Why Testosterone Testing Matters
Low testosterone (hypogonadism) is significantly underdiagnosed in the UK. Many men spend years attributing fatigue, low libido, weight gain, and mood changes to stress or ageing, when the underlying cause is a hormonal deficiency that is both measurable and treatable.
The challenge is that symptoms of low testosterone overlap with many other conditions — thyroid problems, sleep apnoea, iron deficiency, depression — which is why a targeted blood test panel, not just a single testosterone number, is the right starting point.
Which Blood Tests Should You Request?
A proper testosterone assessment requires more than just a "testosterone test." Here's what a comprehensive panel should include:
| Test | Why It's Needed |
|---|---|
| Total testosterone | The standard first measurement. Reflects the total amount in the blood but includes bound (inactive) testosterone. |
| SHBG (sex hormone binding globulin) | Binds testosterone and makes it unavailable to tissues. Essential for calculating free testosterone. |
| Free testosterone (calculated) | The biologically active fraction. Men can have normal total testosterone but low free testosterone and still have symptoms. |
| LH (luteinising hormone) | Identifies whether low testosterone is caused by the pituitary gland (secondary hypogonadism) or the testes (primary). |
| FSH (follicle stimulating hormone) | Provides further information about testicular function. |
| Prolactin | Elevated prolactin can suppress testosterone. A pituitary tumour (prolactinoma) is an important cause to rule out. |
| Thyroid function (TSH, fT4) | Thyroid problems cause identical symptoms to low testosterone and must be excluded. |
| Full blood count | Checks for anaemia (which causes fatigue). Also provides a haematocrit baseline before TRT if initiated. |
| PSA (if over 40) | Required before starting TRT to establish a baseline. Elevated PSA may indicate prostate disease and would need investigation before TRT is considered. |
When Should You Test?
Testosterone levels follow a circadian rhythm — they are highest in the early morning and lowest in the evening. For accurate results:
- Time your blood draw between 7am and 10am — afternoon results can underestimate true levels by 20–30%
- Fast overnight — eat nothing after 10pm and drink only water before the test
- Avoid strenuous exercise the night before — intense exercise transiently affects hormone levels
- Avoid alcohol for 48 hours beforehand — alcohol suppresses testosterone
- Confirm on a second sample — if the first result is low, UK guidelines recommend confirming on a second morning sample before making a diagnosis
How to Read Your Results
UK laboratory reference ranges vary between providers, but broadly:
>12 nmol/L
8–12 nmol/L
<8 nmol/L
Important caveats: these are population reference ranges, not therapeutic targets. Many men with total testosterone in the 8–12 nmol/L range have clear symptoms and benefit from treatment. The key number is often calculated free testosterone — the European Male Ageing Study defines deficiency as free testosterone below 0.225 nmol/L.
The "normal range" problem
Lab reference ranges are derived from population averages, not from symptom thresholds. A 35-year-old with total testosterone of 10 nmol/L is technically "normal" by lab standards but is in the bottom quartile for his age — equivalent to an 80-year-old's average. Many clinicians now use a symptom-driven approach rather than relying solely on the number.
What If My Testosterone Is Low?
A confirmed low testosterone result, alongside symptoms, qualifies for treatment consideration. Options include:
- Testosterone Replacement Therapy (TRT) — the most effective treatment for primary and secondary hypogonadism. Available as gels, injections, or patches. Our TRT clinic in Surbiton offers a full assessment, blood testing, and ongoing monitoring from £132/month.
- Lifestyle optimisation first — if testosterone is borderline, a structured programme of sleep, strength training, body fat reduction, and stress management can raise levels meaningfully before pharmacological treatment is considered
- Investigation of secondary causes — elevated prolactin, pituitary lesions, or other reversible causes need addressing before TRT is started
Can My NHS GP Test My Testosterone?
Yes — but NHS GPs typically only test total testosterone, and only if symptoms are clearly consistent with hypogonadism. SHBG and free testosterone are often not included. Waiting times for an NHS appointment and then a follow-up to discuss results can mean delays of several weeks.
Private testing at Lambert Medical Practice provides a same-morning blood test with GP-reviewed results within 24 hours, including a full panel (total testosterone, SHBG, free testosterone, LH, FSH, prolactin, thyroid, PSA, and FBC).