Measuring cortisol under long-term stress: what does it say?

What cortisol does in your body

Cortisol is made in the adrenal glands, driven by the pituitary. It is not a bad hormone: you need it to get going in the morning, to keep your blood sugar stable and to respond to strain.

Its release follows a clear daily rhythm. Production peaks in the early morning, then falls gradually to a low point at night. Acute strain temporarily adds to it.

That rhythm is exactly why the timing of the draw matters so much. The same person produces a very different result in the morning than at the end of the afternoon.

What a cortisol measurement does answer

A morning cortisol in blood is meant to assess whether the axis between pituitary and adrenals is working. The question is: does your body make enough, or too much, of this hormone?

That is a medically relevant question. Structurally low or structurally high production belongs with a doctor and calls for follow-up testing, because both pictures can have serious consequences.

What the measurement does not do is measure your stress level. There is no blood value that tells you how much pressure you feel, how hard you are merely coping or how close you are to burnout.

Why adrenal fatigue is not a diagnosis

Online you often meet the idea that the adrenals become exhausted after long-term stress and start producing too little cortisol. That model has never been scientifically confirmed and is not used as a diagnosis in mainstream medicine.

What does exist is adrenal insufficiency: a condition in which production genuinely falls short. It is rare, causes a different pattern of complaints and is established by a doctor with specific tests.

That does not make your complaints any less real. Persistent exhaustion after a long period of overload is genuine, but the explanation lies more often in sleep, recovery, mood and lifestyle than in a single hormone value.

What can distort your result

Cortisol is sensitive to circumstances. Take into account:

• The timing: have blood drawn in the morning, preferably between seven and ten, and at the same time when repeating.
• Corticosteroids, including inhalers, skin creams or injections. These can suppress your own production.
• The contraceptive pill and other oestrogens, which raise the protein cortisol binds to in blood.
• Pregnancy, where the same mechanism applies.
• Acute illness, fever, surgery or severe pain, which temporarily push the value up.
• Lack of sleep, night shifts and alcohol, which shift the daily rhythm.

Always report which medication you use and what your recent nights were like. Without that context a result is hard to interpret.

Which values more often yield something under long-term stress

Complaints attributed to chronic stress strikingly often have another measurable cause. These tests yield more in practice:

• TSH and free T4, because a thyroid out of balance causes the same exhaustion or restlessness
• ferritin, certainly in women with heavy periods
• vitamin B12 and folate, involved in energy and blood formation
• vitamin D, which often comes out low in the Netherlands
• glucose and HbA1c, because swinging blood sugars cause fatigue and irritability
• a full blood count, which reveals anaemia and infection

If something is found there, you have something concrete to work with. If nothing is found, that is information too: it shifts attention to recovery, sleep and workload rather than to a deficiency that is not there.

When measuring is useful

A cortisol test mainly makes sense when there is a concrete suspicion, for example persistent extreme fatigue with dizziness on standing, unintended weight loss, or conversely rapid weight gain around the waist with thin skin and easy bruising.

With an ordinary busy life and too little sleep, the test usually adds little. The chance is high that you receive a normal result while your complaints persist, and that does not move you forward.

If you sit somewhere in between, a broader package is often wiser than a single value. In one draw you then look at several possible causes at once. If you are unsure which combination fits, the test finder will point you in the right direction.

How it works at Bloodworks

At Bloodworks you have cortisol measured without a referral, at one of the more than 800 affiliated collection points across the Netherlands. You choose your moment, and for cortisol we advise a morning draw.

If you want to look more broadly, the Fatigue & Sleep package contains eight tests: TSH and free T4, ferritin, vitamin B12, folate, vitamin D, morning cortisol, magnesium and a full blood count. Your result is reviewed by a doctor and reaches you as a personal PDF report, typically within 2 working days.