Cortisol: Values, the Daily Rhythm and Reading the Report
Cortisol is a hormone the adrenal gland releases on a daily rhythm: there is most of it in the morning, around waking, and least of it around midnight. A cortisol result therefore has no single “normal value”; it depends on the hour the blood was taken, on whether you slept that night and on the medicines you take. This article covers the reference values, what a raised and what a lowered result mean, which further tests a doctor orders and when the right moment for an endocrinologist has come.
Normal cortisol values in the blood
Values are reported in nmol/L or in µg/dL (1 µg/dL is about 27.6 nmol/L). The ranges differ a little from laboratory to laboratory, so a result is always read against the reference range printed beside it.
| Sample | Usual reference range | Note |
|---|---|---|
| Morning cortisol (7 to 9 h) | about 170 to 540 nmol/L (6 to 19 µg/dL) | The basic test. Taken fasting, after a night of normal sleep. |
| Afternoon cortisol (16 to 18 h) | about 65 to 330 nmol/L (2.5 to 12 µg/dL) | It should be clearly lower than the morning value; that is a healthy daily rhythm. |
| Salivary cortisol at midnight | below the laboratory's cut-off | The test for suspected overproduction: night-time cortisol should be close to zero. |
| Free cortisol in a 24-hour urine collection | by laboratory | Measures total daily production rather than a single moment. |
The first rule of interpretation: one afternoon or randomly taken cortisol result means almost nothing on its own. An endocrinologist asks for a morning sample at a precise time and, where a disorder is suspected, for dynamic tests that show how the gland responds rather than just how much hormone there is at that moment.
Raised cortisol: what usually pushes it up
In most people a mildly to moderately raised morning cortisol has nothing to do with disease of the adrenal gland. The most common reasons are everyday ones:
- Poor sleep and night work. A short or broken night shifts the whole rhythm and the morning sample comes out higher than it really is.
- Acute stress, illness, fever, a hard workout the day before. Cortisol is the hormone of the response to load and rises exactly when it should.
- Hormonal contraception and pregnancy. Estrogen raises the protein that binds cortisol, so total cortisol in the blood goes up even though the active part is normal. This is one of the most common reasons for a “raised cortisol” in younger women.
- Obesity, depression, alcohol. All three conditions chronically raise the stress axis.
- Medicines containing cortisone in any form, including creams and inhalers, distort the result in either direction depending on when they are taken.
Genuine disease with an excess of cortisol, Cushing's syndrome, is rare. It is considered when a high cortisol comes with the typical signs: a rounded red face, fat building up on the abdomen and neck with thin arms and legs, purple stretch marks, muscle weakness, bruising for no reason, raised blood pressure and blood sugar. The endocrinologist then runs a dexamethasone suppression test, a night-time salivary cortisol or a 24-hour urine collection, and only makes the diagnosis on the basis of those.
Low cortisol: when it matters
A low morning cortisol is a clinically more important finding than a mildly raised one. The causes are underactivity of the adrenal gland itself (Addison's disease), damage to the pituitary that drives the gland, or an abrupt stop to longer corticosteroid treatment, after which the gland is left “asleep”. The symptoms are fatigue that rest does not fix, weight loss, low blood pressure and dizziness on standing, nausea, craving for salt and, in Addison's disease, darkening of the skin.
A morning cortisol below about 100 nmol/L (3.6 µg/dL) calls for urgent checking, values between 100 and 400 nmol/L are a “grey zone” in which the doctor runs a stimulation test with ACTH, and a result above 400 to 500 nmol/L practically rules insufficiency out. That is why, with fatigue and weakness, cortisol is one of the tests an endocrinologist genuinely uses, alongside the thyroid, the blood count and iron.
“Cortisol belly”, “detox” and pills for cortisol
Three things you will read on the internet that the evidence does not support. Fat building up on the abdomen has many causes, and cortisol is only one of them and rarely the main one; “cortisol belly” is not a diagnosis and is not treated with supplements. No “detox” lowers cortisol, because it does not accumulate like a poison but is released as needed. And finally, supplements that promise to “regulate cortisol” have no evidence that they change the result; what does change it is sleep, less alcohol, movement and treating the underlying condition when there is one.
What an endocrinology appointment looks like
The endocrinologist first looks at the whole picture rather than one number: when the blood was taken, what your sleep was like that night, which medicines and which contraception you take, and what your blood pressure, blood sugar and weight are. If an excess or a shortage of cortisol is suspected, you are given instructions for a dynamic test, which follows a precise protocol, and a follow-up with the result. If the finding has an everyday explanation, you get that explanation and a plan to deal with whatever is behind the fatigue or the weight in the right place.
At the Miren Medic clinic endocrinology appointments are held by Dr Zorana Đuran and Dr Nemanja Nenezić, subspecialists in endocrinology, without a referral. Hormone tests, including cortisol, ACTH, the thyroid and the sex hormones, are run in the clinic laboratory, so the result and its interpretation can come from the same place. More about the service on the endocrinologist Belgrade page.
Prices
| Service | Price |
|---|---|
| Endocrinology appointment (Dr Zorana Đuran) | 7.000 RSD |
| Endocrinology appointment (Dr Nemanja Nenezić) | 12.000 RSD |
| Endocrinology appointment + ultrasound of the thyroid | 12.000 to 14.000 RSD |
| Follow-up appointment (Dr Nenezić) | 10.000 RSD |
Frequently asked questions
What are normal cortisol values in the morning?
Morning cortisol taken between 7 and 9 o'clock is most often between 170 and 540 nmol/L, that is 6 to 19 µg/dL. The range depends on the laboratory, so a result is read against the reference values printed beside it, and afternoon cortisol is normally considerably lower.
What does a raised cortisol in the blood mean?
Most often poor sleep, stress, illness, hormonal contraception, pregnancy, obesity or alcohol. Cushing's syndrome is only considered when a high cortisol comes with the typical signs, and the endocrinologist then runs a dexamethasone suppression test or a night-time salivary cortisol before concluding anything.
Is low cortisol dangerous?
It can be. A morning cortisol below about 100 nmol/L with fatigue, low blood pressure, weight loss and nausea calls for prompt checking by an endocrinologist, because it can mean underactivity of the adrenal gland. Values in the grey zone are checked with a stimulation test.
How should I prepare for a cortisol test?
Blood is taken in the morning, between 7 and 9 o'clock, fasting, after a night of normal sleep and with no hard training the day before. Tell the doctor in advance if you take contraception, corticosteroids in any form or biotin, because all of those change the result.
Does cortisol affect weight and the abdomen?
Chronically raised cortisol can contribute to fat building up on the abdomen, but in most people carrying extra weight cortisol is not the cause. “Cortisol belly” is not a diagnosis, and supplements that promise to bring it down have no evidence that they change the result.
Which doctor interprets a cortisol result?
An endocrinologist. They assess the result together with the time of sampling, your medicines and your symptoms, and where a disorder is suspected they order dynamic tests. At the Miren Medic clinic the appointment is booked without a referral.
Book an appointment
If your cortisol result is outside the range, or fatigue, blood pressure and weight are troubling you for no clear reason, book an endocrinology appointment at the Miren Medic clinic. The hormone tests and the interpretation come from one place, without a referral.
