Signs Your Testosterone Is Low After 40 — And What to Do

Most men don't walk into a doctor's office and say "I think my testosterone is low." They say they're tired all the time. They say they've lost their drive. They say the training isn't working the way it used to, and the weight won't move no matter what they do. Then they get told it's stress, or age, or that they need to sleep more. Sometimes that's true. Sometimes it isn't.

Low testosterone — defined clinically as total testosterone below 300 ng/dL — affects an estimated 40% of men over 45. Many of them don't know because the symptoms overlap with half a dozen other things and most standard GP check-ups don't include a testosterone panel. Here's what to actually look for.

The Real Symptoms — Not the Obvious Ones

The obvious symptoms (low libido, erectile dysfunction) get most of the attention because they're the ones supplement companies advertise against. But for most men, the first signs are more subtle:

• Persistent fatigue despite adequate sleep — not tiredness that responds to rest, but a flat, unresponsive energy level that doesn't improve much even after a good night's sleep
• Loss of competitive drive and motivation — reduced ambition, less interest in goals, a general flatness that feels more like a personality shift than a mood episode
• Training plateau that doesn't respond to changes in program — you're working as hard as before but muscle gains have stalled and recovery takes noticeably longer
• Accumulation of belly fat despite no change in eating — visceral fat increases when testosterone drops, independent of calories, due to changes in how the body partitions energy
• Joint aches and reduced recovery — testosterone has anti-inflammatory effects; lower levels mean slower repair and more soreness between sessions
• Brain fog and reduced sharpness — word-finding difficulties, slower thinking, reduced ability to focus on complex tasks
• Reduced morning erections — this is one of the more reliable physiological markers; frequency and firmness of morning erections correlates directly with testosterone levels

What to Do: The Exact Steps

Step 1 — Get a blood test. Ask specifically for: total testosterone, free testosterone, LH (luteinising hormone), FSH, SHBG (sex hormone binding globulin), and oestradiol. Some GPs will only order total testosterone — push for the full panel. Free testosterone is often more clinically relevant than total testosterone for symptoms.

Step 2 — Test at the right time. Testosterone is highest in the morning, typically peaking between 7–10am. Always get your blood drawn in the morning for an accurate reading. Afternoon tests can show levels 20–30% lower than morning levels in the same person on the same day.

Step 3 — Apply lifestyle interventions first. If your levels are low-normal (300–450 ng/dL) rather than clinically deficient, lifestyle changes alone can produce meaningful increases. The four most evidence-backed: resistance training 3x per week, 7–9 hours of sleep, reducing body fat, and managing chronic stress. Give these 8–12 weeks before reassessing.

Step 4 — If clinically deficient, discuss TRT with a specialist. Not a GP with limited endocrinology experience — a urologist or endocrinologist who manages testosterone regularly. TRT is effective and appropriate for many men over 45 with confirmed deficiency and symptoms. It should be a medically supervised, properly monitored decision — not a shortcut to feeling better or building more muscle.

What Not to Do

Don't self-supplement with over-the-counter testosterone boosters. The vast majority of products sold in this category have no meaningful effect on testosterone levels. The handful with any evidence (vitamin D, zinc, ashwagandha) work only in deficient men and produce modest results — nothing close to actual TRT or even the lifestyle interventions above.

Don't catastrophise a single low reading. Testosterone fluctuates with sleep, stress, illness, and alcohol consumption. One low test doesn't diagnose hypogonadism. Most endocrinologists require two separate morning readings below 300 ng/dL before considering treatment.

The most important thing: get the data. Operating on symptoms alone keeps you guessing. A blood test takes 10 minutes and gives you an actual number to work with.