What Is the Main Cause of Lethargy?

Legarthy or laziness coupled with fatigue, can be a symptom of sleep disorders, cancer treatment or a host of other conditions.

Lethargy is a lack of energy, sluggishness, apathy or indifference, or laziness.

What Are Symptoms of Lethargy?

Lethargy is a symptom of other medical conditions. Characteristics of lethargy may include:

• Lack of energy
• Sluggishness
• Listlessness
• Apathy or indifference
• Laziness
• Drowsiness
• Fatigue
• Tiredness

Many conditions can cause lethargy, from a simple lack of sleep to cancer treatments to side effects of medications. Some of the most common causes of lethargy include:

• Sleep disorders
  • Sleep apnea, in which people stop breathing for short periods during sleep
  • Restless leg syndrome, in which people have an uncontrollable urge to move their legs, often during the night
  • Insomnia
• Hormone imbalances
  • Underactive thyroid gland (hypothyroidism)
• Mental health conditions
  • Depression
  • Anxiety
• Cancer treatments
  • Chemotherapy
  • Radiation Therapy
• Infections 
  • Bacteria
  • Viruses
  • Fungus
  • Parasites
• Chronic fatigue syndrome (also known as myalgic encephalomyelitis, or ME) 
• Celiac disease, an autoimmune condition in which the immune system reacts to gluten
• Anemia (iron deficiency)
• Diabetes
• Certain medications 
• Muscle disease
• Pain and injury
• Surgery
• Over-exertion/too much exercise

This is not a complete list of all the conditions that can cause lethargy. Discuss your symptoms with your doctor. 

Treatment for lethargy depends on the underlying cause. 

It may include medication, lifestyle changes, or changing medications. Do not stop taking any medication without first talking to your doctor. 

In some cases, such as lethargy that follows surgery or injury, the lethargy may go away on its own once the body heals. 

Some causes of lethargy may be preventable. If lethargy is due to:

• Lack of sleep: Getting adequate rest may help
• Iron deficiency: Iron supplementation may prevent its recurrence
• Celiac disease: Avoiding gluten may relieve symptoms
• Diabetes: Managing blood sugar may prevent it
• Over-exertion/too much exercise: Cutting back on activity may relieve symptoms