Energy and stress
Normal Cortisol Levels: What a 9am Result Means
Reviewed by a qualified clinician · analysed at UKAS-accredited UK labs (ISO 15189)
Last reviewed August 20267 min read
Every Helvy guide is written by our health editors, then checked by a qualified clinician before it goes live and re-checked as the science moves. We name clinical roles, not individuals, until each reviewer has agreed to be credited publicly. This is wellness guidance to help you understand your own data, not a diagnosis.
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In the UK, cortisol is measured in blood, usually between 8am and 9am. NICE reads a result below 150 nmol/L as likely adrenal insufficiency. Between 150 and 300 nmol/L is uncertain. Above 300 nmol/L, adrenal insufficiency is very unlikely. Cortisol swings through the day, so the time on the tube matters as much as the number.
Not sure which markers you need? Build your test →Your cortisol comes back at 210 nmol/L. The report says nothing is flagged. You have been tired for months, and 210 sounds low to you. So what does that number actually mean?
Cortisol is the hormone your adrenal glands release to get you through the day. It lifts your blood sugar, sharpens you in the morning, and fades by night. This guide covers the UK thresholds, why the clock matters, and what a result in the middle really says.
1. What counts as a normal cortisol level in the UK?
There is no single normal number. UK practice uses three bands, and they apply to a morning blood sample. In 2024, NICE published guideline NG243 and set them out in a table.
| Result | What it means |
|---|---|
| Below 150 nmol/L | You may have adrenal insufficiency. Referral to endocrinology. |
| 150 to 300 nmol/L | Uncertain. Repeating the test is the usual next step. |
| Above 300 nmol/L | Adrenal insufficiency is very unlikely. |
“Offer an 8 am to 9 am serum cortisol test to people aged 1 year and over with suspected adrenal insufficiency.”
— NICE guideline NG243, recommendation 1.2.9
Two things follow from that table. These bands answer one question, which is whether your adrenal glands are underactive. They are not a stress score. And NICE notes the cut-offs only apply to modern immunoassays, so your own lab range is the one to read against.
2. Why does the time of your test change the answer?
Because cortisol runs on a daily clock. It peaks within an hour of waking, drops through the afternoon, and bottoms out around midnight. A healthy midnight level can be a tenth of the morning one. Same person, same glands, wildly different number.
That is why the 8am to 9am window exists. It catches the peak, when a low result is meaningful. Take the sample at 3pm and a low number tells you almost nothing. Oxford University Hospitals biochemistry is blunt about it: a cortisol taken outside the 9am window is uninterpretable.
3. What makes a cortisol result read falsely high or low?
More things than most people expect, and none of them involve how stressful your week was. NICE flags these directly:
- Oral oestrogen. It raises the carrier protein cortisol travels on, so the total reads high. NICE advises stopping it for six weeks before the test.
- Steroid medication. Inhaled, topical and injected steroids all count, not just tablets.
- A recent steroid injection. NICE says wait four weeks after an intramuscular or joint injection.
- Being acutely unwell. Illness pushes cortisol up, so a result taken mid-infection is hard to read.
The oestrogen one catches people out often. If you take a combined pill or oral HRT, say so before the blood is drawn. Our guide on supplements that affect blood tests covers the same trap from the other side.
4. What does a high cortisol result mean?
Usually less than the internet suggests. A morning cortisol above the range is common and rarely sinister. Illness, oral oestrogen, pain, a hard workout before the appointment and even the stress of the needle can lift it.
Persistently high cortisol from a gland problem is called Cushing's syndrome, and it is rare. Testing for it does not use a single morning sample. The usual screen is an overnight dexamethasone suppression test. A 9am cortisol below 50 nmol/L afterwards makes Cushing's very unlikely.
One raised morning reading on its own is a prompt to look again, not a verdict. Read more in our guide to high cortisol symptoms.
5. What does a low cortisol result mean?
A morning cortisol under 150 nmol/L needs a doctor to look at it. That is the NICE threshold for suspecting adrenal insufficiency, where the glands do not make enough. The best known form is Addison's disease.
The symptoms are vague on their own and specific together. Watch for this cluster:
- Tiredness that rest does not fix.
- Weight loss you did not intend.
- Dizziness on standing, or low blood pressure.
- Craving salt.
- Darkening skin, especially in creases and old scars.
Those last two are the ones worth acting on. If you have them alongside a low morning cortisol, see a GP promptly rather than waiting for a repeat test.
6. Does adrenal fatigue show up on a cortisol test?
No, and the honest version of this matters. Adrenal fatigue is not a recognised medical condition in the UK. No NHS or NICE guideline defines it, and no cortisol pattern diagnoses it.
The tiredness people describe is real. The label is the problem, because it sends attention to one gland when the cause is usually elsewhere. Thyroid, iron and B12 all produce exactly that kind of flat, unrefreshed exhaustion.
So the useful move is to widen the test, not narrow it. Our adrenal fatigue blood test guide takes that label apart properly, our guide for when you are always tired covers what to check first, and the energy and fatigue hub collects the rest.
7. Which blood test reports your cortisol
The marker is simply called cortisol, measured in nmol/L. Because timing rules the result, book or post your sample so it is taken between 8am and 9am.
Helvy's General Energy & Wellness panel (£149) reports cortisol alongside TSH, free T4, vitamin D, vitamin B12, magnesium, CRP and kidney and liver markers. That grouping is deliberate. When someone is tired, cortisol is rarely the answer on its own.
One honest limit. We measure cortisol in blood, not saliva, so we do not map your full daily curve. A morning blood cortisol answers the question NICE asks of it. To pick your own markers, the build-my-test tool walks you through it.
READY TO TEST?
See your cortisol next to everything it travels with
Helvy's home blood tests report cortisol with plain-English context, so a number in the middle does not leave you guessing. Samples are processed by UKAS-accredited UK labs.
Frequently asked questions
What is a normal cortisol level in the UK?
For an 8am to 9am blood sample, NICE reads below 150 nmol/L as likely adrenal insufficiency, 150 to 300 nmol/L as uncertain, and above 300 nmol/L as making adrenal insufficiency very unlikely. Lab reference ranges vary by assay, so read your number against the range printed on your own report.
Is a cortisol of 200 nmol/L low?
It sits in the uncertain band. NICE treats 150 to 300 nmol/L at 9am as neither reassuring nor alarming, and suggests repeating the test. If it stays there, the next step is endocrinology advice or a short synacthen test. A qualified clinician should read it alongside your symptoms.
What time of day should cortisol be tested?
Between 8am and 9am. Cortisol peaks shortly after you wake and falls to its lowest around midnight, so a sample taken later in the day cannot be compared against the standard thresholds. If you work nights, aim for about an hour after waking instead.
Can stress make your cortisol test come back high?
Short-term stress does move cortisol, including the stress of the blood draw itself. But everyday work pressure does not usually push a morning result outside the reference range. Illness, oral oestrogen, steroid medication and recent hard exercise are more common explanations.
Does HRT or the pill affect a cortisol blood test?
Oral oestrogen does. It raises the protein cortisol binds to, so the total measured cortisol reads falsely high. NICE advises stopping oral oestrogen for six weeks before the test, and suggests considering a patch or gel instead if it is being taken as HRT. Do not stop any prescribed medication without asking your prescriber.
Is adrenal fatigue a real diagnosis?
Not in UK medicine. No NHS or NICE guideline recognises it, and no cortisol pattern confirms it. The tiredness is real, but the cause is more often thyroid, iron or B12. Testing those markers together is more useful than testing cortisol alone.
Related guides
Cortisol Blood Test UK
What the test measures, how it is taken, and what happens next.
High Cortisol Symptoms
What raised cortisol feels like, and what usually explains it.
Low Cortisol Symptoms
The cluster of signs that makes a low morning result worth acting on.
Cortisol and Sleep
How the daily curve and your sleep pattern move together.
Adrenal Fatigue Blood Test UK
What the label means, and what the tests can honestly show.
Blood Test Reference Ranges UK
Why normal on a lab report is a population range, not a target.