Lack of energy can be described as tiredness, weariness, lethargy or fatigue. It can be accompanied by depression, decreased motivation, or apathy. Lack of energy can be a normal response to inadequate sleep, overexertion, overworking, stress, lack of exercise, or boredom. When part of a normal response, lack of energy often resolves with rest, adequate sleep, stress management, and good nutrition.

Persistent lack of energy that does not resolve with self-care may be an indication of an underlying physical or psychological disorder. Common causes include allergies and asthma, anemia, cancer and its treatments, chronic pain, heart disease, infection, depression, eating disorders, grief, sleeping disorders, thyroid problems, medication side effects, alcohol use, or drug use.

Patterns and symptoms of lack of energy may help you discover its cause. If it starts in the morning and lasts all day, it could be due to lack of sleep or depression. If it develops as the day passes and is accompanied by dry skin, constipation, cold sensitivity, and weight gain, it may be caused by an underactive thyroid gland. The combination of shortness of breath and lack of energy could be due to heart or lung problems. The goal of a doctor’s evaluation is to identify the root cause(s) for the condition.

Persistent fatigue with no clear diagnosis may result from chronic fatigue syndrome, which can start with a flu-like illness and is often not relieved with rest. Other symptoms, such as cognitive difficulties, prolonged exhaustion and illness after activity, muscle or joint pain, sore throat, headache, and tender lymph nodes, are common.

Lack of energy by itself is rarely an emergency; however, if it develops suddenly or is accompanied by other serious symptoms, it may require immediate evaluation to avoid significant complications. Seek immediate medical care (call 911) for sudden energy loss, dizziness, chest pain or pressure, confusion, loss of vision or changes in vision, high fever (higher than 101 degrees Fahrenheit), sudden swelling or weight gain, shortness of breath, rapid heart rate (tachycardia), change in level of consciousness or alertness, severe pain, or if you think you might be a danger to yourself or others.

If your lack of energy is persistent or causes you concern, seek prompt medical care.

What other symptoms might occur with lack of energy?
Lack of energy may accompany other symptoms that vary depending on the underlying disease, disorder or condition. Lack of energy is a nonspecific symptom, so identifying other symptoms may be helpful in determining its cause.

Heart and lung symptoms that may occur along with lack of energy
Lack of energy may accompany other symptoms affecting the heart or lungs including:

Abnormal heart rhythms (arrhythmias)
Chest pain
Cough
Dizziness
Rapid heart rate (tachycardia)
Shortness of breath (worsens with exertion)
Wheezing (whistling sound made with breathing)
Other symptoms that may occur along with lack of energy
Lack of energy may accompany symptoms related to other body systems including:

Anxiety
Appetite changes
Change in bowel movements or diarrhea
Depressed mood
Feeling very thirsty
Fever
Frequent urination
Hair loss
Musculoskeletal pain
Nausea with or without vomiting
Skin changes
Unintentional weight gain or loss
Weakness (loss of strength)
Serious symptoms that might indicate a life-threatening condition
In some cases, lack of energy may be a symptom of a life-threatening condition that should be immediately evaluated in an emergency setting. Seek immediate medical care (call 911) if you, or someone you are with, have any of these life-threatening symptoms including:

Being a danger to oneself or others, including threatening, irrational, or suicidal behavior
Change in level of consciousness or alertness, such as passing out or unresponsiveness
Chest pain, chest tightness, chest pressure, palpitations
High fever (higher than 101 degrees Fahrenheit)
Not producing any urine
Rapid heart rate (tachycardia)
Respiratory or breathing problems, such as shortness of breath, difficulty breathing, labored breathing
Severe pain
Sudden change in vision
Sudden swelling or weight gain
Vomiting blood, rectal bleeding, or bloody stool
What causes lack of energy?
Lack of energy can be a normal response to inadequate sleep, overexertion, overworking, stress, lack of exercise, or boredom. When part of a normal response, lack of energy often resolves with rest, adequate sleep, stress management, and good nutrition. Persistent lack of energy that does not resolve with self-care may be due to a variety of diseases, disorders or conditions.

Heart and lung-related causes of lack of energy
Lack of energy may be caused by heart and lung problems including:

Asthma

Chronic obstructive pulmonary disease (COPD, includes emphysema and chronic bronchitis)

Coronary artery disease (plaque buildup in the walls of the coronary arteries)

Congestive heart failure (deterioration of the heart’s ability to pump blood)

Heart valve disease

Irregular heartbeat

Pneumonia

Psychosocial and neurological causes of lack of energy
Lack of energy may be caused by psychosocial or neurological conditions including:

Alcohol use

Anxiety disorders

Dementia

Depression

Drug abuse

Eating disorders

Grief

Overwork

Work shift changes

Other causes of lack of energy
Lack of energy can also be caused by diseases, disorders or conditions including:

Anemia (low red blood cell count)

Cancer and its treatment

Chronic fatigue syndrome

Chronic pain conditions

Diabetes (chronic disease that affects your body’s ability to use sugar for energy)

Kidney disease (includes any type of kidney problem, such as kidney stones, kidney failure and kidney anomalies) or liver disease (includes any type of liver problem, such as hepatitis, cirrhosis and liver failure)

Infections

Malnutrition

Medication side effects

Rheumatologic conditions, such as rheumatoid arthritis (chronic autoimmune disease characterized by joint inflammation), fibromyalgia (chronic condition that causes pain, stiffness and tenderness), and lupus

Sleep disorders

Thyroid disorders

Serious or life-threatening causes of lack of energy
In some cases, lack of energy may be a symptom of a serious or life-threatening condition that should be immediately evaluated in an emergency setting. These include:

Acute decompensated heart failure (rapid deterioration of the heart’s ability to pump blood)

Arrhythmia (abnormal heart rhythm)

Drug overdose

Electrolyte imbalances

Exposure to environmental toxin or poison

Hemorrhage or internal bleeding

Severe depression

Severe infection

Trauma

Questions for diagnosing the cause of lack of energy
To diagnose your condition, your doctor or licensed health care practitioner will ask you several questions related to your lack of energy including:

When did you first notice your lack of energy?

Are you getting sufficient sleep?

How often is lack of energy affecting you?

Do you have any stress in your life?

How is your mood?

What is your schedule like?

What is your diet like?

What kind of exercise do you get?

Do you have any other symptoms?

What medications are you taking?

Do you drink any alcohol?

Do you use any illicit drugs?

What are the potential complications of lack of energy?
Because lack of energy can be due to serious diseases, failure to seek treatment can result in serious complications and permanent damage. Once the underlying cause is diagnosed, it is important for you to follow the treatment plan that you and your health care professional design specifically for you to reduce the risk of potential complications including:

Accidental trauma

Chronic pain

Depression

Disability

Isolation

Progressive heart, lung, liver or kidney disease

Spread of cancer

Spread of infection