ERECTILE DYSFUNCTION (ED) BLOOD TEST

This blood test assesses key hormonal, metabolic, and cardiovascular markers that may contribute to erectile dysfunction (ED). It includes testosterone (free and total), prolactin, sex hormone-binding globulin (SHBG), thyroid hormones, cholesterol profile, and HbA1c. The test is suitable for men experiencing persistent or unexplained erectile issues and seeking a medically grounded assessment of potential underlying causes.

Understanding the biological context of erectile dysfunction is essential for effective care. Without testing, it is difficult to distinguish between psychological, lifestyle-related, and medical causes. This can delay treatment or lead to interventions that do not address the underlying issue.

This test provides a clear snapshot of several key systems known to affect erectile function. By identifying low testosterone, raised prolactin, impaired thyroid function, or early metabolic disease, it allows you and your clinician to explore evidence-based treatment options. In some cases, simple lifestyle changes or medical treatment can restore normal function. In others, further investigations may be needed.

The test also serves a broader purpose. It can highlight areas of health that may not yet have caused symptoms, such as early diabetes or cardiovascular risk. Erectile dysfunction, particularly when persistent or unexplained, can be a sentinel sign of more widespread vascular or endocrine disease. Early detection improves long-term health outcomes.

Even when no clear physiological cause is found, the reassurance provided by normal results can support a shift toward psychological or relationship-based approaches, where appropriate. In this way, the test plays a role in both diagnosis and exclusion, helping to focus care where it is most likely to be effective.

Whether you are beginning to experience symptoms, managing a known condition, or simply want to understand your health better, this test provides a solid clinical foundation for taking the next step.

Even if your blood tests are normal, you should see a doctor if you have any of the symptoms below because they may be a sign of serious underlying illness. 

• Progressive muscle weakness
• Unexplained weight loss
• Progressively severe symptoms of any kind

Hormone levels, particularly testosterone, follow a daily rhythm and are most reliably measured in the morning. For this reason, it is best to have your sample taken before 10 am.

Avoid strenuous exercise, heavy alcohol intake in the 24 hours before testing and don't do the test immediately after an acute illness. All of these can influence hormone levels.

If you are taking medications that affect hormone production or metabolism, such as steroids, antipsychotics, or thyroid medications, take these into account when interpreting the results.

If you are undergoing treatment for a known endocrine or metabolic condition, it is helpful to time the test at a consistent point in your treatment cycle to ensure comparability with previous results.

If you are taking biotin supplements, stop taking these 72 hours before the test.

If you are using testosterone gel supplements, do not take the finger prick test from the hand you use to apply the gel and sanitise the hands thoroughly. In general, if you are using gel supplements for hormones - come into a clinic for a venous sample, it will be much more predictable as the gels are very persistent on the skin and cross contamination happens frequently.

Why do you measure cholesterol for erectile dysfunction diagnosis?

This includes measurements of total cholesterol, LDL (low-density lipoprotein), HDL (high-density lipoprotein), and triglycerides. Atherosclerosis—the narrowing of blood vessels due to cholesterol deposits—can restrict blood flow to the penis and impair erection. ED can be an early sign of broader cardiovascular disease. Understanding lipid status provides insight into vascular health and future risk.

Together, these markers offer a rounded view of the hormonal, metabolic, and vascular contributors to erectile function. While the test is not diagnostic of ED in itself, it provides essential clinical information that can guide further evaluation or treatment.

Why measure HbA1c/blood sugar for ED?

HbA1c reflects average blood glucose levels over the past 8–12 weeks and is used to diagnose or monitor diabetes. Poor glucose control can damage blood vessels and nerves, both of which are essential for erectile function. Even in the absence of diagnosed diabetes, raised HbA1c can indicate insulin resistance and metabolic dysfunction. Erectile issues are sometimes an early indicator of undetected diabetes.

Can I take this test if I am using testosterone replacement therapy?

Yes, you can use this test to monitor your response to treatment.

Why is testosterone (free and total) measured for erectile dysfunction?

Testosterone is a key male hormone involved in sexual function, mood, and energy. Low levels may lead to reduced libido, difficulty achieving or maintaining erections, and other symptoms such as fatigue or low motivation. Both total and free testosterone are relevant, as only unbound testosterone is biologically active. By measuring testosterone levels, this test helps identify whether androgen deficiency could be contributing to ED.

Why is Prolactin and SHBG measured?

SHBG binds to testosterone and regulates its availability. When SHBG is elevated, it can reduce the proportion of free, active testosterone, even if total testosterone appears normal. This is particularly relevant in older men, where SHBG levels tend to increase with age. Measuring SHBG provides context to testosterone results and helps interpret whether androgen function is adequate.

Prolactin is a hormone produced by the pituitary gland. Elevated prolactin can suppress the hypothalamic-pituitary-gonadal axis, leading to lower testosterone and decreased libido. In some cases, high prolactin levels may be due to benign pituitary tumours or medications. It is less commonly measured than testosterone but plays a crucial role in the regulation of male reproductive hormones.