Blood Tests for Erectile Dysfunction in Australia

Why blood tests matter when you have ED

Erectile function depends on healthy blood vessels, nerves and hormones, so ED is often the earliest symptom of a vascular or metabolic condition that has not yet declared itself elsewhere.

An erection is a vascular event. It requires the endothelium — the inner lining of blood vessels — to release nitric oxide and allow the penile arteries to dilate and fill. Those arteries are narrow, in the range of one to two millimetres, compared with three to four millimetres for the coronary arteries. When endothelial function starts to decline, the smallest vessels show it first.

That anatomical detail has a clinical consequence worth taking seriously: in men with vasculogenic ED, symptoms commonly precede a cardiac event by three to five years. Australian general practice guidance treats new ED in a middle-aged man as a prompt to assess cardiovascular risk properly — blood pressure, lipids, glucose, smoking, weight — not simply as a sexual complaint.

The endocrine side matters too, though less often than people expect. Low testosterone contributes to reduced libido and can contribute to ED, but it is a less frequent single cause than vascular disease, diabetes, medicines and psychological factors. Raised prolactin is uncommon but important, because it is identifiable and reversible, and because it can indicate a pituitary lesion.

To be explicit about scope: this page is about which measurements are worth having. FORM is a pathology testing service. We do not prescribe, supply, or recommend any medicine, device or procedure for erectile dysfunction, and we are not an alternative to seeing a doctor. Take your results to your GP.

Which blood tests are worth running

The core panel is a morning testosterone with SHBG and LH, prolactin, HbA1c and a fasting lipid profile, with thyroid function, renal function and a full blood count added where the history suggests.

Testosterone and erectile dysfunction: what the relationship actually is

Low testosterone more consistently reduces libido than it causes erectile failure, and most men with ED have normal testosterone — which is precisely why measuring it is worthwhile rather than assumed.

The honest summary is that the link is real but weaker and more specific than the internet suggests. Testosterone supports libido, spontaneous and nocturnal erections, and nitric oxide signalling in penile tissue. Men with clearly low testosterone often report reduced desire first, with erectile difficulty following. But population studies consistently find that most men presenting with ED have testosterone within the reference range, and that vascular, metabolic, medicine-related and psychological factors account for far more cases.

There is also a shared-cause problem that is easy to misread. Obesity, type 2 diabetes, obstructive sleep apnoea and metabolic syndrome all lower testosterone and independently cause ED. Finding a modestly low testosterone in a man with a large waist and an HbA1c of 50 mmol/mol does not mean the testosterone caused the ED — both are downstream of the same metabolic picture, and Australian guidance is that the metabolic problem is addressed first.

Measurement discipline matters. Testosterone must be collected between 7am and 10am, because levels fall by 20 to 30 per cent through the day. A single low result is never sufficient: Endocrine Society of Australia guidance is that hypogonadism requires at least two low morning samples on separate days, with LH and FSH, before any diagnosis is made. Acute illness, poor sleep and recent heavy training all lower a single reading transiently.

The individual tests in an ED work-up

Each component of the panel has its own reference guide with Australian ranges and interpretation.

• Testosterone test — morning collection, total versus free, and why two samples are needed.
• Prolactin blood test — an uncommon but important and reversible contributor.
• HbA1c test — average glucose over two to three months, and what falsely raises or lowers it.
• LH and FSH blood test — localises a low testosterone to the testis or the pituitary.
• Thyroid function test — thyroid dysfunction in either direction affects sexual function.
• Full blood count — anaemia, and polycythaemia monitoring in men already on testosterone.
• Build your own Australian panel — assemble testosterone, prolactin, HbA1c and lipids in one collection.
• FORM Australian panels — the standard tiers already include testosterone, HbA1c and a full lipid profile.

HbA1c, lipids and the cardiovascular angle

HbA1c and a lipid profile are included not as an afterthought but because ED is a recognised early marker of endothelial dysfunction and undiagnosed diabetes.

Diabetes affects erectile function through two mechanisms simultaneously: it damages the small arteries and it damages the autonomic nerves that initiate the vascular response. ED appears earlier and is more severe in men with diabetes, and a meaningful proportion of men presenting with ED are found to have diabetes or prediabetes that nobody had looked for. HbA1c is a single non-fasting-tolerant test that reflects the previous two to three months of average glucose.

The lipid profile serves the same purpose from the other direction. Atherosclerosis is systemic, and the penile arteries are small enough to show it early. In Australia, lipid results are interpreted within an absolute cardiovascular risk calculation that also uses age, sex, blood pressure, smoking status and diabetes — a single cholesterol number in isolation means less than the calculated risk it feeds into.

Blood pressure is not a blood test but belongs in the same assessment, and it is worth having measured properly by your GP alongside these results. So does a conversation about sleep, because obstructive sleep apnoea is common, under-diagnosed, and lowers both testosterone and erectile function.

What can distort this panel

Collection time, fasting status, acute illness, medicines and supplements all move these results in ways that change interpretation.

• Testosterone collected after 10am reads 20–30% lower — an afternoon sample is not interpretable for hypogonadism.
• Acute illness, sleep deprivation, a heavy training block or a very low-energy diet all transiently lower testosterone.
• Prolactin rises with stress, exercise, a difficult venepuncture and several common medicines — sit quietly for 20 to 30 minutes first.
• Lipids are conventionally measured fasting; a non-fasting sample mainly raises triglycerides.
• HbA1c is falsely low with recent blood loss, haemolysis or shortened red cell survival, and falsely high in iron deficiency — see our HbA1c page for the full list.
• Many medicines contribute to ED independently, including some antihypertensives, antidepressants, antipsychotics, finasteride and opioids. Bring your full list to your GP rather than stopping anything.
• Alcohol, smoking and recreational drug use affect both the results and the symptom.
• High-dose biotin supplements interfere with immunoassays — stop 48–72 hours before testing.

Who should consider this panel

Any man with persistent erectile difficulty benefits from a baseline panel, and the case is stronger where risk factors or other symptoms are present.

Some situations need a doctor rather than a test first. Sudden-onset ED after a specific event, ED with pelvic or perineal pain, penile curvature or plaques, ED following pelvic surgery or radiotherapy, and ED with chest pain or breathlessness on exertion should be discussed with a GP promptly.

• Persistent erectile difficulty over more than a few months, particularly if it has developed gradually.
• ED with reduced libido, fatigue, loss of morning erections or reduced body hair — an endocrine pattern worth measuring.
• Any cardiovascular risk factor: raised blood pressure, smoking, central obesity, family history of early heart disease.
• Known or suspected diabetes or prediabetes, or symptoms such as thirst, frequent urination or unexplained weight change.
• Snoring, witnessed apnoeas or unrefreshing sleep — obstructive sleep apnoea affects both testosterone and erectile function.
• Before any medical consultation about ED, so the conversation starts with data rather than assumptions.

How ED blood testing works with FORM in Australia

You order the panel, we issue an Australian pathology request form, and you attend an accredited collection centre for one early-morning fasting draw.

• No referral from your own GP is required. Privately requested pathology is arranged under a request from a registered medical practitioner working with our accredited lab partner.
• Collection is a walk-in at Laverty (Healius) pathology centres Australia-wide (NATA / ISO 15189 accredited).
• Results are returned in Australian SI units with a written, plain-English explanation.
• FORM is a diagnostic testing service. We do not prescribe or supply medicines — take your results to your GP or a specialist.
• Australian ordering is currently pre-sale. Join the waitlist and we will email you when ordering opens.
• One visit covers the whole panel: fasted, between 7am and 10am, after a short seated rest for prolactin.
• Where testosterone comes back low, a second morning sample with LH and FSH is the standard confirmation step before anything is concluded.
• Results typically report within one to three business days, with each marker explained in context.
• We do not provide erectile dysfunction treatment of any kind, and we are not a men's clinic. Results are for you and your GP.