BSc (Hons), RNMH, NMP

Advanced nurse practitioner

Low testosterone, often shortened to low T, is a common condition that can affect energy, mood, sexual health, and physical wellbeing. Low T symptoms are frequently subtle, making it difficult to recognise without proper testing. This guide explains how to know if you have low testosterone and the best ways to treat it.

What does testosterone do?

Testosterone, like other hormones, maintains a wide range of functions. It influences your sex drive, contributes to muscle maintenance, helps regulate body fat, and supports mental focus and motivation. It’s also essential for strong bones and producing red blood cells. When levels start to dip, it’s often the combination of changes to energy, mood, strength, or libido, that people notice first.

Low T symptoms

Low testosterone can affect men in many ways, and the changes often develop gradually enough that they’re easy to overlook. It’s widely acknowledged that men tend to attribute these changes to ageing or stress, meaning low T often goes undiagnosed for longer than it should [1]. Understanding the broader picture of how testosterone influences the body makes it easier to recognise when something might be out of balance and when testing could be worthwhile.

Sexual symptoms

Sexual symptoms are often the most apparent signs of men’s low testosterone [2].

Low libido
Erection difficulties
Fewer morning erections
Reduced semen volume

Physical symptoms

Reduced muscle mass or strength
Increased body fat (particularly abdominal)
Low energy or persistent fatigue
Reduced exercise performance
Loss of body hair or slower beard growth

Psychological and cognitive symptoms

Low mood or irritability
Poor concentration
Reduced motivation
Sleep disturbances

Experiencing several of these symptoms together may indicate low testosterone and warrant further investigation.

Read our guide to low testosterone for more information.

Men’s testosterone range

In the UK, testosterone is measured as total testosterone in nmol/L, and although ranges vary slightly by laboratory, as a guide, typical healthy male testosterone levels are:

Age group	Men’s normal testosterone levels (nmol/L) [3]
2–10	<0.24–0.35
11–15	<0.24–26.25
16–17	7.92–27.0
18–49	8.7–29.0
50+	6.7–25.7

The testosterone level for a healthy adult man should be around 8.7–29 nmol/L; however, if it drops below 12 nmol/L, and you show signs of having low T, you may benefit from testosterone replacement therapy (TRT).

How to know if you have low testosterone

A diagnosis of low testosterone requires:

Symptoms consistent with low testosterone
Two separate morning blood tests (preferably 3-4 weeks apart) showing low T levels

When should you take your blood test?

Testosterone levels tend to rise overnight and peak in the early morning. The body’s natural rhythm largely guides this pattern. While you sleep, especially during REM, the brain prompts the testes to boost testosterone production, which is why levels are usually highest first thing in the morning (2). As the day goes on, those levels slowly taper off, making morning tests the most reliable way to get an accurate reading.

To help identify underlying causes and rule out other medical conditions, blood tests may also check:

Sex hormone binding globulin (SHBG)

Luteinising hormone (LH) and follicle-stimulating hormone (FSH)

Prolactin

Thyroid function

Blood count

How to check for low testosterone

Several straightforward options are available to check for low testosterone, depending on whether you prefer testing at home or through a healthcare provider.

Testosterone home test

A testosterone check at home uses a finger-prick blood sample which is posted to a laboratory for analysis. This can be a convenient first step if you want to screen your levels privately.

Look for tests that include at a minimum:

Free testosterone: Free testosterone is the amount of testosterone in the blood that isn’t bound to proteins and is therefore biologically active

Total testosterone: This is the full amount of testosterone in the blood, including free and bound T

SHBG

A doctor-reviewed result offered by some at-home tests should provide guidance and actionable next steps.

Clinic-based testosterone testing

A medical clinic can offer:

Venous blood tests

Repeat testing for diagnostic accuracy

Clinical review of symptoms

Guidance on treatment options if levels are consistently low

Clinics specialising in men’s health can also investigate sleep, lifestyle, and metabolic factors that influence hormones.

What is TRT for men?

TRT is a medically supervised treatment for men with confirmed low testosterone. It aims to restore testosterone to a healthy range, which can improve any symptoms you may be experiencing.

TRT is generally recommended only when symptoms and blood test results meet the established clinical criteria.

How to get TRT

If your symptoms and test results suggest low testosterone, the next step is understanding how treatment is accessed and prescribed. The process is straightforward, but it does involve proper assessment and medical guidance to ensure TRT is safe, appropriate, and tailored to your needs.

Clinical assessment

A clinical assessment is an essential step in determining whether TRT is suitable for you and involves a thorough review of your overall health, including your symptoms, blood test results, and medical history. They’ll also explore any factors that could be contributing to low T, such as obesity, high stress levels, or underlying health conditions. This ensures the correct diagnosis is made and that any treatment plan is both safe and genuinely needed.

Discuss treatment options

If TRT is considered appropriate, your clinician will talk you through the different treatment options, such as injections, gels, or capsules, what to expect, and the potential benefits you may experience. In addition, they will discuss possible risks and side effects so that you can make an informed decision about your care.

Ongoing monitoring

Once treatment begins, regular monitoring makes sure that TRT remains safe and effective. Follow-up blood tests are performed at set intervals to ensure that testosterone levels are within a healthy range and that key safety markers, such as blood counts and, where appropriate, prostate-specific antigens (PSA), remain stable. This ongoing review allows your clinician to adjust treatment if needed and helps maintain long-term safety.

Low testosterone can have a noticeable impact on how you feel day to day, but it’s a condition that’s both easy to check and manageable with the proper support. Understanding the symptoms, knowing when to test, and seeking appropriate medical guidance can help you take control of your health and improve your overall wellbeing.