Symptoms and what sits behind them
Low Cortisol Symptoms: The Signs Worth Checking
Reviewed by a qualified clinician · analysed at UKAS-accredited UK labs (ISO 15189)
Last reviewed August 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.
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Low cortisol tends to show up as deep tiredness that rest does not fix, dizziness when you stand, salt cravings, weight loss, nausea and low mood. It is uncommon. A morning blood test shows where your level sits, and a GP confirms the cause.
You are tired in a way that sleep does not touch. You stand up and the room tilts. You have started salting your food twice. Alone, each of those is nothing. Together, they are a pattern worth looking at.
Cortisol is the hormone that gets you going in the morning and holds your blood pressure and blood sugar steady through the day. Most articles are about having too much of it. Running low is rarer, and it feels very different.
By the Helvy Medical Team · Reviewed by a qualified clinician · 6 min read
1. What does low cortisol feel like?
No single symptom means much on its own. The cluster is what counts. The NHS lists these as early signs when the adrenal glands are not producing enough:
The tiredness is the part people describe most. It is not the wired-but-tired feeling of high cortisol. It is flat. Mornings are the worst part of the day, and a good night makes little difference.
2. Why is low cortisol so often missed?
Because every symptom on that list belongs to a dozen other things. Tiredness, low mood and poor concentration also fit an underactive thyroid, low iron, low B12 and plain burnout.
“A major problem with identifying people with AD is the non-specific nature of many of the presenting symptoms.”
— British Journal of General Practice, on Addison's disease in primary care
The same paper reports that 60% of patients have seen two or more clinicians before the diagnosis is even considered. That is not a failure of care. It is what happens when vague symptoms meet a condition that affects roughly 1 in 10,000 people in the UK.
It also means the common explanations deserve ruling in or out first. A full blood count and a thyroid check are usually where a GP starts, and they answer the question far more often than cortisol does.
3. What makes cortisol run low?
By far the most common reason is steroid medicine. Taking steroids for weeks or months tells the body to ease off making its own cortisol, and that dial takes time to turn back up after you stop.
A review of the evidence in the Journal of Clinical Endocrinology and Metabolism found the risk climbs with dose and duration. It ran from 2.4% on low doses up to 21.5% on high ones, and from 1.4% after 28 days of treatment to 27.4% after a year. Inhaled steroids for asthma sat at 6.8%. Never stop a prescribed steroid on your own. That is a conversation for the prescriber.
The other causes are rarer. The adrenal glands themselves can stop working properly, which is Addison's disease. The pituitary gland, which sends the signal, can also be the problem. Both need a GP.
One thing worth naming: “adrenal fatigue” is not a recognised medical diagnosis, and a review of 58 studies found no evidence for it. The exhaustion behind the search is real all the same. Our guide on adrenal fatigue and what to test instead covers what does explain it.
4. When to see a GP straight away
Some of this needs urgent medical help rather than a blood test you order yourself. Contact 111, or 999 if it is severe, for any of the signs the NHS links to an adrenal crisis:
This matters more if you take steroids, or have recently come off them. Illness raises the body's cortisol needs, and that is when a shortfall shows itself.
5. How to check where your level sits
Timing decides the number. Cortisol peaks within an hour of waking and falls all day. Take the sample in the morning, before 10am, fasting and before caffeine. An afternoon reading looks low even when nothing is wrong, and people scare themselves that way.
Be clear on what a blood cortisol does. It measures the level in that sample. It does not settle the cause. If a reading comes back low, the next step sits with your GP, who can arrange a Synacthen test that checks how the adrenal glands respond to a signal.
One number is also thin on its own. Reading cortisol alongside TSH, vitamin D and B12 is what separates a cortisol question from the look-alikes.
Our General Energy & Wellness panel (£149) measures cortisol alongside thyroid, vitamin D, B12, magnesium and 12 more markers from a home finger-prick sample. It is information to discuss with a qualified clinician, not a diagnosis. More on timing and ranges in our cortisol blood test guide, and on the wider picture in the energy and fatigue hub.
Frequently asked questions
What are the first signs of low cortisol?
Usually deep tiredness that sleep does not fix, dizziness on standing, salt cravings and a fading appetite. Weight loss, nausea and low mood often follow. The signs build slowly over months, which is part of why they get missed.
Can stress cause low cortisol?
Not in the way the internet suggests. Long stress usually pushes cortisol up, not down. The idea that stress wears the adrenal glands out is the “adrenal fatigue” theory, and the evidence does not support it. Real shortfalls have other causes.
Can steroid inhalers or tablets lower cortisol?
Yes, and this is the most common cause. Risk rises with dose and length of treatment. A pooled review found 6.8% for inhaled steroids in asthma, and 27.4% after a year of treatment. Speak to your prescriber rather than stopping anything yourself.
What time should a cortisol blood test be taken?
In the morning, before 10am, fasting, with no caffeine or hard exercise first. Cortisol peaks shortly after waking and drops through the day. A sample taken later reads low for reasons that have nothing to do with your health.
Does a low cortisol result mean I have Addison's disease?
No. A single reading does not establish a cause. Addison's is rare, at roughly 1 in 10,000 people in the UK, and sample timing alone can pull a number down. Take a low result to your GP, who can arrange the test that answers it properly.
Can a finger-prick sample measure cortisol?
Yes, when a UKAS-accredited UK laboratory processes it. Timing is the thing that decides whether the number is worth reading. Morning, fasting, before caffeine, and note the time when you register your kit.
Stop guessing at the tiredness
Our General Energy & Wellness panel (£149) measures cortisol alongside thyroid, vitamin D, B12 and 13 more markers, so you see the stress hormone in context. Home finger-prick kit, results usually within 5 working days of the lab receiving your sample, from UKAS-accredited UK laboratories.
Medical disclaimer: This content is for informational purposes only and does not constitute medical advice, diagnosis, or treatment. Studies cited in this guide describe group averages and may not apply to your individual situation. Do not make changes to medication, supplementation, or treatment plans based solely on information in this article. Never stop a prescribed steroid without speaking to your prescriber. Consult your GP or a qualified healthcare professional. All Helvy blood tests are processed by UKAS-accredited UK laboratories to ISO 15189.
Last updated: August 2026 · By Helvy · Medically analysed at UKAS-accredited UK laboratories
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