Getting your testosterone test right

Why one test isn't enough

Testosterone rises and falls through the day and varies from one day to the next. It's also temporarily lowered by illness, very poor sleep, intense exercise and some medications. A single low result is frequently normal when repeated.

That's why the AUA's guideline strongly recommends confirming low testosterone with two morning measurements on separate occasions before diagnosing deficiency.

Timing: the morning rule

Testosterone is highest in the morning in most men. MedlinePlus notes that blood is usually drawn between about 7 and 10 a.m. A sample taken mid-afternoon can read meaningfully lower and make a normal man look deficient.

If you work night shifts, ask your clinician how to time the test; draws are usually done shortly after your main sleep period.

Before your blood draw

• Book a morning appointment and keep it consistent for repeat tests.
• Ask whether to fast. Some guidelines suggest fasting, since a large meal can lower testosterone briefly, and fasting also allows glucose and lipids to be measured.
• Avoid testing during or just after an acute illness, surgery or a period of unusual stress.
• Try to sleep normally the night before.
• Skip unusually intense or prolonged exercise the day before.
• Tell your clinician about all medications and supplements, including opioids, steroids, hormone products and biotin.
• If you're already on testosterone, follow your clinician's instructions on timing relative to your dose.

Total, free and bioavailable testosterone

Total testosterone measures both bound and unbound hormone and is the standard first test. Most testosterone in blood is attached to proteins, mainly SHBG and albumin.

When SHBG is unusually high or low, total testosterone can mislead. SHBG tends to be lower with obesity and type 2 diabetes and higher with aging, liver disease and an overactive thyroid. In those situations, a free testosterone level, ideally measured by a reliable method or calculated from total testosterone and SHBG, adds useful context.

Tests that usually go with it

• LH, and sometimes FSH, to see whether low testosterone starts in the testes or in pituitary signaling
• Prolactin, when testosterone is low with low or low-normal LH
• Hemoglobin and hematocrit, before any therapy
• PSA in men over 40, before any therapy
• Thyroid, glucose or A1C, and lipids, to look for conditions that mimic or cause low testosterone

Lab methods and reference ranges

Different labs use different methods and slightly different reference ranges. Mass spectrometry methods are generally more accurate at low levels than some older immunoassays. For repeat testing, using the same lab makes comparisons more meaningful.

Home finger-prick kits can be convenient, but results should be confirmed with a standard venous blood test before any treatment decision.

Common mistakes that skew results

Testing in the afternoon, testing once and stopping, testing while recovering from flu, or comparing results from labs with different methods are the most frequent problems. Each can make a normal man look deficient or hide a true low.

Another mistake is testing only testosterone. Without LH and, where relevant, prolactin, it's hard to know why a level is low, which matters for choosing treatment and protecting fertility.

Monitoring once on treatment

If you start testosterone therapy, testing continues. Levels are checked after starting and after dose changes, then periodically; the AUA suggests every 6 to 12 months once stable. Hematocrit and PSA are monitored too, and blood pressure should be checked because the FDA now requires labeling about blood pressure increases.

What happens next

If two morning results are low and your symptoms fit, your clinician will look at LH and other tests to understand why, and discuss options. If results are normal or only borderline, attention usually turns to sleep, weight, alcohol, mood and medications. At HealifyMD, the Comprehensive Lab Panel is $199 one-time, and prices are confirmed at your eligibility review.

See a doctor in person promptly if testing reveals very low testosterone with headaches or vision changes, or if you notice a testicular lump.