Persistent fatigue, low libido and muscle loss are common — and commonly dismissed. Here is the complete testing pathway, what your results mean, and what private TRT treatment involves.
Low testosterone — medically known as male hypogonadism — is significantly underdiagnosed in the UK. Research suggests it affects 10–40% of men over 45, yet the majority are never tested and even fewer receive treatment. This is partly because the symptoms — fatigue, reduced libido, mood changes, weight gain — are non-specific and commonly attributed to ageing or lifestyle.
At Lambert Medical Practice, we see a large number of men who have spent years feeling below par before a hormone blood panel explains why. This guide walks you through the symptoms that should prompt testing, what the testing process involves, and what private treatment looks like.
No single symptom is diagnostic — these overlap with many other conditions including thyroid dysfunction, depression, sleep disorders, obstructive sleep apnoea, iron deficiency and chronic fatigue. This is why blood testing is essential rather than optional.
Testosterone is not just one test — a thorough hormone panel is needed to diagnose the cause of low testosterone and assess whether treatment is appropriate. The key tests are:
| Test | What It Measures | Why It Matters |
|---|---|---|
| Total testosterone (morning) | Total circulating testosterone | Primary diagnostic marker. Must be measured before 10am (peak levels) |
| SHBG (sex hormone binding globulin) | Protein that binds testosterone | Needed to calculate free testosterone — the fraction available to cells |
| Free testosterone (calculated) | Unbound, active testosterone | Some men have low free T despite normal total T — SHBG explains why |
| LH (luteinising hormone) | Pituitary signal to produce testosterone | High LH = primary hypogonadism (testicular problem); Low LH = secondary (pituitary/hypothalamus) |
| FSH | Pituitary signal for sperm production | Guides fertility implications of low testosterone |
| Prolactin | Hormone from pituitary gland | Elevated prolactin can suppress testosterone — may indicate pituitary adenoma |
| Oestradiol (E2) | Oestrogen level | Elevated E2 (often in obesity) suppresses testosterone; monitored on TRT |
| PSA | Prostate-specific antigen | Baseline before TRT; elevation is a contraindication to treatment |
| Full blood count | Red blood cell parameters | Baseline haematocrit; TRT raises haematocrit — requires monitoring |
| Thyroid function (TSH) | Thyroid hormone | Hypothyroidism can mimic testosterone deficiency symptoms |
Important: Testosterone levels follow a diurnal rhythm — they are highest in the morning (7–10am) and fall by up to 30–50% by the afternoon. All testosterone measurements should be taken as a fasting morning sample. An afternoon result that looks "normal" may underestimate the problem.
The reference range for total testosterone varies slightly by laboratory, but the British Society for Sexual Medicine (BSSM) uses the following thresholds:
Two morning measurements below threshold are required before a diagnosis is made — single measurements can be misleading. Testosterone levels are also suppressed by acute illness, significant stress, obesity, alcohol and sleep deprivation, all of which should be considered when interpreting borderline results.
The NHS pathway for testosterone deficiency can be difficult to navigate. Common barriers include:
At Lambert Medical Practice, the entire pathway — initial consultation, full hormone panel, treatment discussion, and monitoring bloods — is managed in-house. Men who have been told their testosterone is "normal" on a single afternoon test, or who have been declined NHS treatment despite BSSM-qualifying blood results, regularly find that a thorough private assessment changes their situation.
Testosterone replacement therapy aims to restore testosterone to the mid-normal physiological range (typically 15–30 nmol/L on treatment). The initial consultation at Lambert Medical includes a thorough clinical and symptom assessment, review of your hormone panel, and a discussion of treatment options.
Treatment is a long-term commitment — testosterone levels fall when TRT is stopped, and symptoms return. This is why the decision to start should be made carefully, with realistic expectations about benefits and the need for ongoing monitoring.
Monitoring bloods — including testosterone, haematocrit, PSA, and LH/FSH — are arranged at 3 and 6 months after starting treatment, then annually once stable. These are essential for safe management and are included in the ongoing care pathway at Lambert Medical.
Morning hormone blood panel, full clinical assessment, and clear advice on whether TRT is appropriate for you. No NHS referral needed. Serving Surbiton, Kingston, Wimbledon and Surrey.
Also at Lambert Medical: Men's health / TRT service page · Blood tests Surbiton · 12 signs of low testosterone in men