgram daily supplement in autumn and winter, with 100 micrograms the upper limit. Evidence that correcting mild deficiency relieves tiredness is weak, so we would not offer it as a sole explanation.
Depression, where the overlap runs both ways: NICE suggests considering thyroid tests in people with depression or unexplained anxiety rather than treating the diagnosis as settled.
Medicines. BSSM recommends screening for testosterone deficiency in men on long-term opioid, antipsychotic or anticonvulsant treatment, and a list of what you take is often more useful than any single blood test.
Testosterone deficiency, which is real, and has its own section below.

Why sleep apnoea deserves separate mention

NICE recommends taking a sleep history and assessing for obstructive sleep apnoea/hypopnoea syndrome in anyone with two or more of: snoring, witnessed apnoeas, unrefreshing sleep, waking headaches, unexplained sleepiness or tiredness, nocturia, choking during sleep, sleep fragmentation or insomnia, and cognitive or memory impairment.

Prevalence is higher in people living with obesity or overweight, type 2 diabetes, treatment-resistant hypertension, atrial fibrillation, hypothyroidism and acromegaly. NICE advises that the Epworth Sleepiness Scale should not be used alone to decide on referral, because not everyone with the condition feels sleepy. If you drive for a living, or hold a job where vigilance is critical for safety, NICE recommends sleep services prioritise you for rapid assessment.

Testosterone: what is established and what is not

Testosterone deficiency is a genuine diagnosis with a defined assessment. British Society for Sexual Medicine guidance advises measuring total testosterone between 7am and 11am, fasting, on at least two occasions and preferably four weeks apart, and basing decisions on published action levels rather than laboratory reference ranges. In that framework a total testosterone below 8 nmol/L usually requires treatment, above 12 nmol/L does not, and 8 to 12 nmol/L may justify a trial of at least six months based on symptoms. LH and FSH are added below 12 nmol/L, SHBG when the result is borderline or the man is older or carrying excess weight, and prolactin when LH and FSH are low.

What is not established is that testosterone treats tiredness in men whose levels are normal. In the Testosterone Trials, men over 65 with symptoms and a low measured testosterone received gel or placebo; sexual function improved modestly, while the vitality trial showed no significant benefit for fatigue. UK product information is correspondingly narrow: testosterone gel should be used only where hypogonadism has been demonstrated, other causes excluded, and deficiency confirmed by two separate blood measurements. Treatment also requires monitoring of haemoglobin and haematocrit for polycythaemia, along with prostate and breast, and large doses of exogenous androgen can reversibly suppress sperm production.

Where weight sits in this

Excess body fat is associated with lower measured testosterone, and BSSM recommends screening men with type 2 diabetes, a BMI above 30 or a waist above 102 cm. In July 2026 the Endocrine Society stated that where hypogonadism is appropriately diagnosed and relates to overweight or obesity, weight loss is typically first-line therapy; that symptoms alone are not diagnostic; and that labels such as "age-related" and "late-onset" hypogonadism blur the line between treatable disease and normal ageing. BSSM takes a different view for severely symptomatic men below 8 nmol/L, judging that lifestyle advice alone is unlikely to produce meaningful improvement. Expert bodies genuinely differ, and we would rather say so than imply the question is closed.

Why this field attracts bad information

Much of the marketing rests on a symptom checklist almost any tired man will meet. The safeguards are unglamorous: morning fasting samples, repeated, read alongside LH, FSH, SHBG and prolactin, with other causes excluded first. Gels also carry responsibilities beyond the man using them — the MHRA has warned that accidental skin-to-skin transfer has caused premature puberty and genital enlargement in children, and advises washing hands after application, covering the site once dry, and washing the area before close contact.

Tiredness in a middle-aged man is worth a blood test and a sleep history. It is rarely worth a hormone prescription obtained without either one.