Cortisol and exercise: why a hard workout raises it and why it matters for a test

Yes, exercise can raise cortisol, mostly when it is hard enough to be a real strain. The rise is short and normal. It is not a sign of illness. It matters in one practical place: a cortisol blood test taken soon after a hard session.

Does exercise increase cortisol?

Cortisol is part of the body’s response to physical strain. A review of exercise research says its main job during exercise is to make fuel available for working muscles (Sports Medicine - Open, 2017). The same review says cortisol rises with a single bout of exercise only when the intensity passes a threshold.

A 2025 paper gives a number from earlier work. In adults, saliva cortisol rose steadily over 15 minutes of exercise at 70 to 85 percent of maximum heart rate, and showed no significant change at lower intensities. The authors also say that the peak comes roughly 20 to 30 minutes after exercise ends (Sports Medicine - Open, 2025). Treat the percentages as one study’s finding, not a rule.

Does running or HIIT raise it?

We found no source we can use that tests running on its own, so this page makes no running-specific claim. The pattern above is the part to take from it. Harder sessions are the ones that tend to show a rise.

For high-intensity interval training, one study had 25 male college students do a single session of ten one-minute cycling bursts at the power that matched their peak oxygen uptake. Blood cortisol was significantly higher straight after the session than before it, and higher again 30 minutes later (Int J Environ Res Public Health, 2020). It was a small study in young men, and it doesn’t show what the same session does in other people.

Intensity isn’t the only factor. In the 2025 study, 61 students did 15 minutes of coordination exercise and, a week later, 15 minutes of endurance exercise at a similar heart rate. The coordination session produced a higher cortisol release. The authors link that to its extra mental demand. They also note that cortisol responses vary a lot between people.

How long does the rise last?

The 2025 paper, citing earlier literature, puts the peak at about 20 to 30 minutes after exercise ends. We found no source we can use that says exactly when levels return to your usual range, and it will vary with how hard the session was.

The 2017 review also notes, citing earlier studies, that after exhaustive exercise, cortisol may stay low for 24 to 48 hours in some studies, and that using cortisol to spot overtraining hasn’t produced consistent findings. A separate part of that review looked at the cortisol rise that follows waking. Across 32 studies the effects varied, and the authors could not combine them.

Exercise and a cortisol test

This is where the topic matters to most readers.

• MedlinePlus says stress and exercise can raise your cortisol levels, so you may need to rest before your test.
• Cortisol also follows a daily rhythm, so the time of the draw matters as much as the workout. See AM and PM cortisol timing.
• Tell the person ordering the test, and the lab, if you exercised hard before the draw. Follow the instructions on your lab order over anything on this page.

A result that is higher after exercise isn’t automatically a problem. MedlinePlus says abnormal cortisol results don’t always mean a medical condition that needs treatment, and that a cortisol test alone can’t diagnose the cause. A single result also can’t diagnose or rule out Cushing’s syndrome or adrenal insufficiency. See normal cortisol levels.

When to see a clinician

Feeling tired after a hard session is normal. See a clinician if you have fatigue, muscle weakness or weight loss that lasts and has no clear reason. NIDDK lists these among the most common symptoms of adrenal insufficiency, along with loss of appetite and abdominal pain. It also lists low blood pressure that drops further when you stand, with dizziness or fainting. NIDDK’s advice is to ask a health care professional if you always feel tired, weak or are losing weight. That doesn’t mean your tiredness is adrenal. Many other causes are more common. See low cortisol symptoms and cortisol and fatigue.

Vomiting you can’t stop, fainting or severe weakness need urgent care, not a test. See adrenal crisis. If you take a steroid medicine, don’t change it yourself. Ask your prescriber.

Keep reading

• AM and PM cortisol timing

  When the samples are taken and why timing matters.

• Cortisol awakening response

  The rise after waking and what changes it.

• What cortisol does

  The jobs cortisol does in the body.

• Cortisol and fatigue

  When tiredness is and isn't about cortisol.