Signs of Low Testosterone: What to Look For

Low testosterone gets blamed for almost everything a man over 35 dislikes about himself: the tiredness, the softer midsection, the flatter mood, the weaker erections. Some of that is fair. A lot of it is not, and chasing the wrong explanation costs months.

The useful version of this question is narrower. Which signs actually predict a low blood test, which ones are noise, and what do you do with the answer.

What Low Testosterone Actually Means

Testosterone deficiency is a diagnosis with two halves, and both are required. The American Urological Association's testosterone deficiency guideline sets the threshold at a total testosterone consistently below 300 ng/dL on at least two early-morning measurements, combined with the presence of symptoms.

The morning part matters more than most men realise. Testosterone follows a daily rhythm, peaking in the early hours and drifting down through the day. A blood draw at 4pm can put a perfectly normal man under the threshold. Two morning draws, ideally a couple of weeks apart, is the standard for a reason.

The second half — symptoms — is what stops the number becoming meaningless. Plenty of men sit below 300 ng/dL and feel entirely fine. A low number with no symptoms is a lab result, not a condition.

The Signs That Point at Testosterone

Grouping the symptoms by how strongly they point at a hormone problem is more useful than listing them alphabetically.

Strongest signals — sexual:

• Loss of sex drive. The single most specific symptom. Not "less interested than at 22," but a clear drop from your own recent baseline, sustained over months.
• Fewer spontaneous erections, especially the morning ones. Testosterone drives the reflexive, non-erotic erections that happen during sleep.
• Reduced ejaculate volume and a duller, less intense orgasm.
• Erectile difficulty — real, but the least specific of the four, for reasons covered below.

Moderate signals — physical:

• Fat gain around the abdomen, particularly alongside muscle loss despite unchanged training.
• Strength plateauing or reversing when nothing about your training or diet has changed.
• Reduced body and facial hair growth.
• Breast tissue tenderness or enlargement.
• Hot flushes — uncommon, but quite specific when they appear in a man.

Weak signals — general:

• Fatigue, low motivation, irritability, brain fog, low mood, poor sleep.

The StatPearls clinical review of male hypogonadism lists all of these, and the general symptoms are genuinely part of the picture. The problem is that they are also the presentation of poor sleep, depression, thyroid disease, anaemia, iron deficiency, sleep apnoea and simply being under-recovered. On their own they justify a blood test. They do not justify a conclusion.

How Common Is It

Common enough that the question is reasonable to ask. Mulligan and colleagues ran the HIM study across 2,162 men aged 45 and over attending primary care and reported a 38.7% prevalence of hypogonadism, published in the International Journal of Clinical Practice in 2006. Odds were roughly double in men with obesity or diabetes, and substantially raised in men with hypertension.

That last point reframes the whole topic. Low testosterone tracks metabolic health closely enough that in many men it is downstream of body composition rather than an independent event.

Travison and colleagues put a number on it in the Journal of Clinical Endocrinology and Metabolism in 2007, analysing the Massachusetts Male Aging Study cohort: a 4 to 5 kg/m² rise in BMI produced a decline in total testosterone comparable to about ten years of ageing. Losing a stone is not a hormone treatment, but it is not nothing either.

The Symptom Most Men Get Wrong

Erectile difficulty is the sign that sends most men searching for testosterone answers, and it is the one most likely to send them down the wrong path.

Testosterone drives desire. Erections are largely a matter of blood flow and mechanics — arterial inflow, and the pelvic floor muscles that compress the deep dorsal vein to trap blood in the penis and keep it there. Those two systems overlap, but they are not the same system.

The practical distinction:

• Desire has dropped and erections have followed — the pattern most consistent with low testosterone. Get the blood test.
• Desire is intact but firmness is not — the pattern of a vascular, pelvic or psychological cause. A normal testosterone result here is common and, crucially, does not mean nothing is wrong.

The second pattern is where pelvic floor training has genuine evidence behind it. Dorey and colleagues randomised men with erectile dysfunction to pelvic floor muscle exercises versus lifestyle advice in BJU International in 2004, and at six months 40% had regained normal erectile function with a further 35.5% significantly improved. That trial had nothing to do with hormones. Kegels for men covers the mechanism in full, and what causes a man to erect fast walks through the erection reflex itself.

Getting Tested Properly

If two or more of the strong signals have been present for several months, get the blood work. What to ask for and how to make it count:

1. Total testosterone, drawn between 7am and 10am. Non-negotiable timing.
2. A second confirmatory draw on a different morning before accepting any result.
3. Free or bioavailable testosterone plus SHBG if the total sits in the borderline 250–400 ng/dL band. Sex hormone binding globulin rises with age and can leave usable testosterone low while the total looks acceptable.
4. LH and FSH, which separate a testicular problem from a pituitary one and change what happens next.
5. Prolactin, thyroid function, ferritin and a full blood count — the usual suspects behind the same general symptoms.

Do not test during an acute illness or immediately after a period of severe sleep deprivation. Both suppress testosterone temporarily and produce a low reading that means nothing about your baseline. Harvard Health's overview of what testosterone does and does not do is a sober counterweight to most of what is written about it online.

What Progress Looks Like

If the diagnosis is confirmed and treatment starts, the timeline is uneven. Sex drive and mood typically respond first, over roughly three to six weeks. Body composition changes take three to six months. Erectile function, if it improves, is usually the slowest and least complete of the three — another sign that firmness is not primarily a hormone problem.

If the tests come back normal, that is information rather than a dead end. It redirects attention to sleep, training load, alcohol, body composition, and the pelvic and vascular contributors to erection quality. Low testosterone symptoms in men goes further into the symptom picture, and how to increase libido in men covers the non-hormonal levers on desire.

The Short Version

The signs worth acting on are sexual and specific: desire falling away, morning erections disappearing, ejaculate volume dropping, orgasm flattening. Fatigue and low mood earn you a blood test, not a conclusion. The threshold is under 300 ng/dL on two morning draws with symptoms present, and body composition moves the number more than almost anything else you control.

And if desire is fine while firmness is not, the answer is probably not in your bloodwork at all.