Energy and stress
Normal Cortisol Range: 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.
QUICK ANSWER
A typical UK lab range for a morning cortisol is 133 to 537 nmol/L, with midnight under 50. NICE reads a 9am result below 150 nmol/L as likely adrenal insufficiency, 150 to 300 as uncertain, and above 300 as 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 blood sugar, sharpens the morning, and fades by night.
1. What counts as a normal cortisol level in the UK?
There is no single normal number. UK practice uses three bands, all for a morning 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
These bands answer one question: whether your adrenal glands are underactive. They are not a stress score. The other adrenal marker people bring to this question is DHEA-S, and a low DHEA-S is usually explained by age rather than by your glands. A raised one is the reading clinicians actually order for, as high DHEA-S levels explains.
2. What reference range will your own lab print?
The NICE bands above are decision points. The range printed on your report is a different thing, and usually much wider.
Here is a typical one, published by the pathology service at Liverpool University Hospitals.
| Time of sample | Reference range |
|---|---|
| 6am to 10am | 133 to 537 nmol/L |
| Midnight | Below 50 nmol/L |
Notice how wide the morning band is. A 210 sits inside it, which is why nothing gets flagged, while the NICE table calls the same number uncertain. Both are correct, and they answer different questions.
9am cortisol chart, in both units
UK labs report nmol/L. American ones report µg/dL, so a 250 and a 9.1 can be the same blood. Divide nmol/L by 27.59 to move between them. Find your own number in the first two columns.
| nmol/L | µg/dL | How it reads |
|---|---|---|
| 100 | 3.6 | Under the NICE 150 line. A clinician should see it. |
| 150 | 5.4 | The lower NICE decision point. Above it, the result is uncertain rather than low. |
| 200 | 7.2 | Uncertain by NICE, inside a typical lab range. The band that comes back unflagged. |
| 250 | 9.1 | Still uncertain. A repeat is the usual next step. |
| 300 | 10.9 | The upper NICE decision point. Adrenal insufficiency is very unlikely. |
| 400 | 14.5 | Mid-range for a morning sample. |
| 537 | 19.5 | Top of the Liverpool morning range. Labs flag above their own ceiling. |
| 600 | 21.7 | Above a typical morning range. Illness, oestrogen, steroids and pain do this. |
Ranges differ between trusts, because each follows its own assay. Read your figure against the range printed beside it.
3. Why does the time of your test change the answer?
Because cortisol runs on a daily clock. It peaks within an hour of waking and bottoms out around midnight, where a healthy level can be a tenth of the morning one. Same glands, wildly different number.
That is why the 8am to 9am window exists. It catches the peak, when a low result means something. At 3pm a low number tells you almost nothing. Oxford University Hospitals biochemistry is blunt about it: a cortisol taken outside the 9am window is uninterpretable.
Age is the other thing people expect to matter here, and it matters less than the clock does. Cortisol levels by age covers what research says about the curve flattening over the decades, and why the printed range still does not move.
4. What makes a cortisol result read falsely high or low?
More things than most people expect, and none involve how stressful your week was. NICE flags these:
- 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. 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.
5. 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 and the needle itself can all lift it.
Persistently high cortisol from a gland problem is called Cushing's syndrome, and it is rare. One morning sample cannot screen for it. The usual test is overnight dexamethasone suppression, where a 9am cortisol below 50 nmol/L afterwards makes Cushing's very unlikely.
One raised morning reading is a prompt to look again, not a verdict. More in our guide to high cortisol symptoms.
6. 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 worth acting on. With a low morning cortisol, see a GP promptly rather than waiting for a repeat.
7. 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 is real. The label sends attention to one gland when the cause is usually elsewhere. Thyroid, iron and B12 all produce that same flat 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. Before any of that, it is worth checking what causes low energy levels in most people, because sleep and caffeine come first.
8. Which blood test reports your cortisol
The marker is simply called cortisol, measured in nmol/L. Timing rules the result, so take the sample between 8am and 9am.
Helvy's General Energy & Wellness panel (£149) reports cortisol alongside TSH, free T4, vitamin D, B12, magnesium, CRP and kidney and liver markers. That grouping is deliberate. When you are tired, cortisol is rarely the answer alone.
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 reports 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 it very unlikely. Lab ranges vary by assay, so read your number against 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 a repeat. If it stays there, the next step is endocrinology advice or a short synacthen test, read alongside your symptoms.
How do I convert cortisol from µg/dL to nmol/L?
Multiply by 27.59. So a 9am cortisol of 9 µg/dL is about 250 nmol/L, and 15 µg/dL is about 414 nmol/L. UK reports use nmol/L, so check your unit before comparing against an American chart.
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.