Written by H P-Fraser


What is Lethargy?

Often described as a state of exhaustion, lethargy is the feeling of prolonged drowsiness, fatigue and overall lack of energy that can present mentally and
physically. Lethargy can be directly linked to a pre-existing condition or a response to someone’s lifestyle or habits.

Despite often being mistaken for tiredness, the symptoms of Lethargy are usually longer-lasting, and more acute and apparent. Unlike tiredness, lethargy cannot be easily cured by a good night’s sleep and may need further investigation to determine the cause. Fatigue and lethargy are used interchangeably and often carry similar symptoms.

What are the signs & symptoms of Lethargy?

Lethargy can present itself in various different ways and can vary depending on the person. The common symptoms of Lethargy are:

  • Decrease in energy
    • A decrease in energy may appear as not feeling able to carry out usual daily tasks due to physical or mental fatigue.
  • Change of mood
    • Change of mood can present as sudden mood swings – often becoming more irritable and a general feeling of being low.
  • Prolonged fatigue
    • Prolonged fatigue is a sense of tiredness that is long-lasting and does not go away overnight or after a good night’s rest.
  • Lack of motivation
    • Lack of motivation refers to the loss of desire to partake in daily tasks and activities that would usually provide enjoyment.
  • Confusion
    • Confusion is described as an inability to think or express clearly whilst in some cases losing the idea of usually basic facts such as names, dates, or a sense of time
  • Disorientation
    • Disorientation, similar to confusion, can refer to the feeling of being lost, physically or mentally with limited ability to process the surroundings.

Lethargy can have many different causes and varied symptoms that often cannot be quantifiably measured through specific tests as symptoms of lethargy frequently are described differently from person to person. With particular symptoms relating to lethargy, it is common practice to undergo other unrelated tests to exclude potentially more serious conditions.

When someone is fatigued, it can affect several of the body’s systems such as the lymphatic system. If the body isn’t functioning as efficiently as usual due to, for example; illness, the lymphatic system can become impaired, resulting in swelling and puffiness. This mainly presents in the face, arms and legs and can in itself cause lethargy and fatigue.

What are the common causes of Lethargy?

The causes of lethargy can vary depending on the person.

For some, it is due to a pre-diagnosed or underlying condition where extreme fatigue and exhaustion are common side effects.

For others, lethargy can develop as the body’s natural response to someone’s lifestyle such as lack of exercise, poor sleeping pattern, stress or poor mental health.

In recent years there have been many direct connections between a common cold, the flu and Lethargy. A high proportion of people have experienced the symptoms of lethargy either during or post developing a virus, and for some, it has been found to be a long-lasting side effect. Feelings of extreme exhaustion both physically and mentally were common with those who suffered from a cold or flu.

When the body is sick, it’s the lymphatic system’s job to fight and remove the waste products such as bacteria or viruses throughout the body. It does this by creating white blood cells which can detect these foreign bacteria, toxins and waste products and then tries to remove them by returning them back into the bloodstream.
When this system is overworked, the drainage of this fluid can become impaired causing swelling of the lymph nodes which in some cases can prolong the recovery period and cause longer-term symptoms such as fatigue, grogginess and lethargy.

Poor mental health and lethargy share common symptoms such as low mood, lack of energy and motivation and often become closely linked because of this.

How is Lethargy diagnosed?

Diagnosing Lethargy consists of talking through with a GP a full medical history, explaining the symptoms and any other recent changes to the body. By doing this, the GP may find a link with a pre-existing condition whereby symptoms such as lethargy are common, or other reasons as to why the current symptoms are present.

If no explanations are found, the GP may carry out a physical exam. This usually includes; muscle strength testing, balance testing and blood pressure will be recorded. Based on this, the GP will determine whether or not further tests such as blood and urine samples are required to rule out any chronic conditions.

Due to Lethargy being a subjective symptom, there is no specific testing to determine if someone is suffering from Lethargy so any tests used are to rule out other conditions.

What are the treatment options for Lethargy?

Due to the nature of the condition, lethargy does not have a specific medical treatment. Talking with a medical professional can help identify any potential causing factors therefore can tailor specific advice based on this.
If the lethargy was diagnosed because of an underlying medical condition then the treatment will be tailored for that condition specifically.
If there were no other explanations for these symptoms then looking at making changes to daily routines or habits may be suggested.
Having those healthier lifestyle habits can make a significant difference both physically and mentally which in turn can reduce the symptoms of lethargy.

Examples of healthy lifestyle habits include:

  • Consistent hydration
    • Hydration helps maximize the blood and lymph flow around the body and increases overall energy
  • Regular exercise
    • Exercise is vital for overall well-being and helps pump lymph flow around the body, reducing fluid retention
  • Routine sleeping pattern
    • Maintaining a regular sleeping pattern allows the body to create a natural circadian rhythm and boosts energy levels
  • Looking after your mental health
    • Focusing on your mental health is as important as physical health and promotes overall wellbeing
  • Reducing alcohol and caffeine
    • Reducing the amount of caffeine and alcohol has profound positive effects on sleep, mood and regulates the body’s blood sugar levels

How long does Lethargy last?

The duration of lethargy symptoms very much depends on the cause. In some cases where Lethargy is due to a pre-existing condition, the symptoms may be longer lasting. If the cause is not because of a diagnosed condition, and more because of changes in habits then the effects of lethargy can be simpler to reduce.

Can Lethargy be prevented?

Due to the wide range of factors that can cause lethargy, it is important to be aware of lifestyle changes or habits. If someone has experienced lethargy before, being able to identify the factors which caused this will help prevent the future risk of developing Lethargy.

Regular exercise is vital for overall health but in particular, the lymphatic system which when compromised, can cause symptoms of lethargy. Unlike the heart for the bloodstream, the lymphatic flow doesn’t have a central pump system. It relies on other factors to help push the fluid around the body. The main example of this would be muscle contraction. When the muscles contract, it creates a pump-like mechanism, allowing more fluid to flow around the body at a faster, more efficient rate.

A large majority of the lymphatic system is made up of water, therefore, keeping hydrated increases the overall function of the lymph flow, helps to prevent blockages and increases overall energy throughout the body.

Reducing caffeine and alcohol can have profound effects on sleep, energy levels and overall function of the body all of which can help prevent symptoms of lethargy developing. Despite lethargy being longer lasting than tiredness, and not cured by one night’s rest, a regular sleeping pattern allows the body to recover and restore its energy.

Do I need to go to the GP or visit my local hospital?

Lethargy alone does not usually require any medical intervention however if combined with any other unusual symptoms then contact your GP for help advice as this may be a sign of a more serious condition. Additionally, if your symptoms change suddenly or chest pain, nausea, increased heart rate, numbness or disorientation occur then please seek immediate medical attention.


Lethargy feels like prolonged fatigue, low energy or lack of motivation for day-to-day activities.
Usually a side effect of other conditions, but can be caused by lack of exercise, overcoming a virus, poor mental health, or impaired lymphatic system.

Feeling extremely fatigued for a long period of time.

There is no specific disease that causes lethargy but can be a side effect of other conditions.
Lethargy itself isn’t dangerous but if you have any concerns or change of symptoms then speak to a GP.
Changing lifestyle habits such as regular exercise, keeping hydrated, looking after your mental health, and getting a constant sleeping pattern in place can help to reduce the effects of lethargy.
Lethargy and fatigue are often used to refer to similar symptoms. Both are longer lasting than tiredness, they can be used interchangeably to explain the symptoms.
If you have any concerns about lethargy, or notice a change in your symptoms then speak to a GP to eliminate any other potential factors for lethargy symptoms.
This may be due to a pre-existing condition whereby lethargy symptoms can be a side effect, or a change in lifestyle habits such as sleeping patterns, lack of exercise, and increased intake of caffeine or alcohol.
Mental health issues are linked with lethargy and in some cases can cause lethargic symptoms such as lack of motivation, change of mood, confusion and delusions.