What is Lethargy?

Experiencing extreme fatigue, sluggishness, and low energy levels can indicate an underlying condition. You should see a doctor if you have been feeling lethargic for a long time. Although it is often short-lived and does not cause long-term damage, getting checked out for your health and safety is still important.

Lethargy Symptoms

Feeling lethargic is caused by a variety of factors. There are several common symptoms associated with lethargy, including:

  • Feeling exhausted

  • Anxiety

  • A lack of judgment or decision-making

  • Lack of energy

  • Being less alert

  • Dizziness

  • Muscle weakness

  • Headache

  • Slow reflexes

  • Irritability


If you cannot wake your baby or child, seek medical attention immediately.

What can Lethargy be a symptom of?

There are several reasons why you may feel lethargic:

Chronic Fatigue Syndrome

Chronic Fatigue Syndrome (CFS) is also called Myalgic Encephalomyelitis (ME), defined by extreme tiredness. The exact cause is not known. However, mental health issues, viruses, hormonal imbalances, or a combination of other factors may be the root of the problem.


The mental health condition depression may cause a person to feel fatigued and lack energy. This lack of energy can result from various factors, including difficulty sleeping, changes in appetite, and feeling overwhelmed by tasks.


Occasional anxiety is expected, but if you feel anxious regularly, it can lead to various physical and psychological symptoms, such as fatigue and lethargy.

Coeliac disease

Approximately one per cent of the population in the European Union is diagnosed with coeliac disease. This food intolerance is triggered when a person consumes gluten and can cause severe damage to the gastrointestinal system. Unfortunately, many people with coeliac disease go undiagnosed.


When you have Coeliac disease, you will likely experience lethargy, anaemia, weight loss and diarrhoea. To help manage this, a gluten-free diet is typically recommended.

Iron deficiency - anaemia

Those suffering from anaemia may experience feelings of fatigue, weakness, and low energy. Women who have heavy menstrual cycles or are pregnant are particularly affected by anaemia, but men can also be at risk of developing iron deficiency.


If you have a fever, you may experience symptoms such as extreme fatigue and tiredness. Once you can address the cause of the fever or it subsides on its own, you should begin to feel more energised.

Sleep apnoea

Sleep apnoea is a condition characterised by the narrowing of the airway while sleeping, leading to decreased oxygen levels in the blood. This can cause frequent awakenings at night, making a person tired the following day.


Chronic diseases such as diabetes can cause fatigue and exhaustion. People with undiagnosed diabetes may also experience other symptoms, such as sudden weight loss, increased thirst, and frequent urination. Managing diabetes daily can be challenging and can cause further fatigue.

Underactive thyroid

Lethargy, aching muscles and weight gain can be signs of an underactive thyroid gland, a more prevalent condition in women. Health complications can arise if the condition is left untreated.

Carbon monoxide poisoning

Carbon monoxide is a dangerous, colourless, odourless gas that can cause serious health problems. If you believe you may have been exposed to hazardous levels of carbon monoxide, it is essential to seek medical help immediately. Drowsiness, confusion, and headaches may be signs of carbon monoxide poisoning and should not be ignored.

Glandular fever

Glandular fever is a virus that causes a range of symptoms, including fatigue, sore throat, fever, and swollen glands. The infection usually resolves within six weeks, but it can leave the person feeling worn out and exhausted for several months.

Seasonal Affective Disorder

During winter, if you feel unusually lethargic and depressed, you may suffer from Seasonal Affective Disorder (SAD). This is a type of depressive disorder that follows a seasonal pattern and can be triggered by the lack of sunlight and shorter days.

Restless legs

People with restless legs experience a strong urge to move their legs, often accompanied by uncomfortable sensations such as tingling, burning, or aching. These sensations can worsen at night, leading to difficulty sleeping and exhaustion during the day. In some cases, people may experience involuntary leg jerking or twitching.

Heart disease

Everyday tasks, such as climbing stairs, may become more complex and cause feelings of lethargy or exhaustion, which may be the first signs of heart disease.


Water deficiency can lead to fatigue and dehydration, which can be dangerous, especially in children. Consuming regular sips of water helps to flush out toxins and keep your body hydrated.

Lyme disease

If you think you may have been exposed to this tick-borne disease, it is essential to seek medical attention immediately. Common symptoms include the development of a rash and feeling unwell, accompanied by fatigue. Take your time - contact a doctor as soon as possible.


During the days leading up to a woman's menstrual cycle, she may experience PMS (premenstrual syndrome), which can cause fatigue and other physical and emotional changes.


If you feel lethargic and affect your daily life, you should seek medical advice. They can look into the cause of your lethargy and help you find the proper treatment.

How can Mobi Doctor help?

Mobi Doctor offers the convenience of consulting with a doctor online, from any device, and anytime you need it. Whether from the comfort of your home, during a break at work, or when you are out and about, you can talk to a doctor about your fatigue and receive advice regarding the best course of action to recover quickly.


Our doctors offer advice, diagnosis, and treatment for any lethargy you may be experiencing. They are available seven days a week and can be contacted at a time that works for you. Should it become necessary, our doctors can also send you to a specialist for further treatment.



Connect with one of our doctors at Mobi Doctor with the click of a button and receive the care you require.

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