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Normal Cortisol Levels By Age: Why It Might Not Matter

Written by Dr. Michael Ruscio, DC on February 24, 2025

Written by Dr. Michael Ruscio, DC on February 24, 2025 — Reviewed by Hilary Watts

• Cortisol|
• Normal Levels|
• DUTCH Test|
• Adrenal Fatigue|
• Tests Don’t Help|
• Improve Fatigue|

If you’re feeling fatigued on a regular basis, it’s possible that your cortisol levels are off balance.

Although many functional medicine practitioners would start by testing your cortisol levels and treating the test results, we haven’t used cortisol tests like the DUTCH adrenal test at our clinic for some time.

Why? Because for most cases of persistent fatigue, these tests don’t offer actionable insights that would alter our natural treatment approaches.

That said, there are a couple of medical conditions where cortisol concentrations are either very high or very low, and testing is a necessary part of diagnosis.

Let’s investigate normal cortisol levels by age and when checking your cortisol level is and isn’t necessary.

What Is Cortisol and What Does It Do?

Cortisol is a glucocorticoid (type of steroid) hormone that regulates the stress response, metabolism, and immune system activity. It is produced by the adrenal glands when the hypothalamic-pituitary-adrenal (HPA) axis gives the go signal. In a nutshell, here’s how the HPA axis works 1:

1. Under stress, the hypothalamus in the brain produces corticotropin-releasing hormone (CRH).
2. CRH tells the brain’s pituitary gland to release adrenocorticotropic hormone (ACTH).
3. ACTH stimulates the adrenal glands to make and secrete cortisol.
4. Higher cortisol production and increasing levels of cortisol in the blood then signal the hypothalamus and pituitary gland to reduce CRH and ACTH production.
5. This change puts the brakes on cortisol production until it’s needed again.

In healthy individuals, blood cortisol levels follow a circadian rhythm, peaking in the morning upon waking, and decreasing gradually throughout the day. Additionally, cortisol levels can spike in response to daily stressors. 

A flattened cortisol curve (where the level doesn’t rise upon waking and follow the normal downward curve through the day) has been associated with immune and inflammatory issues, fatigue, obesity, and depression 2. Flattened cortisol levels with abnormal daily or diurnal variation that then spike in the evening have been associated with insomnia and other sleep disturbances 3.

However, observational research showing such associations doesn’t prove cause and effect. That means we don’t know whether the symptoms or abnormal cortisol levels come first, or if the symptoms are related to cortisol at all 2.

Normal Cortisol Levels by Age

If your doctor suspects that you have an endocrine condition affecting your level of cortisol or cortisol secretion, they will likely order an FDA-approved test, also known as an assay. The test will require urine, saliva, or a blood sample to measure your cortisol at different points throughout the day.

What counts as a healthy cortisol level generally changes throughout a person’s lifespan. Levels increase in adolescence and throughout adulthood, tending to be highest in older females 4.

Elevated levels of cortisol at any age are associated with higher levels of psychosocial stress, poorer cognitive performance, and shrinking memory-related structures in the brain, such as the hippocampus 4.

Two medical conditions that cortisol testing can diagnose are Cushing’s syndrome and Addison’s disease. Both are more common in midlife (ages 30–50) and reflected by cortisol levels that are highly abnormal, not just a little off-kilter.

High Cortisol Symptoms

Cushing’s syndrome patients have very high levels of cortisol, usually resulting from taking too much corticosteroid medication, or from a growth on the pituitary or adrenal glands. High cortisol symptoms of Cushing’s include 1:

• Weight gain, especially in the face and abdomen
• Fatty deposits between shoulder blades
• Diabetes
• High blood pressure
• Hirsutism (unwanted hair growth) in women
• Muscle weakness
• Osteoporosis

Low Cortisol Symptoms

Addison’s disease is a condition of very low cortisol levels that typically occurs because of an autoimmune attack on the adrenal glands. Symptoms of this disease of adrenal insufficiency include 1:

• Fatigue 
• Weight loss 
• Low blood pressure 
• Dark spots on the skin (known as hyperpigmentation)
• High blood potassium levels and low sodium

It’s important to work with a healthcare provider to interpret your cortisol test results. Whatever your age, factors like pregnancy and estrogen therapies (including oral contraceptives) can cause your cortisol to read higher than normal but still be ok 5 6.

DUTCH Testing for Fatigue

The DUTCH (Dried Urine Test for Comprehensive Hormones) has gained popularity within the functional and integrative health communities for assessing fatigue conditions. For the DUTCH Adrenal test by Precision Analytical, you pee on filter paper at specific times throughout the day and let the samples dry completely. A lab then analyzes the samples using a type of mass spectrometry, which is the gold standard of cortisol analysis.

The DUTCH test’s unique dried urine collection method is easier to use than conventional medical testing, and it measures hormone metabolites (byproducts) that standard tests may not detect 7.

While the DUTCH adrenal function test can provide accurate cortisol levels to help diagnose true cortisol-related diseases, this is not why most people use it. Many people turn to cortisol tests, like the DUTCH test, hoping for a biological explanation of symptoms like fatigue, brain fog, or depression. This is understandable when you’re always exhausted and seeking answers.

Unfortunately, cortisol testing is not helpful for evaluating fatigue and chronic stress conditions like burnout or the now-debunked concept of “adrenal fatigue” 8.

The Myth of “Adrenal Fatigue”

So-called adrenal fatigue—a term for tired adrenals and low cortisol levels related to chronic stress—has gained popularity as a condition that the DUTCH and other cortisol tests available on the internet can supposedly diagnose.

Although it sounds like a neat explanation for symptoms of exhaustion, adrenal fatigue (in the sense of the adrenal glands burning out), has not been proven. In fact, major medical organizations, like the Endocrinology Society, do not recognize adrenal fatigue as a legitimate condition, and research supports this stance.

For example, a systematic review of 58 studies found no scientific basis for linking adrenal impairment to non-specific symptoms like chronic fatigue. This was across studies that varied widely in their methods and biological markers. Over 60% of studies that measured cortisol levels from saliva taken four times over 24 hours found no differences between fatigued and energetic patients 8.

The systematic review also highlighted a glaring lack of formal criteria for defining and diagnosing “adrenal fatigue,” including what, when, and how often to test, what normal ranges are, and how reliable tests are.

Rather than trying to chase down a diagnosis of adrenal fatigue, it’s better to work with your doctor to find the real underlying reason for your symptoms. A few of the surprising reasons for fatigue include: 

• Gut conditions, such as IBS (irritable bowel syndrome), inflammatory bowel disease (IBD), and leaky gut 9 10
• Hypothyroidism (underactive thyroid) 11
• Chronic sleep issues 12
• Nutrient deficiencies 13 14 15 16
• Myalgic encephalomyelitis / chronic fatigue syndrome (ME/CFS) 17
• Burnout or exhaustion related to chronic stress 8 18

Why Cortisol Testing Is of Little Use

There’s likely a grain of truth in the observational research that suggests a link between disrupted cortisol release patterns and fatigue. However, this research is far too inconsistent and nonspecific to use it for interpreting cortisol test results.

Given this and the much stronger evidence that adrenal fatigue isn’t actually a valid condition, cortisol testing isn’t necessary for people of any age with persistent fatigue. 

To help save time, frustration, and money, I recommend that my clients with fatigue focus on overall lifestyle changes and stress management techniques rather than worrying about their cortisol. More often than not, the solution lies within simple diet and lifestyle changes.

3 Ways to Improve Fatigue 

Working with clients at the clinic, we’ve found that fatigue and disrupted cortisol responses often improve when we support blood sugar, gut health, and stress management, as follows.

1. Blood Sugar Control

One of cortisol’s jobs is to regulate blood sugar by offsetting the effect of insulin, a hormone the pancreas makes. Insulin’s main job is to reduce blood sugar.

But when you need blood sugar, cortisol can release glucose stored in the body and cause blood sugar to go up 1. As you might imagine, having high cortisol levels for too long can lead to chronically high blood sugar, which can cause type-2 diabetes.

Normalizing blood glucose (and thereby cortisol and insulin responses) with healthy eating can go a long way toward preventing or relieving fatigue. Simple ways to support healthy blood sugar levels include:

• Avoid high-glycemic foods (sugar and refined carbs that release sugar quickly).
• Experiment to find the right amount of fiber, starchy carbs, and healthy fats to meet your needs. I come across many people who think they need to go low-carb but actually have better energy levels when they include some healthy carbs, like whole grains and legumes.
• Eat an optimal amount of protein at each meal. For many people, this is around 30 grams per meal, starting with a high protein breakfast.

Another thing to be mindful of is accidental undereating, which is something I see a lot in busy people who get so caught up that they forget to sit down and eat a full meal.

Best Blood Sugar-Balancing Diet  

A healthy diet that is good at regulating blood sugar 19 and may help normalize cortisol is the Mediterranean diet 20. This diet is also known to improve microbiome health 21, which can indirectly support energy levels by improving nutrient absorption and blood sugar control. 

Other types of healthy eating can also work to stabilize blood sugar and thereby tackle fatigue. For example, we work with many clients who have food sensitivities and gut issues, like IBS or IBD, on top of fatigue symptoms. For these clients, a Paleo diet or a low-FODMAP diet is often more suitable.

2. Probiotics 

A clinical trial I covered in a podcast shed light on how probiotic therapy could help people manage the related issues of fatigue, stress, mental health, sleep quality, and gut health 22. 

The study involved women with or without IBS. The IBS patients tended to have similar anxiety, depression, and sleep quality to the healthy women. But unlike the other women, patients with worse IBS also had blunted cortisol levels when they woke up in the morning.

The IBS patients took a daily probiotic containing two strains of Bifidobacterium longum and had significant improvements in gut symptoms, anxiety, depression, and sleep quality, compared to before the probiotic. Those with blunted waking cortisol levels also had a normalized morning cortisol response after the probiotic.

This study explained how fatigue and worsened IBS symptoms are associated with psychosocial stress. Although they didn’t measure fatigue in particular, whatever fatigue the participants had almost certainly lessened with their other symptoms. That’s why for my clients with fatigue, we focus on gut health with diet and probiotics (ideally a multistrain product) and watch for improvements. This works better than testing cortisol levels and treating the results.

3. Lifestyle Changes

In addition to diet and probiotics, the following strategies can help manage chronic stress, which is often at the root of fatigue and abnormal cortisol patterns.

Exercise

Moderate exercise (zone 2 exercise), like brisk walking or easy cycling you can do while speaking in full sentences, is an excellent way to improve stress resilience. On a cellular level, it reduces pro-inflammatory chemicals and promotes anti-inflammatory ones 23. Adding a 10–30-minute daily walk to your current exercise schedule is a great way to go.

Mind-Body Therapies 

Meditation can reduce stress markers, including blood pressure and cortisol, for a wide range of people 24. Similarly, mindfulness-based stress reduction (MBSR) and cognitive behavioral therapy (CBT) can reduce salivary cortisol levels, helping people stay more calm during stressful tasks 25. 

Supplements

Some supplements (other than probiotics) that may have beneficial effects on fatigue, stress, and cortisol levels include:

• Omega-3 fatty acids 26
• Tangeretin 27
• Rhodiola extract 28
• Ashwagandha extract 29

It’s a good idea to talk to your doctor about which supplements and doses are best for you.

Treat—Don’t Test—Abnormal Cortisol

Regardless of your age, if you’re dealing with long-lasting fatigue, it’s often more effective to focus on holistic approaches rather than cortisol tests. Targeting upstream causes, like blood sugar swings, poor gut health, inactivity, and a lack of mental health support, can lead to better overall well-being, and cortisol levels will likely normalize in tandem.

For our clients with lingering fatigue, we often start with dietary changes and probiotics, and then coach them to incorporate stress reduction and management techniques. Adopting a similar strategy might be beneficial for you, but be sure to consult your doctor to determine the best approach for your specific needs.

Alternatively, you can reach out to one of our experienced practitioners or get more in-depth information on resetting your gut health from my book, Healthy Gut, Healthy You.

The Ruscio Institute has developed a range of high-quality formulations to help our clients and audience. If you’re interested in learning more about these products, please click here. Note that there are many other options available, and we encourage you to research which products may be right for you. The information on DrRuscio.com is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment.