Fatigue: When Is It a Symptom of a Serious Medical Condition

Fatigue is a word used to describe feelings of overwhelming tiredness. When you are fatigued, you lack the energy or the motivation to do even the simplest tasks. You might feel drowsy or sleepy, but being sleepy alone does not equal being fatigued.

Most of the time, fatigue comes after a series of strenuous activity. People who do not eat a balanced diet and, therefore, not getting enough macronutrients the body needs may complain of fatigue. A lack of exercise also causes fatigue.

However, if you are making lifestyle choices that are considered healthy yet still feel fatigued, you might have an underlying medical condition. You would need to see a doctor to receive a diagnosis and proper treatment to address the problem that is causing fatigue.

Hypothyroidism and Hyperthyroidism

Fatigue is one of the most common thyroid symptoms. If your thyroid is not working as it should be, then you likely will feel extreme tiredness that cannot be resolved with rest.

Both hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid) cause fatigue.

Your thyroid, which is located near the base of your neck, is responsible for releasing the two hormones that regulate your metabolism. Hormones T-3 and T-4 can also influence your heartbeat, your breathing, your body temperature, your cholesterol levels, your menstrual cycles if you are a woman, and whether you gain or lose weight.

Sometimes, the thyroid develops a problem that pushes it to release too much or too little hormones.

It might be hypothyroidism if fatigue is accompanied by weight gain, an elevated level of cholesterol, constipation, muscle aches and weakness, pain and stiffness of joints, hoarseness of voice, increased sensitivity to cold, slower heart rate, and depression. If you experience fatigue along with unintentional and sudden weight loss, rapid or irregular heartbeat, sweating, tremor, more frequent bowel movements, and nervousness and anxiety, it can be caused by hyperthyroidism.

If your doctor suspects either hypothyroidism or hyperthyroidism, they will request a blood test to measure the amount of thyroid-stimulating hormone present in your body.


Fatigue can also be a symptom of type 1 and type 2 diabetes. When you have diabetes, the level of blood sugar (also known as glucose) in your body is too high.

Your pancreas produces insulin, the hormone that helps the glucose that comes from the food you eat to get into cells to be transformed into energy. When your body does not create enough insulin or cannot use insulin well, the glucose from the food you eat stays in the blood.

Other symptoms of diabetes include frequent urination, increased thirst, increased hunger, blurred vision, slow-healing sores and wounds, and frequent infections.

A blood test is needed to check your blood sugar level and determine whether you have diabetes or not.


Fatigue can be a symptom of a mental health problem, too.

Patients who have been diagnosed with depression might feel tired all the time. That is because, when a person is depressed, their body might not be releasing the right amount of hormones that regulate mood, motivation, pleasure, and energy levels.

Depression also causes sleep problems and interfere with eating food and exercising. These things will exacerbate fatigue.

Everyday fatigue can look like depression and vice versa. To diagnose whether you have a mental health problem, you should see a mental health professional.

woman holding her head in her hands

Chronic Fatigue Syndrome

Chronic fatigue syndrome (CFS), also known as myalgic encephalomyelitis (ME), is characterized by extreme tiredness or generally feeling unwell. It can affect anyone, but it is more common among women in their mid-20s up to mid-40s.

CFS/ME can look like a symptom of other medical conditions, but it is not caused by any illness. What causes CFS/ME is still unknown, but experts believe that a previous viral infection, psychological stress, or a combination of multiple other factors can lead to extreme tiredness.

People who have undiagnosed CFS/ME can also experience headaches, sore throat, sore glands, flu-like symptoms, fast/irregular heartbeat, muscle and joint pain, dizziness, sleep problems, and difficulty concentrating, thinking, or remembering.

Diagnosing CFS/ME is not easy. The doctor needs to rule out all possible medical conditions that might be causing extreme tiredness.

There is also no one way to treat CFS/ME. The patient can be prescribed medication to manage pain and sleeping problems. The doctor can also recommend an exercise program called GET (graded exercise therapy).

CFS/ME can improve over time, but some patients never fully recover from it.

Fatigue is a pretty common experience, especially among adults. However, it should not be ignored. If it happens frequently and without any immediate apparent cause, you should see a doctor to diagnose and treat any underlying medical condition.

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