Brain & Nervous System Health Center

Many health problems cause confusion or decreased alertness. It is not unusual for a person who is sick to be sleepy or confused when he or she wakes up. But extreme sleepiness may be a symptom of a more serious health problem.

Confusion may range from mild to severe. Symptoms of confusion may include:

• Jumbled or disorganized thoughts.
• Unusual, bizarre, or aggressive behavior.
• Having trouble solving problems or doing tasks that used to be easy for you.
• Not knowing where you are or not recognizing family members or familiar items.
• Firmly held but false beliefs (delusions).
• Seeing, hearing, feeling, smelling, or tasting things that are not really there (hallucinations or illusions).
• Unfounded suspicions that others are after you or want to harm you (paranoia).

Decreased alertness occurs when a person is not fully awake, aware of, or able to respond normally to his or her external environment. Decreased alertness may also mean that a chronic illness has gotten worse.

A sudden change in the mental state or level of consciousness may be caused by:

• A head injury. Serious head injuries may cause injuries to the brain.
• Decreased or blocked blood flow to the brain. This may occur during a transient ischemic attack (TIA) or a stroke.
• A seizure disorder (epilepsy).
• A disease, such as a brain tumor or problems from diabetes.
• Environmental factors, such as dehydration, cold temperature exposure (hypothermia), and heatstroke.
• Medicines and alcohol or drug abuse or withdrawal.
• Infection, especially an infection of the nervous system.
• Shock that is caused by infection that has spread throughout the blood and tissues (sepsis).
• Heart problems, such as a heart attack, an irregular heart rhythm (arrhythmia), or heart failure.
• Thyroid problems, such as hyperthyroidism.
• Low oxygen levels from chronic obstructive pulmonary disease (COPD), pulmonary embolism (PE), or altitude sickness.
• Metabolism problems from liver or kidney failure.

Other problems that may lead to confusion or decreased alertness include:

• Decreased hearing or vision.
• Electrolyte imbalances, such as low levels of sodium and potassium in the blood.
• Low blood sugar (hypoglycemia) or high blood sugar (hyperglycemia).
• Malnutrition and vitamin deficiencies.
• Sleep problems, such as the inability to fall asleep or stay asleep (insomnia) or sleep apnea.

A complete medical examination may be needed before the cause of your confusion or decreased alertness can be diagnosed. Treatment depends on the cause of the problem. Contact your doctor for an exam if you are having problems with confusion or decreased alertness.