MEN'S HEALTH
Erectile Dysfunction Blood Test UK: The Biomarkers That Reveal What's Actually Going On
Erectile dysfunction affects roughly one in five men over 40 in the UK — around 4.3 million men at any given time, according to NHS estimates. Most will never get a blood test. They'll get a prescription for sildenafil and a conversation that lasts about ninety seconds.
That's a problem, because ED is often the first visible symptom of something else. Cardiovascular disease, type 2 diabetes, thyroid dysfunction, and hormonal decline all present as erection problems years before other symptoms appear. A 2005 study in JAMA found that men with ED had a 45% higher risk of a cardiovascular event within ten years. The blood test isn't just about erections. It's a window into your vascular health.
This guide covers the ten biomarkers most likely to explain erectile dysfunction, what your GP will and won't test, the NHS vs optimal ranges, five common result patterns, and what to do with the numbers.
Medical review: Pending — awaiting medical reviewer approval. All claims in this guide link to NHS, NICE, BMJ, or PubMed sources.
Erectile dysfunction as an early-warning signal
The arteries supplying the penis are 1–2mm in diameter — roughly a third of the size of the coronary arteries that feed the heart. When atherosclerosis begins narrowing blood vessels, the smallest arteries are affected first. That is why ED often appears three to five years before a heart attack or stroke. The British Heart Foundation explicitly describes ED as a cardiovascular risk marker.
Beyond the vascular pathway, hormonal decline (testosterone drops roughly 1–2% per year after 30), thyroid imbalance, insulin resistance, and chronic inflammation all independently affect erectile function. A comprehensive blood panel doesn't just explain the symptom — it maps the underlying terrain.
The NICE guideline CG35 (Erectile dysfunction, 2024 update) recommends that all men presenting with ED should be assessed for cardiovascular risk factors, including fasting glucose or HbA1c, and a lipid profile. Most GPs stop there. The biomarkers below go further.
What your GP will (and won't) test
Under NICE CG35, a GP should request a fasting glucose or HbA1c, a lipid profile, and morning testosterone (if hormonal cause is suspected). In practice, many GP visits for ED skip blood tests entirely and move straight to a PDE5 inhibitor prescription.
The following markers are not part of standard NHS ED investigation but have strong evidence linking them to erectile function:
- •SHBG — determines how much testosterone is actually available to tissues
- •Free testosterone (calculated) — total T can be “normal” while free T is low
- •Prolactin — elevated prolactin directly suppresses libido and erectile function
- •TSH, fT4 — both hyper- and hypothyroidism cause ED through different mechanisms
- •hs-CRP — a marker of vascular inflammation that predicts endothelial dysfunction
- •Vitamin D — deficiency is independently associated with ED severity in multiple studies
The 10 biomarkers that matter for erectile dysfunction
These ten markers cover the three main physiological pathways behind ED: hormonal, vascular, and metabolic. Not every man needs all ten — but testing across all three pathways is how you avoid the tunnel vision of testing testosterone alone.
| Biomarker | Pathway | Why it matters for ED | Source |
|---|---|---|---|
| Total testosterone | Hormonal | Primary male sex hormone. Low T is the most common hormonal cause of ED. | NICE CG35 |
| SHBG | Hormonal | Binds testosterone. High SHBG = less free T reaching tissues, even with “normal” total T. | JCEM 2014 |
| Prolactin | Hormonal | Elevated prolactin suppresses GnRH, reducing testosterone and libido. SSRIs are a common cause. | Buvat 2003 |
| TSH | Hormonal | Hypothyroidism causes ED in up to 60% of affected men. Hyperthyroidism causes premature ejaculation. | Carani 2005 |
| HbA1c | Metabolic | Diabetes causes ED through nerve damage and small vessel disease. HbA1c >42 mmol/mol flags pre-diabetes. | NICE NG28 |
| Lipid profile | Vascular | High LDL and low HDL accelerate atherosclerosis in penile arteries. ApoB is the strongest predictor. | NICE CG181 |
| hs-CRP | Vascular | Chronic low-grade inflammation damages the endothelium. hs-CRP >3.0 mg/L correlates with ED severity. | Thompson 2005 |
| Fasting glucose | Metabolic | Insulin resistance damages nitric oxide pathways essential for erection. Complements HbA1c. | Bacon 2006 |
| Vitamin D | Vascular | Deficiency (<50 nmol/L) is associated with 30% higher ED risk. Vitamin D supports endothelial nitric oxide production. | Farag 2016 |
| Cortisol | Hormonal | Chronic stress elevates cortisol, which suppresses testosterone production and impairs vascular relaxation. | Corona 2012 |
NHS reference ranges vs optimal ranges for erectile health
NHS “normal” ranges are designed to flag disease, not to identify when your body is functioning below its potential. The optimal ranges below are based on published evidence linking specific thresholds to erectile function and cardiovascular risk.
| Biomarker | NHS range | Optimal for ED | Why |
|---|---|---|---|
| Total testosterone | 8–29 nmol/L | >15 nmol/L | BSSM guidelines define <8 as deficient, 8–12 as borderline. Symptoms improve above 15. |
| SHBG | 15–55 nmol/L | 20–40 nmol/L | Very high SHBG (>55) leaves too little free T. Very low (<15) can indicate insulin resistance. |
| Prolactin | <350 mU/L | <250 mU/L | Prolactin 250–350 can impair libido even within NHS range. Above 1000 warrants MRI. |
| TSH | 0.27–4.2 mIU/L | 0.5–2.5 mIU/L | TSH >2.5 may indicate subclinical hypothyroidism, linked to ED and fatigue. |
| HbA1c | <42 mmol/mol | <36 mmol/mol | HbA1c 36–42 is pre-diabetic. Insulin resistance impairs NO pathways at this level. |
| LDL cholesterol | <3.0 mmol/L | <2.5 mmol/L | Lower LDL reduces atherosclerotic burden. ESC/EAS 2019 recommend <2.6 for moderate CVD risk. |
| hs-CRP | <5.0 mg/L | <1.0 mg/L | hs-CRP 1–3 indicates intermediate cardiovascular risk. Below 1 is the target for endothelial health. |
| Vitamin D | >25 nmol/L | 75–125 nmol/L | NHS threshold prevents rickets. Levels 75+ support vascular endothelial function and testosterone synthesis. |
| Cortisol (morning) | 140–690 nmol/L | 250–500 nmol/L | Very high cortisol suppresses GnRH and testosterone. Very low may indicate adrenal insufficiency. |
| Fasting glucose | 3.5–5.5 mmol/L | 4.0–5.0 mmol/L | Fasting glucose 5.0–5.5 is impaired fasting glycaemia. Nitric oxide production drops. |
NICE CG35 recommended investigations for erectile dysfunction
NICE CG35 (updated 2024) recommends that men presenting with ED should receive:
| Investigation | Purpose | Included in Helvy panels? |
|---|---|---|
| HbA1c or fasting glucose | Screen for diabetes / pre-diabetes | Essential, Performance, Heart |
| Lipid profile | Cardiovascular risk assessment | Essential, Performance, Heart |
| Morning testosterone | Hypogonadism screening (if suspected) | Hormone Male, Performance |
| Blood pressure | Cardiovascular risk factor | Not a blood test — measured at home or GP |
| Thyroid function | If other symptoms suggest thyroid disease | Essential, Performance |
Helvy's Performance panel (£149) covers every blood-based investigation NICE recommends, plus SHBG, cortisol, DHEA-S, and hs-CRP — markers that add hormonal and inflammatory context the standard GP workup misses.
5 common ED blood test result patterns
Most men with ED don't have a single abnormal marker. They have a pattern — a cluster of related results that points to the dominant mechanism. These are the five we see most often in the published literature.
1. Low testosterone, high SHBG (“hidden hypogonadism”)
Total testosterone comes back at 12–15 nmol/L — technically within NHS range. But SHBG is 55+ nmol/L, so calculated free testosterone is well below the threshold. Symptoms: low libido, morning erections gone, fatigue, reduced muscle mass. Often seen in men over 45, or men on medications that raise SHBG (anticonvulsants, some antidepressants). Your GP may not test SHBG or calculate free T.
What to discuss with your GP: BSSM guidelines recommend assessment based on free testosterone, not total alone. If free T is low with symptoms, testosterone replacement therapy (TRT) may be appropriate. NICE CG35 supports referral to endocrinology.
2. Pre-diabetic / insulin resistant
HbA1c is 38–42 mmol/mol (pre-diabetic range). Fasting glucose is 5.5–6.0 mmol/L. LDL may be elevated. Testosterone is often low-normal because insulin resistance suppresses SHBG and alters the HPG axis. This is the most common metabolic pattern underlying ED in men under 50, especially those carrying abdominal weight.
What to discuss with your GP: The NHS Diabetes Prevention Programme (NICE NG28) is designed for exactly this situation. Structured lifestyle intervention reduces progression to type 2 diabetes by 58%.
3. Vascular / cardiovascular
LDL >3.5 mmol/L, hs-CRP >2.0 mg/L, possibly elevated ApoB or Lp(a). Testosterone is normal. The ED is driven by endothelial dysfunction — the lining of the blood vessels can't produce enough nitric oxide to relax the smooth muscle in the corpora cavernosa. This pattern carries the highest cardiovascular risk.
What to discuss with your GP: QRISK3 cardiovascular risk assessment. If 10-year risk is >10%, statin therapy per NICE CG181. Lifestyle: Mediterranean diet, 150 min/week moderate exercise, smoking cessation.
4. Thyroid-driven
TSH >4.0 mIU/L with or without low fT4. Hypothyroidism causes ED through multiple mechanisms: reduced NO synthesis, altered SHBG metabolism, fatigue, and weight gain. A 2005 study by Carani et al. found that correcting thyroid dysfunction resolved ED in 60% of men without any other intervention.
What to discuss with your GP: Thyroid function test with fT3 and fT4 (not just TSH). If confirmed hypothyroidism, levothyroxine per NICE NG145.
5. Stress / cortisol-dominant
Morning cortisol >550 nmol/L, testosterone on the lower end of normal, disrupted sleep, anxiety. Chronic stress activates the HPA axis, which directly competes with the HPG axis (testosterone production). Cortisol also impairs endothelial function independently. This pattern is common in high-pressure professionals aged 30–50.
What to discuss with your GP: Cortisol is best interpreted alongside DHEA-S (the anti-cortisol buffer). Referral for CBT, sleep hygiene assessment, or stress management. Ashwagandha has moderate evidence for cortisol reduction (Chandrasekhar 2012).
Hormonal causes: testosterone, prolactin, thyroid
Roughly 20–40% of ED cases have a hormonal component, according to a 2012 meta-analysis by Corona et al. in the Journal of Sexual Medicine. The three most common hormonal mechanisms:
Testosterone deficiency. The British Society for Sexual Medicine (BSSM) defines testosterone deficiency as total T <8 nmol/L (definite) or 8–12 nmol/L (borderline, interpret with symptoms and free T). But research consistently shows that erectile function and libido improve when total T is above 15 nmol/L. A man with a total T of 10 nmol/L is “within range” but likely symptomatic.
Hyperprolactinaemia. Prolactin above 350 mU/L suppresses GnRH, which reduces testosterone and directly impairs libido. Causes include pituitary adenoma (rare but important to exclude), medications (SSRIs, antipsychotics, domperidone), stress, and hypothyroidism. Prolactin above 1,000 mU/L warrants a pituitary MRI.
Thyroid dysfunction. Both hypo- and hyperthyroidism affect erectile function. Hypothyroidism causes ED through fatigue, weight gain, and reduced NO synthesis. Hyperthyroidism more commonly causes premature ejaculation. Treatment of the underlying thyroid condition resolves ED in a majority of cases without further intervention.
Vascular and metabolic causes: lipids, glucose, inflammation
The majority of ED cases in men over 50 are vascular in origin. Erection requires a large and rapid increase in blood flow to the corpora cavernosa, mediated by nitric oxide (NO) from the endothelium. Anything that damages the endothelium — high LDL, chronic inflammation, insulin resistance, smoking — impairs this mechanism.
The Thompson 2005 study in JAMA followed 9,457 men and found that those with ED had a 45% increased risk of cardiovascular events. A 2013 meta-analysis confirmed that ED precedes cardiovascular disease by a median of 3–5 years.
The clinical message: if your lipids, HbA1c, or hs-CRP are elevated and you have ED, the ED is your body telling you something about your arteries. Treating only the ED with PDE5 inhibitors without addressing the underlying vascular risk is treating the symptom while ignoring the disease.
GP vs Helvy: what each covers
| Marker | NHS GP | Helvy Performance | Helvy Hormone Male |
|---|---|---|---|
| Total testosterone | Sometimes | Yes | Yes |
| Free testosterone | Rarely | Calculated | Yes |
| SHBG | Rarely | Yes | Yes |
| Prolactin | Rarely | No | Yes |
| TSH | Sometimes | Yes | No |
| HbA1c | Yes | Yes | No |
| Lipid profile | Yes | Yes | No |
| hs-CRP | Rarely | Yes | No |
| Cortisol | Rarely | Yes | Yes |
| Vitamin D | Rarely | Yes | No |
| DHEA-S | No | Yes | Yes |
The Helvy Performance panel (£149) gives the broadest ED coverage — cardiovascular, metabolic, hormonal, and inflammatory markers in one test. If hormones are the primary concern, the Hormone Male panel (£119) goes deeper on testosterone, prolactin, and DHEA-S.
What to do with your results
Blood test results are a conversation starter, not a diagnosis. Here is how to use them:
- 1.Identify the dominant pattern. Which of the five patterns above best describes your results? Most men have one primary mechanism driving their ED, even if other markers are slightly off.
- 2.Print your results and take them to your GP. Private blood test results from a UKAS-accredited lab carry the same clinical weight as NHS-ordered tests. Your GP can use them to inform referrals.
- 3.Ask for the next investigation. If testosterone is low, ask for LH and FSH to determine whether the cause is testicular (primary) or pituitary (secondary). If lipids are elevated, ask for a QRISK3 assessment.
- 4.Start with lifestyle before medication. The evidence-based interventions below have meaningful effect sizes and zero side effects. Medication works alongside lifestyle, not instead of it.
When to retest
| Scenario | Retest interval |
|---|---|
| Baseline ED investigation | First test now |
| After starting TRT | 6–8 weeks, then 3-monthly for the first year (BSSM) |
| After lifestyle intervention (diet, exercise) | 12 weeks (allows HbA1c + lipids to reflect changes) |
| After starting thyroid medication | 6–8 weeks (NICE NG145) |
| Annual monitoring (stable, no concerns) | Every 12 months |
Evidence-based interventions for erectile dysfunction
These interventions have published evidence in peer-reviewed journals. They address root causes — not just symptoms. Discuss any new supplement or lifestyle change with your GP, especially if you take medication.
Mediterranean diet
A 2006 Esposito et al. study in JAMA found that a Mediterranean diet improved erectile function in 1 in 3 men with metabolic syndrome over two years. Mechanism: reduced inflammation, improved endothelial function, better insulin sensitivity.
Aerobic exercise (150 min/week)
A 2018 meta-analysis in Sexual Medicine Reviews found that aerobic exercise significantly improved erectile function with an effect size comparable to PDE5 inhibitors. Zone 2 cardio (conversational pace) for 30 min, five days a week.
Vitamin D supplementation
If your level is below 75 nmol/L, supplementing with 1,000–2,000 IU vitamin D3 daily supports endothelial NO production and testosterone synthesis. NHS recommends 400 IU minimum from October to March; higher doses for deficiency.
Weight loss (if BMI >30)
A 2004 Esposito et al. trial in JAMA found that 10% body weight loss restored erectile function in a third of obese men. Adipose tissue converts testosterone to oestradiol via aromatase, and increases insulin resistance.
Omega-3 fatty acids
EPA and DHA support endothelial function and reduce inflammation. A dose of 2–4g combined EPA/DHA daily has the strongest evidence for cardiovascular benefit (BHF). Particularly relevant in the vascular/inflammatory ED pattern.
Sleep optimisation (7–9 hours)
Testosterone is produced primarily during REM sleep. A 2011 JAMA study found that one week of restricted sleep (5 hours/night) reduced testosterone by 10–15% in young healthy men. Poor sleep also elevates cortisol, compounding the hormonal impact.
Frequently asked questions
Can a blood test actually diagnose erectile dysfunction?
No. ED is diagnosed clinically, based on your symptoms and history. A blood test identifies the underlying causes — hormonal, vascular, or metabolic — so treatment targets the root problem rather than just masking the symptom.
Should I get a blood test before taking Viagra or sildenafil?
Ideally, yes. PDE5 inhibitors treat the symptom but not the cause. If your ED is driven by low testosterone, pre-diabetes, or thyroid dysfunction, sildenafil may work temporarily while the underlying condition gets worse. NICE CG35 recommends cardiovascular risk assessment for all men with ED.
What time of day should I get my blood taken for ED tests?
Before 10am, fasting. Testosterone peaks between 7am and 10am and drops by 20–30% by afternoon. A blood test taken at 3pm may show falsely low testosterone. HbA1c and lipids are more accurate fasting.
My GP says my testosterone is 'normal' at 11 nmol/L. Should I push for more?
11 nmol/L is in the borderline zone (8–12 nmol/L per BSSM guidelines). If you have symptoms — low libido, fatigue, loss of morning erections, reduced muscle — ask your GP to test SHBG and calculate free testosterone. A free T result below the reference range, combined with symptoms, supports further investigation.
Can lifestyle changes really fix erectile dysfunction?
For many men, yes. The evidence is strongest for aerobic exercise (effect size comparable to PDE5 inhibitors in published meta-analyses), Mediterranean diet, weight loss, and sleep. These interventions address the vascular and metabolic root causes. Results typically appear over 8–12 weeks.
How much does a private ED blood test cost in the UK?
A comprehensive hormone and cardiovascular panel typically costs £100–200. Helvy's Performance panel (£149) covers testosterone, SHBG, cortisol, DHEA-S, thyroid, HbA1c, lipids, hs-CRP, and vitamin D — all the markers discussed in this guide. The Hormone Male panel (£119) focuses on the hormonal pathway specifically.
Is erectile dysfunction always a sign of heart disease?
Not always, but the association is strong enough that the British Heart Foundation classifies ED as a cardiovascular risk marker. A 2005 JAMA study found a 45% increased risk of cardiovascular events in men with ED. If your lipids or hs-CRP are elevated alongside ED, discuss cardiovascular risk with your GP.
A blood test won't fix ED overnight. But it will tell you whether your hormones, arteries, or metabolism are the root cause — and that changes everything about what you do next.
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