Key Points
- Testosterone naturally declines with age — this is normal
- True testosterone deficiency (hypogonadism) is less common than many think
- Many symptoms attributed to "low T" have other causes
- Testosterone replacement is only appropriate for men with proven deficiency
- Buying testosterone online without a prescription is illegal and dangerous
What Does Testosterone Do?
Testosterone is the main male sex hormone. It's responsible for:
- Development of male characteristics during puberty
- Muscle mass and strength
- Bone density
- Sex drive (libido)
- Sperm production
- Red blood cell production
- Fat distribution
- Mood and energy
Testosterone levels naturally decline by about 1-2% per year after age 30. This is normal and doesn't usually cause problems.
Symptoms of Low Testosterone
True testosterone deficiency (hypogonadism) can cause:
Sexual Symptoms
- Reduced sex drive
- Erectile dysfunction
- Fewer spontaneous erections
- Reduced fertility
Physical Symptoms
- Loss of muscle mass
- Increased body fat
- Decreased bone density
- Fatigue
- Breast tissue development
Mental Symptoms
- Low mood
- Poor concentration
- Reduced motivation
- Sleep disturbances
Other Signs
- Hot flushes
- Reduced body hair
- Small testicles
- Anaemia
Important Note
These symptoms are very non-specific. They're commonly caused by:
- Depression and anxiety
- Poor sleep
- Obesity
- Diabetes
- Other medical conditions
- Normal ageing
Don't assume your symptoms are due to low testosterone without proper testing.
Causes of Low Testosterone
Primary Hypogonadism
Problem with the testicles
- Klinefelter syndrome
- Undescended testicles
- Testicular injury
- Cancer treatment
- Mumps orchitis
Secondary Hypogonadism
Problem with pituitary/hypothalamus
- Pituitary tumour
- Obesity
- Type 2 diabetes
- Opioid use
- Steroid use
- Chronic illness
Testing for Low Testosterone
If your GP suspects low testosterone, they'll arrange blood tests:
How Testing Works
- Blood test in the morning — Testosterone is highest early in the day (before 11am)
- Fasting may be required — Food can affect results
- Two tests needed — One low result isn't enough; it needs confirming
- Other hormones checked — LH, FSH, prolactin to find the cause
Normal Testosterone Levels
Guide values GPs often use:
- Typical range: usually above 12 nmol/L (some guidelines use 10–12 nmol/L)
- Borderline range: 8–12 nmol/L
- Low range: below 8 nmol/L
These cut-offs are not absolute — UK laboratories differ, and testosterone varies by time of day (highest in the morning). Your GP interprets the result alongside your symptoms, the timing of the sample, and other hormones.
Things That Lower Testosterone Results
These can give falsely low results:
- Being unwell
- Poor sleep the night before
- Testing in the afternoon
- Obesity
- Some medications
This is why testing is repeated and done properly.
Treatment
Testosterone replacement is generally only considered when a specialist has confirmed low testosterone on repeat morning samples, symptoms fit with deficiency, and reversible causes (such as obesity, poor sleep, or medications that suppress testosterone) have been addressed first.
Forms of Testosterone Replacement
- Gel (Testogel, Tostran) — Applied daily to skin. Most common.
- Injections — given at intervals decided by your specialist (often every few weeks for shorter-acting preparations, or every few months for longer-acting ones).
- Patches — Applied daily
- Implants — pellets inserted under the skin; the interval depends on the specific preparation and is decided by your specialist.
Before Starting TRT
Your doctor should:
- Check PSA (prostate-specific antigen)
- Assess prostate with digital rectal exam
- Check blood count (haemoglobin/haematocrit)
- Discuss fertility — TRT reduces sperm production
- Discuss risks and benefits
Monitoring on TRT
Regular follow-up includes:
- Testosterone levels
- PSA and prostate assessment
- Blood count (to check for polycythaemia)
- Symptom review
Risks of Testosterone Therapy
- Polycythaemia — Blood becomes too thick, increasing clot risk
- Prostate concerns — May stimulate prostate growth; contraindicated with prostate cancer
- Infertility — TRT suppresses sperm production
- Acne and oily skin
- Sleep apnoea worsening
- Cardiovascular risk — Uncertain; needs monitoring
What About "Low T" Clinics?
Many private "men's health" or "TRT" clinics have emerged. Be cautious:
- Some may prescribe testosterone without proper assessment
- They may use lower thresholds for "low" testosterone
- Ongoing monitoring may be inadequate
- It can be expensive
If you genuinely have testosterone deficiency, the NHS can provide treatment with proper monitoring.
Buying Testosterone Online
This is illegal and dangerous.
- It's a controlled substance in the UK
- Products may be fake or contaminated
- There's no monitoring for side effects
- Self-medicating can cause serious harm
Natural Ways to Support Testosterone
Before considering TRT, these lifestyle factors can help optimise testosterone:
- Lose weight — Obesity lowers testosterone; losing weight can raise it
- Exercise — Especially resistance training
- Sleep well — Poor sleep significantly lowers testosterone
- Reduce stress — Chronic stress increases cortisol, which lowers testosterone
- Limit alcohol — Excess alcohol reduces testosterone
- Eat well — Adequate protein, healthy fats, zinc, and vitamin D
These won't "cure" true hypogonadism, but they can help borderline levels and improve symptoms regardless of testosterone level.