Blood Tests Recommended for Erectile Dysfunction
Morning serum total testosterone should be measured in all men presenting with erectile dysfunction, along with fasting glucose (or HbA1c) and a lipid profile as mandatory baseline testing. 1, 2
Mandatory Core Laboratory Tests
All men with erectile dysfunction require the following blood tests at initial evaluation:
Morning total testosterone level - This is the single most important hormonal test and should be obtained in all men with ED, particularly those who fail PDE5 inhibitor therapy. 1 The morning timing is critical due to diurnal variation in testosterone levels. 2 Testosterone deficiency is defined as total testosterone <300 ng/dL with accompanying symptoms. 1
Fasting glucose or HbA1c - Essential for screening diabetes, as ED is commonly the first presenting symptom of diabetes mellitus. 2, 3 This addresses both diagnosis and cardiovascular risk stratification, which directly impacts mortality. 1
Lipid profile (total cholesterol, HDL, LDL, triglycerides) - Required to assess cardiovascular risk factors, as ED is a sentinel marker for cardiovascular disease that typically presents 3 years before coronary symptoms. 1, 2, 3
Additional Testing Based on Clinical Context
If hypogonadism is suspected based on symptoms (decreased libido, loss of morning erections) or physical findings (testicular atrophy, muscle loss):
- Free testosterone or bioavailable testosterone is preferred over total testosterone alone 2
- If testosterone is confirmed low on repeat testing, measure LH, FSH, and prolactin to distinguish primary from secondary hypogonadism 4
If testosterone replacement therapy is being considered:
- Prostate-specific antigen (PSA) and digital rectal examination should be obtained as baseline measurements 2
Important Clinical Context
The rationale for this testing strategy is grounded in mortality and morbidity reduction. Low testosterone levels are associated with significantly increased all-cause mortality (hazard ratios ranging from 1.24 to 2.32) and cardiovascular mortality (hazard ratios up to 7.1) across multiple large prospective studies. 1 Additionally, 36% of men presenting with sexual dysfunction have hypogonadism, and testosterone deficiency can cause lack of response to PDE5 inhibitor therapy. 1
ED itself should be considered a cardiovascular risk marker until proven otherwise, particularly in men aged 30-60 years. 1 The presence of ED warrants cardiovascular risk assessment independent of traditional risk scores. 1
Common Pitfalls to Avoid
Do not measure testosterone at random times of day - Only morning samples (ideally 7-11 AM) are valid due to circadian rhythm. 2
Do not order extensive hormonal panels initially - A single morning testosterone measurement is adequate for initial screening; only pursue LH, FSH, and prolactin if testosterone is low on repeat testing. 4
Do not skip metabolic testing - Even if ED appears purely psychogenic based on history (preserved morning erections), fasting glucose and lipids remain mandatory as ED may be the first sign of systemic vascular disease. 3
Do not forget that "normal" testosterone assays vary - There are no universally accepted lower limits of normal, and assay methods differ between laboratories. 1 Clinical correlation with symptoms is essential.