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Low Testosterone Symptoms, Testing and Diagnosis

What Low T feels like, the number a blood test must show, and the other conditions that look exactly like it.

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Medically reviewed by David A. Robbins, MD — Diplomate, American Board of Urology Last reviewed November 2026

At a glance

The AUA uses a total testosterone level below 300 ng/dL as a reasonable cut-off in support of the diagnosis of low testosterone.
The diagnosis should be made only after two early-morning measurements on separate occasions; a single afternoon draw is not a diagnosis, and neither is a number without symptoms.
Low testosterone symptoms fall into four groups: sexual (decreased libido, erectile dysfunction), physical (lack of energy, decreased muscle mass and strength, decreased bone density), mood and thinking, and sleep.
Several common conditions produce the same symptoms, including sleep apnea, depression, thyroid disease, diabetes, obesity, some medications and heavy drinking.
The blood tests are ordered at your visit and drawn at an outside laboratory.

Symptoms

What low testosterone feels like

Low testosterone rarely announces itself. The changes tend to arrive slowly, and they are easy to put down to age, work or stress. The symptoms fall into four groups:

Sexual — decreased libido or sex drive, and erectile dysfunction.
Physical — lack of energy, easy fatigability or lack of endurance, decreased muscle mass and strength, and decreased bone density (osteoporosis).
Mood and thinking — depressed mood and impaired cognition.
Sleep — impaired sleep.

In Dr. Robbins’ words when this section was first written:

"Low testosterone and male andropause has become a hot topic over the past decade. Aging men with symptoms of low sex drive, decreased energy and muscle mass as well as erectile dysfunction are seeking a remedy for their complaints. These symptoms may be secondary to low testosterone. In addition to the symptoms of decreased energy and libido associated with low testosterone, patients may also be at risk for osteoporosis, decreased muscle mass, impaired cognitive ability and concentration, decreased exercise tolerance and even metabolic syndrome and impaired heart health. If you are experiencing any of the above symptoms, please contact us or your current urologist to have your testosterone levels evaluated."

You are reading a page written and reviewed by David Robbins, MD, a board-certified urologist (Diplomate, American Board of Urology) who has practiced in Miami since 2009 at a practice serving South Florida for more than four decades.

Causes

Why testosterone falls

The prescribing information for testosterone products sorts the recognised causes into two groups.

Primary — a problem in the testicles themselves. The labels list undescended testicles (cryptorchidism), torsion, orchitis, removal of the testicles (orchiectomy), Klinefelter syndrome, chemotherapy, and toxic damage from alcohol or heavy metals.

Secondary — a problem in the signal from the brain. Here the testicles are capable, but the pituitary gland or hypothalamus is not telling them to work, for example after injury from tumours, trauma or radiation.

Then there is the gradual decline that comes with age, which the overview page describes. Every FDA-approved testosterone product carries the same limitation: its safety and effectiveness in men with age-related ("late-onset") low testosterone have not been established. That does not mean such men are never treated — the AUA guideline supports treating men with a low level and symptoms — but it is why a urologist looks for the cause, not just the number.

Patients with chronic medical conditions such as diabetes, HIV/AIDS, chronic narcotic use, and chronic steroid use have a higher risk for a testosterone deficiency. And many possible causes of the same symptoms are not related to testosterone at all, such as diabetes, obesity, hypothyroidism, and other chronic medical conditions — which is where the testing comes in.

Sources: FDA prescribing information for testosterone products (Indications and Usage; e.g. AndroGel 1.62%, label dated 30 Sep 2024); American Urological Association, Evaluation and Management of Testosterone Deficiency (2018; validity confirmed 2024).

Testing

What counts as low

The American Urological Association uses a total testosterone level below 300 ng/dL as a reasonable cut-off in support of the diagnosis — and says the diagnosis should be made only after two measurements on separate mornings. A single afternoon draw is not a diagnosis; neither is a number without symptoms.

The AUA cut-off, on a scale

Total testosterone 300 ng/dL

At the AUA cut-off used to support a diagnosis of low testosterone.

The AUA uses a total testosterone below 300 ng/dL as a reasonable cut-off in support of the diagnosis, made only after two early-morning measurements on separate occasions. Laboratories publish their own reference ranges; a number without symptoms is not a diagnosis, and this scale is not one either.

Along with total testosterone, the evaluation may include free testosterone, SHBG, PSA, and pituitary hormones such as LH, FSH and prolactin, plus a blood count and liver function — the same panel described on the overview page. The blood tests are ordered at your visit and drawn at an outside laboratory.

Source: American Urological Association, Evaluation and Management of Testosterone Deficiency (2018; validity confirmed 2024), statements 1 and 2.

The look-alikes

Not every symptom is Low T

Tiredness, low drive, poor sleep and low mood are real, and they deserve an explanation. But each of them has more than one possible cause, and several common conditions produce the same picture:

Sleep apnea — broken sleep at night can look like low energy by day.
Depression — low mood, low energy and low desire often travel together.
Thyroid disease — an underactive thyroid (hypothyroidism) can cause fatigue.
Diabetes — one of the chronic conditions that can cause the same symptoms.
Obesity — another, and one that is often part of the same conversation. It is also one of the causes that can reverse: testosterone tends to rise as weight comes down.
Medications — including chronic narcotic (opioid) use and chronic steroid use.
Alcohol — heavy drinking affects energy, sleep and sexual function.

That is why the evaluation looks at the whole picture and not only at one blood result. A level that isn’t low is an answer too, and we’ll say so.

A common reason men come in

Low sex drive: testosterone is one cause, not the only one

A drop in desire is one of the most common reasons men ask about testosterone, and it is a fair question to ask. Low testosterone can lower sex drive. So can stress, depression, poor sleep, alcohol, relationship strain and some medications — and erection problems can wear desire down too.

So testosterone is checked, and so is the rest. If the level is low and the symptoms fit, treatment is a reasonable conversation, and the treatment options page sets out every form it can take. If erections are the bigger part of the problem, the erectile dysfunction page covers that side.

Straight answers

Frequently Asked Questions

Is it Low T?

Only a blood test can say. The symptoms above are real, but each of them has other causes. If you recognise several of them, the first step is a morning total testosterone level — and if it is low, a second one on another morning.

What is a normal testosterone level?

Laboratories publish their own reference ranges, so "normal" varies slightly by lab. The AUA uses a total testosterone below 300 ng/dL as a reasonable cut-off in support of the diagnosis. Where treatment is given, the guideline’s target is the middle third of the normal range — not the top of it.

Why does the test have to be in the morning?

In the AUA guideline’s own words, the most accurate testosterone measurements are obtained in the early morning and on more than one occasion. That is why the diagnosis rests on two early-morning draws, taken on separate days.

Can low testosterone cause erectile dysfunction?

It can contribute, and the two often travel together, but most erectile dysfunction has vascular or other causes. Testosterone is one part of an ED evaluation, not the whole of it. Every ED treatment, explained.