Stress and energy markers
Cortisol Levels by Age: The Clock Beats the Calendar
Reviewed by a qualified clinician · analysed at UKAS-accredited UK labs (ISO 15189)
Last reviewed September 20266 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
UK labs do not publish a cortisol range by age. They publish one adult range by time of day. Royal Liverpool reads 133 to 537 nmol/L for a sample taken between 6am and 10am, and under 50 at midnight. The hour on your form moves the number far more than your age does.
Not sure which markers you need? Build your test →Your cortisol came back at 210. You are 48, you are exhausted, and you want to know what 210 looks like for someone your age.
Here is the thing nobody tells you on the report. Cortisol is the hormone your adrenal glands release on a daily rhythm, high in the morning and low at night. UK labs read it against the clock, not against your birthday. This guide covers what they print, what genuinely shifts with age, and how to read 210 properly.
1. Is there a cortisol chart by age?
Not in UK pathology. Look through NHS test directories and you find ranges split by the hour of the draw. You do not find a band for your thirties and another for your sixties.
That is deliberate. Cortisol swings by several hundred nanomoles across a single day. Any difference between two age groups sits inside that daily swing, so splitting the range by decade would add noise rather than accuracy.
2. What UK labs actually print
Cortisol is reported in nanomoles per litre, written nmol/L. Here is what two NHS sources publish for adults. The other adrenal marker is handled the opposite way, since labs band DHEA-S by decade, which is why a low DHEA-S depends entirely on your age.
| Sample time | Figure | Source |
|---|---|---|
| 6am to 10am | 133 to 537 | Royal Liverpool |
| Midnight | below 50 | Royal Liverpool |
| 9am, clinical threshold | above 300 is reassuring | Oxford University Hospitals |
Look at the gap between the first two rows. The same person can read 500 at breakfast and 40 at midnight, and both are ordinary. No age chart could survive a spread like that.
3. Why the time of your test decides the number
Cortisol peaks shortly after you wake and falls through the day. Oxford University Hospitals is blunt about what that means for a result taken at the wrong hour.
“A random (non-09:00am) cortisol … is uninterpretable.”
— Oxford University Hospitals, clinical biochemistry
The same page gives the thresholds clinicians work to at 9am. Under 150 nmol/L prompts further testing. Between 150 and 300 is indeterminate and may be normal. Above 300 makes low adrenal output very unlikely.
One morning figure is one moment, and clinicians treat it that way. When a 9am result lands in that middle band, the usual next step is a stimulation test rather than a repeat. That is a hospital procedure, not a home one. Worth knowing, so a borderline number does not send you hunting for a second opinion you do not need yet.
So a 210 at 9am is a shrug, not an answer. A 210 at 4pm is a different shrug. Note your sample time, because without it the number cannot be read. Our normal cortisol levels guide works through high and low results in more detail.
4. What does change as you get older
The printed range stays put. The daily curve does not. A study in Psychoneuroendocrinology followed 185 adults aged 20 to 81, sampling saliva seven times a day for ten days.
It reported that older age was associated with increased daily cortisol output, a flatter slope from waking to evening, and a more pronounced rise in the first half hour after waking. In plain terms, the older curve is higher overall and less steep.
Two things follow from that, and both are practical rather than alarming.
- An evening cortisol tends to sit a little higher later in life, so the day flattens out.
- A single morning number still lands inside the same adult range, which is why labs never split it.
Age also changes what you are doing on the morning of the test. Retirement moves wake times. Medication lists grow. Sleep gets lighter and shorter. Each of those nudges a morning cortisol on its own, and none of them is a change in your adrenal glands.
That research used saliva, and Helvy measures cortisol in blood. The two are not interchangeable figures. The shape of the finding holds, the numbers do not transfer. It also describes a population rather than a person.
5. What lifts cortisol when nothing is wrong
Plenty. Royal Liverpool names three straight away: pregnancy, the combined oral contraceptive pill, and stress. All three raise the measured figure without anything being wrong with your adrenal glands.
Add the ordinary ones. A poor night’s sleep, a hard training session, an illness, or the drive to the clinic can all nudge the number. Steroid treatment makes a result uninterpretable, which is why Oxford names it alongside the wrong sample time.
This is also why the phrase adrenal fatigue does not appear on a lab report. It is not a recognised diagnosis, and what a blood test can and cannot show about adrenal fatigue covers where the idea came from.
6. Which blood test reports your cortisol
The marker is cortisol, reported in nmol/L. Helvy's General Energy & Wellness panel (£149) reports it alongside thyroid, vitamin D, vitamin B12, magnesium, CRP, kidney and liver markers and a full lipid set. That matters, because tiredness rarely has one number behind it.
Take your sample in the morning and note the time when you register the kit. A blood test measures biomarkers and offers wellness insight; it does not diagnose. If your result sits outside the range on your report, take it to a qualified clinician.
If sleep is the part that has gone wrong, cortisol and sleep covers the rhythm in more depth. The build-my-test tool helps you pick markers.
READY TO TEST?
See your cortisol with the time of day attached
Helvy's home blood tests report cortisol in UK units with plain-English context, read against the hour you sampled rather than a generic range. Samples are processed by UKAS-accredited UK labs.
Frequently asked questions
What is a normal cortisol level by age?
UK labs do not publish one. They publish a single adult range by sample time. Royal Liverpool reads 133 to 537 nmol/L between 6am and 10am, and under 50 nmol/L at midnight, at every adult age.
Does cortisol increase with age?
Research suggests daily output rises and the curve from waking to evening flattens. A study of 185 adults aged 20 to 81 in Psychoneuroendocrinology reported both. The printed reference range does not change.
Is a cortisol of 210 nmol/L normal?
At 9am it sits in what Oxford University Hospitals calls the indeterminate band of 150 to 300, which may be normal. Later in the day it means something different again. The sample time is the missing half of that question.
What time should a cortisol blood test be taken?
Around 9am. Oxford University Hospitals states that a random non-9am cortisol is uninterpretable, and UK reference ranges are written for a morning window of roughly 6am to 10am.
What raises cortisol apart from stress?
Royal Liverpool names pregnancy and oral contraception alongside stress. Poor sleep, hard exercise and recent illness also move it. Steroid treatment makes the result uninterpretable.
Can a blood test show adrenal fatigue?
No. Adrenal fatigue is not a recognised diagnosis, so no marker reports it. A cortisol test measures the hormone at one moment, and a qualified clinician reads that alongside your history.
Related guides
Normal Cortisol Levels UK
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Cortisol Blood Test UK
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Cortisol and Sleep
The rhythm behind waking at 3am.
High Cortisol Symptoms UK
What people notice, and what the test adds.
Stress Blood Test UK
Which markers move when life does.
Blood Test Reference Ranges UK
Why normal on a lab report is a population range, not a target.