Testosterone Blood Test UK: What's Tested, How to Read Your Results & What to Do Next

1. Why Test Testosterone?

Testosterone is the primary androgen in both men and women. In men, it governs muscle mass, bone density, red blood cell production, fat distribution, libido, mood and cognitive function. In women, it plays a smaller but important role in energy, libido, bone health and muscle maintenance.

The British Society for Sexual Medicine (BSSM) estimates that up to 12% of men aged 40–79 have biochemical testosterone deficiency, yet fewer than 5% are ever diagnosed. The gap is driven by three problems: GPs rarely test proactively, NHS reference ranges are too wide, and total testosterone alone misses cases where SHBG is elevated and free testosterone is genuinely low.

Testing is valuable if you experience persistent fatigue, reduced libido, erectile dysfunction, difficulty building muscle despite training, increased body fat (especially abdominal), low mood, brain fog, or poor recovery from exercise. These symptoms overlap with many other conditions — a blood test is the only objective way to confirm whether testosterone is a contributing factor.

2. What a Full Testosterone Panel Includes

A single total testosterone number tells you surprisingly little. A comprehensive panel includes several markers that together reveal not just how much testosterone you produce, but how much your body can actually use.

3. NHS Reference Ranges vs Optimal

NHS reference ranges for testosterone are derived from population studies that include men with chronic illness, obesity and age-related decline. The result is an extraordinarily wide range. The BSSM and Endocrine Society (JCEM 2018) both recommend diagnosis of testosterone deficiency below specific thresholds — but the grey zone between “deficient” and “optimal” is where most symptomatic men sit.

Reference ranges vary by laboratory. NHS ranges shown are typical for adult men using LC-MS/MS assay. The BSSM threshold of 12 nmol/L is the level below which treatment should be considered in symptomatic men.

4. When and How to Test (Timing Matters)

Testosterone follows a circadian rhythm: levels peak between 7–10 am and can drop by 20–40% by late afternoon. The BSSM and Endocrine Society both recommend measuring testosterone in a fasted, morning sample before 10 am. An afternoon blood draw can make a man with normal testosterone appear deficient.

Other factors that transiently suppress testosterone and should be avoided before testing:

• •Alcohol within 24 hours (suppresses LH pulsatility)
• •Intense exercise the day before (acute cortisol spike lowers testosterone)
• •Poor sleep the night before (even one night of 4 hours reduces morning testosterone by 10–15%)
• •Acute illness or caloric restriction (the hypothalamus downregulates reproduction under stress)
• •Opioid medications (potent suppressors of the HPG axis)

The BSSM recommends two separate morning samples at least four weeks apart before diagnosing testosterone deficiency. A single low result can be caused by any of the transient factors above.

5. Low Testosterone: Causes and Symptoms

Male hypogonadism is classified into two types. The distinction matters because it determines both the cause and the treatment approach.

The European Male Ageing Study (EMAS) followed 3,369 men and found that only three symptoms were consistently associated with confirmed low testosterone: poor morning erections, low sexual desire, and erectile dysfunction. Other commonly attributed symptoms (fatigue, low mood, reduced muscle mass) were equally common in men with normal testosterone — reinforcing why a blood test is essential rather than diagnosing by symptoms alone.

For a detailed look at symptoms and their association with testosterone levels, see our guide on low testosterone symptoms in men.

6. High Testosterone and What It Means

Naturally high testosterone within the reference range is not a health concern. Supra-physiological levels — testosterone well above the upper limit — are almost always caused by exogenous testosterone or anabolic steroids.

In men, persistently elevated testosterone above 30–35 nmol/L warrants investigation for:

• •Exogenous androgen use (including TRT at excessive doses)
• •Congenital adrenal hyperplasia (21-hydroxylase deficiency)
• •Androgen-secreting adrenal or testicular tumour (rare but must be excluded)
• •HCG-secreting tumour (very rare)

In women, elevated testosterone is a hallmark of PCOS, congenital adrenal hyperplasia, or androgen-secreting tumours. Symptoms include acne, hirsutism, scalp hair thinning, irregular periods and difficulty conceiving.

7. SHBG: Why Free Testosterone Matters More Than Total

This is the single most misunderstood aspect of testosterone testing. Two men with identical total testosterone of 15 nmol/L can have completely different symptom profiles if one has an SHBG of 20 nmol/L (plenty of free testosterone) and the other has an SHBG of 60 nmol/L (very little free testosterone).

The NHS rarely tests SHBG or calculates free testosterone. This means a significant proportion of symptomatic men are told their testosterone is “fine” when their bioavailable fraction is genuinely low.

Common causes of high SHBG (which lowers free testosterone):

• •Ageing (SHBG rises approximately 1.6% per year after age 40)
• •Hyperthyroidism (excess thyroid hormone stimulates SHBG production)
• •Liver disease (the liver produces SHBG)
• •Anticonvulsant medications (carbamazepine, phenytoin)
• •Oestrogen therapy or environmental oestrogen exposure

Common causes of low SHBG (which increases free testosterone): obesity, insulin resistance, type 2 diabetes, hypothyroidism, anabolic steroid use, and nephrotic syndrome.

8. GP Testosterone Test vs Helvy

The fundamental difference is scope. A GP will typically test total testosterone only — and only if symptoms are severe enough to warrant investigation. The Helvy Hormone (Male) panel tests the full axis in one draw.

Your GP is always the right first step if you suspect a pituitary problem, have severely low mood, or need a TRT referral. Helvy is designed for proactive screening and early detection.

9. Six Common Result Patterns

Testosterone results rarely exist in isolation. The pattern across multiple markers is what tells the clinical story.

10. Evidence-Based Ways to Raise Testosterone Naturally

Before considering pharmaceutical intervention, the evidence supports several lifestyle changes that can meaningfully raise testosterone. These are not marginal — in overweight, sedentary or sleep-deprived men, the gains can rival TRT.

The cumulative effect of addressing all of these factors simultaneously can be substantial. A man who is overweight, sleeping poorly, vitamin D deficient, zinc depleted and drinking heavily could see a 10+ nmol/L increase in total testosterone over 6–12 months without any pharmaceutical intervention.

11. When to Consider TRT (and When Not To)

Testosterone replacement therapy is appropriate when a man has confirmed biochemical testosterone deficiency on two morning samples AND persistent symptoms AND reversible causes have been addressed. The BSSM guidelines recommend treatment when total testosterone is persistently below 8 nmol/L, or between 8–12 nmol/L with symptoms and low free testosterone.

TRT should not be started when:

• •Reversible causes haven't been addressed (obesity, sleep apnoea, opioids, alcohol)
• •Fertility is desired — TRT suppresses sperm production and can cause infertility
• •Prolactin is elevated — investigate and treat the cause first
• •PSA is elevated or prostate cancer is suspected — urology review first
• •Haematocrit is already high (>0.54) — TRT increases red blood cell production
• •Severe untreated sleep apnoea — TRT can worsen obstructive sleep apnoea

In the UK, TRT is available on the NHS via endocrinology referral. The most common form is testosterone undecanoate injection (Nebido) every 10–14 weeks, or testosterone gel (Testogel, Tostran) applied daily. Men on TRT require regular monitoring of haematocrit, PSA, liver function and lipids. For a deeper look at testosterone decline with age, see our testosterone levels by age guide.

12. Testosterone Testing in Women

Testosterone is not just a male hormone. Women produce testosterone in the ovaries and adrenal glands, and it plays a role in energy, libido, bone density, and mood. Female testosterone levels are approximately 10–20 times lower than male levels.

Testosterone testing in women is primarily indicated for:

• •Investigation of PCOS (elevated testosterone is one of the three Rotterdam criteria)
• •Hirsutism or acne that doesn't respond to standard treatment
• •Female-pattern hair loss (androgenetic alopecia)
• •Low libido, especially after menopause or oophorectomy
• •Virilisation symptoms (deepening voice, clitoromegaly) — urgent investigation required

The Helvy Hormone (Female) panel includes testosterone, SHBG and the free androgen index (FAI). For PCOS-specific investigation, see our PCOS blood test guide.

13. When to See Your GP Urgently

Most testosterone concerns are non-urgent and suited to proactive monitoring. However, certain findings require prompt medical attention:

• •Total testosterone below 5 nmol/L — severe deficiency requiring urgent evaluation
• •Prolactin above 1,000 mIU/L — investigate for pituitary adenoma
• •Sudden onset of erectile dysfunction with visual field changes — pituitary mass must be excluded
• •Rapid virilisation in women — investigate for androgen-secreting tumour
• •Gynaecomastia (breast tissue growth) in men — evaluate testosterone:oestradiol ratio
• •New testicular lump or asymmetry discovered alongside abnormal hormones

If any of these apply to you, do not wait for a private blood test. Contact your GP or call 111 for same-day guidance.

14. Frequently Asked Questions