Hormones

Cortisol

Included in Baseline and Complete.

Cortisol rises and falls with your daily rhythm.

Cortisol is made by your adrenal glands and helps regulate blood sugar, blood pressure, metabolism, and your response to stress. A blood test shows your level at one point in its daily rhythm.

Timing shapes every cortisol result.

Cortisol starts rising in the final hours of sleep, peaks around waking, and falls to its lowest point at night. That's why blood cortisol is usually drawn in the morning, and why a later draw can read lower without anything being wrong.

Stress, illness, exercise, and pregnancy can all shift a single reading. Birth control pills and oral estrogen raise the protein that carries cortisol, which raises total cortisol. Steroid medicines such as prednisone can suppress your own cortisol production, and some can also affect the test itself.

One cortisol result is a snapshot of a moving daily curve.

Questions

Can a blood cortisol test tell me how stressed I am?

It can't do that reliably. Cortisol responds to many things, including exercise, illness, and the time of the draw, so one result doesn't measure everyday stress. It's more useful for helping a clinician decide whether your adrenal glands need a closer look.

What if my cortisol is high or low?

An unusual result usually leads to a repeat test or more specific testing, because a single blood cortisol isn't enough to diagnose conditions such as Cushing's syndrome or adrenal insufficiency. Tell your clinician about steroid medicines, hormonal birth control, and biotin supplements, since these can affect results.

Sources and references