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Testosterone testing explained
Short answer: Neither test is universally better. Early-morning total testosterone is generally the starting test when evaluating possible testosterone deficiency in men with erectile dysfunction. Free testosterone, interpreted with SHBG, can add useful context when total testosterone is borderline, symptoms and total testosterone do not match, or a condition may be altering SHBG. A diagnosis requires compatible symptoms and consistently low results—not one isolated number.
Take the 2-minute ED assessmentUnderstand the three measurements
These values answer related but different questions. They are most useful when interpreted together with symptoms and correctly timed testing.
Measures testosterone circulating in the blood, including testosterone bound to proteins and the smaller unbound portion.
This is generally the initial laboratory test. A low value should usually be repeated on a separate morning before diagnosing testosterone deficiency.
Estimates or measures the testosterone not bound to SHBG or albumin and therefore more readily available to tissues.
It is especially useful when total testosterone is borderline or may be misleading because SHBG is unusually high or low.
Sex hormone-binding globulin is a protein that binds testosterone and influences how total testosterone relates to free testosterone.
Without SHBG context, two men with similar total testosterone can have different calculated free testosterone values.
How results may fit together
These examples explain why one number should not be interpreted alone. They are not diagnoses.
Repeat an early-morning measurement and review symptoms before diagnosing testosterone deficiency.
Free testosterone and SHBG may help clarify whether androgen availability is also reduced.
Higher SHBG can sometimes leave less testosterone available to tissues despite a total value within range.
Lower SHBG can reduce total testosterone while free testosterone remains less affected, so clinical context matters.
A clinician may evaluate LH, FSH, prolactin and other factors to investigate why androgen levels are reduced.
ED can still be related to vascular, metabolic, medication, neurological, sleep or psychosexual factors.
For erectile health
Testosterone can influence sexual desire, morning erections and erectile physiology, but ED is not synonymous with low testosterone. Many men with ED have testosterone values that are not low, and hormonal testing does not replace evaluation of glucose, lipids, blood pressure, medicines, cardiovascular risk and psychological factors.
Testing correctly
Professional guidelines recommend early-morning testosterone testing, ideally in a fasting state. Testosterone varies by time of day, illness, sleep and other factors. When an initial result is low, a clinician generally confirms it with another morning measurement before making a diagnosis.
The StrideRX approach
ErectAware™ does not treat a single testosterone value as the answer. The panel combines total testosterone, free testosterone and SHBG with LH/FSH, prolactin, thyroid, glucose, HbA1c, lipids and other context. The Smart Report then explains patterns for specialist review.
Important limitation
Do not start testosterone or another hormone treatment based on one result or symptoms alone. Diagnosis and treatment require a qualified clinician, repeat testing when appropriate, evaluation of the cause and consideration of fertility, medical history and treatment risks.
Dr. Varun Arora, MD Psychiatry · Erectile Health Specialist and Specialist Sexologist
Last medically reviewed: 2026-07-17
Not routinely. Total testosterone is generally the initial test. Free testosterone and SHBG are most helpful when total testosterone is borderline, symptoms do not match the total value or altered SHBG is suspected.
Total testosterone includes testosterone bound to proteins plus the smaller unbound portion circulating in the blood.
Free testosterone is the unbound portion of circulating testosterone. It may be measured with a reliable method or calculated using total testosterone, SHBG and sometimes albumin.
SHBG binds testosterone. Higher or lower SHBG can change the relationship between total testosterone and the testosterone available to tissues.
Yes. This can occur when SHBG is higher, which is why clinicians sometimes add free testosterone and SHBG when symptoms and total testosterone do not match.
Yes. Lower SHBG can reduce total testosterone while free testosterone is less affected. The result still requires clinical interpretation.
Guidelines recommend early-morning testing, ideally fasting. A low result should usually be repeated on a separate morning.
No. Low testosterone can contribute, especially alongside low libido or reduced morning erections, but ED can also have vascular, metabolic, medication, neurological or psychosexual causes.
Usually no. Diagnosis requires compatible symptoms and consistently low testosterone, generally confirmed with at least one repeat morning measurement.
Yes. ErectAware™ includes total testosterone, free testosterone and SHBG alongside broader hormonal, metabolic, vascular, thyroid and inflammation context.