Which Indicators Should You Check for Testosterone? A Complete Guide to Hormone Testing for Middle-Aged Men

When checking testosterone, the most basic tests are Total Testosterone and Free Testosterone. Total testosterone includes both bound and free forms, but free testosterone is the active portion that can actually enter cells and exert effects. Many middle-aged men have total testosterone within the reference range but low free testosterone, yet symptoms are obvious, so looking only at total testosterone can easily miss the diagnosis.

In addition to these two core markers, you also need to check sex hormone-binding globulin (SHBG), luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin, estradiol, and prostate-specific antigen (PSA). SHBG binds testosterone and affects the free fraction; LH and FSH reflect the brain's instructions to the testes; high prolactin suppresses testosterone; estradiol is a conversion product of testosterone, and both too high and too low are problematic; PSA is a basic screening for prostate health.

Testosterone secretion is regulated by the hypothalamic-pituitary-gonadal axis. The hypothalamus releases GnRH, which stimulates the pituitary to secrete LH and FSH; LH then stimulates Leydig cells in the testes to produce testosterone. If testosterone is low, the brain increases LH secretion to compensate, so elevated LH suggests primary hypogonadism (testicular dysfunction). If LH is normal or low, the problem may lie in the pituitary or hypothalamus (secondary hypogonadism).

SHBG is synthesized by the liver and binds tightly to testosterone, preventing it from entering tissues. Obesity, hyperthyroidism, liver disease, and aging all raise SHBG, leading to normal total testosterone but low free testosterone. Estradiol is produced from testosterone via the aromatase enzyme; adipose tissue is rich in aromatase, so obese men tend to have higher estradiol, which further suppresses testosterone through negative feedback. High prolactin suppresses GnRH secretion, leading to decreased LH and FSH, and consequently lower testosterone.

Testing testosterone is not just a single blood draw; it requires following a standard protocol, otherwise results may be misleading. The following steps can help you obtain reliable data.

Step 1: Choose the right time. Have your blood drawn between 8 and 10 a.m., as testosterone peaks in the morning. If you work night shifts or have irregular sleep patterns, try to have blood drawn within 2-3 hours of waking, and record your sleep schedule.

Step 2: Fast before the test and ensure adequate sleep the night before. Lack of sleep can significantly lower testosterone, so aim for at least 7 hours of sleep the night before the test. Fasting typically means no food for 8-12 hours, though you may drink small amounts of plain water.

Step 3: Test at least twice. Because testosterone levels fluctuate, a single result is not reliable. Wait 1-2 weeks and test again, then take the average of the two results. If the two results differ significantly, a third test may be needed.

Step 4: Test a full panel simultaneously. Do not just order total testosterone; include free testosterone (or calculated free testosterone), SHBG, LH, FSH, prolactin, estradiol, and PSA. If free testosterone is not directly measured, it can be calculated from total testosterone and SHBG.

Step 5: Record symptoms and lifestyle. Before the test, record your energy, libido, mood, sleep, training status, etc., so your doctor can make a comprehensive assessment. Do not rely solely on numbers.

Men who should get a full testosterone panel include: men over 40 with noticeable symptoms of low testosterone (such as decreased libido, fewer morning erections, reduced energy, muscle loss, or low mood); those with chronic conditions like diabetes, obesity, or metabolic syndrome; those taking medications that may affect hormones (such as glucocorticoids or opioids); and men undergoing fertility evaluation or planning for pregnancy.

People who do not need or are not suitable for a full panel: those without symptoms and with normal total testosterone do not need additional free testosterone testing; those with acute illness or recovering from recent surgery, because stress can temporarily lower testosterone; and those taking medications that affect hormones (such as androgens), as results will not reflect baseline levels.

If you have symptoms of low testosterone lasting for several weeks or more and affecting your quality of life, you should see a doctor. These symptoms include: significantly decreased libido, erectile dysfunction, loss of morning erections, persistent fatigue, depression, decreased muscle mass, and loss of body hair.

Additionally, if a physical exam reveals total testosterone below the lower limit of the reference range (typically 8–10 nmol/L or 250–300 ng/dL), or low free testosterone, further testing is recommended even without symptoms. If LH and FSH are elevated, it suggests testicular failure, and you should see an endocrinologist; if prolactin is significantly elevated, a pituitary adenoma should be ruled out.

Misconception 1: Only looking at total testosterone. Normal total testosterone does not mean free testosterone is normal; elevated SHBG can mask the true picture. Misconception 2: Drawing conclusions from a single result. Testosterone has circadian rhythm and daily fluctuations; a single low value may be coincidental. Misconception 3: Not adjusting lifestyle before testing. Staying up late, drinking alcohol, and intense exercise can affect results; maintain a regular routine before testing. Misconception 4: Believing that low testosterone always requires supplementation. In fact, lifestyle interventions (sleep, training, fat loss) can often improve it, and testosterone supplementation should be evaluated by a doctor.