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The Difference Between Tiredness and Fatigue: When It's Serious

Struggling with tiredness and fatigue? These complaints are more common than you might think. We often dismiss feeling tired, or try to bury it with caffeine or sugar. But ignoring or avoiding this feeling is not the way to make it go away. The truth is that these two are not the same. Tiredness is a natural response to a busy life. But fatigue is another story and can be a sign of a bigger problem. Before you dismiss your lack of energy, here’s what it could mean, and why you should talk to your doctor about it.

What’s the Difference Between Tiredness and Fatigue?

An image of a woman sitting on the floor holding her templesThey sound similar, but there’s actually a big difference between tiredness and fatigue. Tiredness is a normal response to a busy day. You can alleviate it with rest, sleep, and sometimes a good meal. You may feel tired at the end of a long day. But after an evening of relaxing, you should feel back to normal in the morning.

When you feel tired all the time, over a long period, and you can't relieve it by resting, then you have fatigue. Unfortunately, this is becoming a common experience for far too many people. There are a lot of different things that can bring on fatigue, many of them are things you should talk to your doctor about.

Medical Conditions That Cause Fatigue

The biggest danger of not knowing the difference between tiredness and fatigue is the fact that people often dismiss this symptom. They often see it as a natural reaction to the busyness of modern life. But fatigue can be a sign from your body that something has gone wrong.

Here are some serious health conditions that can cause fatigue, and why you should talk to your doctor about them if your energy levels remain low:

Mood Disorders

Mood disorders like depression and anxiety are both strongly associated with fatigue. Depression in particular causes intense fatigue that’s associated with sadness and sleep disruptions. And when you have anxiety, the constant feelings of alertness and worry can be exhausting and disrupt your sleeping patterns.

If you have anxiety or depression, it's important to see a doctor who understands these conditions and can provide helpful suggestions. Improving your mood will not only help restore your quality of life, but it will also help improve your energy levels.


Anemia is probably one of the most well recognized and understood conditions associated with fatigue. When you have anemia, you have low levels of iron in your blood. And because iron carries oxygen, this can leave you feeling exhausted and achy.

Anemia is strongly associated with women, because of the demands of menstruation and pregnancy, but it can also affect men and postmenopausal women as well.

Too much iron, a condition known as iron-overload disorder (hemochromatosis), is also strongly associated with fatigue. This condition is fairly rare and affects both women and men between the ages of 30 and 60.


Feeling tired along with poor healing and frequent urination are key symptoms of both type I and type II diabetes. If you have this condition, it’s important that you get it under control or it could lead to coma or even death, so see your doctor immediately.

Sleep Apnea

Sleep apnea causes your throat to close or narrow during sleep. This interrupts your breathing and causes snoring and dangerous drops in your blood oxygen levels. When you have sleep apnea you may find yourself waking up constantly during the night and feeling exhausted during the day. More men than women have sleep apnea and it can be caused by a variety of factors.

Celiac Disease

An image of the lining of the intestinesCeliac disease is a type of autoimmune disease that causes people to react to gluten. Gluten is a protein that’s found in wheat products and other grains, often in pasta, cake, cereals, and bread. When people with this condition eat these foods, their immune system reacts, causing symptoms like bloating, diarrhea, anemia, and fatigue.

This is obviously a very uncomfortable condition and yet many people don’t even know they have it. It’s easily diagnosed through a blood test, so ask your doctor about it if you’re concerned.

Gluten allergies are also a possibility. And even if you don't have a gluten allergy, you might still have gluten intolerance and sensitivity that causes leaky gut. This also increases your risk for autoimmune issues. So, if you find yourself having more symptoms of fatigue or tiredness especially after eating gluten, it might be wise to cut it out.

Underactive Thyroid

When your thyroid is underactive, it produces too little of the thyroid hormone known as thyroxine. This causes fatigue along with aches and pains, dry skin, and weight gain. There are a lot of different issues that can cause an underactive thyroid, and it’s more common in older women.

Chronic Fatigue Syndrome

Chronic Fatigue Syndrome or Myalgic Encephalomyelitis (ME) is a complicated disorder that occurs mostly in women. It causes severe fatigue that goes on for several months as well as other symptoms like sleep abnormalities and pain.

At this stage, the cause of this disorder is unknown, though researchers suspect that genetic or environmental factors may be involved. Many times, adrenal fatigue is misdiagnosed as chronic fatigue by conventional physicians.

Restless Legs Syndrome

Restless Legs Syndrome is an unusual condition that makes you want to move your legs. It usually occurs at night and can keep you awake. It can also cause discomfort or a crawling sensation in the legs and some people experience spontaneous leg jerking throughout the night.

This condition can be very disruptive to your sleeping patterns. And disturbed sleep means that you’ll feel fatigued all the time.

Chronic Stealth Infection

Tiredness and fatigue are strongly associated with chronic stealth infections, whether it's from EBV, CMV, Lyme, candida, parasites, or something else. These are infections that can cause fever, fatigue, swollen glands, a sore throat, joint aching, and/or sugar imbalance, depending on the type of infection. The acute symptoms usually go away within 4 to 6 weeks, but the fatigue can last for much longer than that.

What Should You Do for Tiredness and Fatigue?

There are several ways that you can try to address tiredness and fatigue. First of all, you need to become more aware of your energy levels. If you feel tired at the end of a long day but find that you feel better once you get up, then what you’re feeling is probably simple tiredness. You may simply have to adjust your daily schedule to have more rest periods or nutritious meals, for example.

A fatigue patient talking to a doctorHowever, if the tiredness lingers, then you may be experiencing fatigue, and you should see your doctor. They will be able to perform a medical test to search for common conditions that cause fatigue. They may also be able to offer suggestions to help you overcome this condition.

If you visit your doctor and still can’t get any answers or find a solution to your fatigue, then you may want to talk to someone about Adrenal Fatigue Syndrome (AFS). This condition is strongly associated with fatigue, yet isn’t well understood or accepted by the medical establishment yet. So, you may have to do some hunting around to find someone who understands and can help if you have this disorder.

How AFS Causes Fatigue

Both tiredness and fatigue are strongly associated with AFS. AFS can occur when you’re stressed over a prolonged period and the adrenal glands become fatigued and start to malfunction.

The adrenal glands are responsible for producing the stress hormone cortisol. This hormone is an essential part of your body’s NeuroEndoMetabolic (NEM) stress response, a set of six circuits of related organs and systems. During stressful periods, the NEM stress response activates, and cortisol is released from the adrenals. The cortisol causes changes in the body that are essential for helping you cope with stress.

However, these changes are supposed to be short-term. Unfortunately, because the modern world is filled with stressors, the NEM stress response in many people remains active. Cortisol levels stay high, and the body remains in a state of constant alert. This is a very damaging state. When it continues for too long, the adrenal glands can start to struggle to produce cortisol at the levels that the body is demanding. They can even start to become dysfunctional. And the body’s circuits, as well as the organs and systems within them, can also become dysfunctional.

Because so many different systems are involved in stress, this can be a very complicated condition. And because of the lack of understanding in conventional medicine, many sufferers experience it for a long time before they can find help and relief.

How Hormonal Circuit Dysfunction Causes Tiredness and Fatigue

In AFS, feelings of tiredness and fatigue are often strongly associated with Hormonal Circuit imbalances. The Hormonal Circuit includes the adrenal glands, so it’s usually quick to become involved when you have AFS. This circuit also includes the thyroid and the reproductive system, or the testicles in men and the ovaries in women.

This is known as the ovarian-adrenal-thyroid (OAT) axis and as it becomes unbalanced, one component of it usually becomes more problematic than the others. It’s often this component that becomes weaker, making it clinically dominant and the most trouble.

Additionally, these 3 components are strongly intertwined, so as one becomes weaker and clinically dominant, the others do as well. This affects not only the functioning of the Hormonal Circuit as a whole, but also how the individual components carry out their usual functions, often causing symptoms and conditions.

These types of malfunctions in the Hormonal Circuit can contribute to feelings of tiredness and fatigue. They can also bring on other conditions that cause fatigue. Here’s how:

The Adrenal Glands

An image of a kidney and adrenal glandAs the adrenal glands become dysfunctional because of AFS, hormone levels in the body become unbalanced. The adrenal glands are responsible for releasing more than 50 hormones into the body including cortisol, so this can cause widespread health problems.

Fluctuating cortisol levels that occur as a result of adrenal gland dysfunction are also associated with fatigue-related health problems. High cortisol levels can cause:

  • High glucose levels
  • Diabetes
  • Obesity
  • Muscle weakness

And when cortisol levels are low because of AFS, they’re associated with fatigue-related issues like:

  • Low blood pressure
  • Weak muscles
  • Decreased appetite

When the adrenal glands are the weakest component, it can also bring on mood instabilities that worsen fatigue.


When the thyroid is weaker than the other components and clinically dominant, it can cause severe fatigue as well as classical signs of low thyroid function.

As adrenal function decreases, thyroid function does the same. This naturally causes fatigue as well as low body temperature. It can also cause your thyroid to become clinically underactive, a condition known as hypothyroidism which can bring on severe and long-lasting fatigue.

It may also cause the opposite problem, where the thyroid becomes overactive because of imbalances. The overactive thyroid can bring on anxiety, which is also associated with fatigue.

Reproductive Organs

And as the body becomes fatigued, the reproductive system slows as well because reproduction isn’t an essential function during stressful times. This affects reproductive hormone levels, often causing estrogen dominance and problems with menstruation in women. It also affects hormone levels in men.

When the reproductive organs are clinically the weakest, it usually brings on memory loss and brain fog.

Overcoming Fatigue Caused by AFS

AFS is a complicated disorder. Many people who go to the doctor with this disorder often find themselves dismissed or given medications that treat the most obvious symptoms. Both of these outcomes just put additional stress on the body rather than helping to correct the underlying imbalances.

If you have severe fatigue as a result of AFS, it’s important that you see a clinician who’s aware of this disorder. They will be able to design a recovery plan that helps to rebalance the body’s circuits and lessen your stress levels overall, encouraging your body to return to a more natural state of functioning so that it can heal.

The Takeaway

Do you struggle with tiredness and fatigue? These issues aren’t always as benign as they seem. If you still feel exhausted after rest and a good night's sleep, you have fatigue. And this can be quite serious and a sign that you need to see your doctor. Here’s what to do if you’re concerned about feeling tired all the time:

  1. Track your energy levels to see if the tiredness eases when you rest or not.
  2. Take a look at your lifestyle to see if anything has changed that could be causing your tiredness.
  3. See your doctor about ongoing fatigue.

For help with fatigue and other troubling but non-specific symptoms, talk to our team on +1 (626) 571-1234 or click here.

© Copyright 2022 Michael Lam, M.D. All Rights Reserved.

Dr. Lam’s Key Question

The difference between tiredness and fatigue is a matter of degrees. Tiredness is a temporary experience that’s relieved by rest and sleep. Fatigue is the kind of tiredness that drags on and doesn’t stop, no matter how much you rest. And it can mean you need to see a doctor.

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