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Blackouts - Causes


Healthgrades Editorial Staff

What causes blackouts?

Blackouts may arise from a variety of conditions or events that affect the brain. Often, blackouts will result from a traumatic event or an event that involves head injury.

Traumatic causes of blackouts

Blackouts may often be caused by trauma to the head or brain including:

  • Complications of brain surgery
  • Concussion
  • Electroshock therapy
  • Injections and innoculations
  • Mild head injury
  • Phlebotomy (drawing a blood sample)
  • Traumatic emotional event

    Substance-related causes of blackouts

    Blackouts can also be caused by a variety of drugs and other substances including:

    • Alcohol intoxication

    • Medication side effects, such as the side effects of cancer treatments or seizure medications, or agents used for anesthesia

    • Poisons, such as cleaning chemicals or pesticides

    • Recreational drug use

    Disease and disorder causes of blackouts

    Blackouts can be caused by different diseases and disorders including:

    • Anemia

    • Brain or spinal cord injury or tumor

    • Cardiac arrhythmia

    • Dehydration (loss of fluids and electrolytes, which can be life threatening when severe and untreated)

    • Dementia

    • Depression

    • Encephalitis (inflammation and swelling of the brain due to a viral infection or other causes)

    • Epilepsy (disorder characterized by recurrent seizures)

    • Infections of the brain

    • Nutrient deficiency

    • Parkinson’s disease (brain disorder that impairs movement and coordination)

    • Postural hypotension

    • Vasovagal syncope

    Serious or life-threatening causes of blackouts

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

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    • Arrhythmias (irregular heartbeats)

    • Cardiomyopathy (weakened or abnormal heart muscle and function)

    • Epilepsy

    • Heart valve diseases and disorders

    • Myocardial infarction (heart attack)

    • Seizures

    • Severe infection

    • Stroke

    • Traumatic injury

    Questions for diagnosing the cause of blackouts

    To diagnose your condition, your doctor or licensed health care practitioner will ask you several questions related to your blackouts including:


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    • Can you remember things that happened recently?

    • Do you remember what you did after your blackout?

    • Do you remember what you were doing before your blackout?

    • Have you ever had a seizure?

    • Have you had any recent injuries or surgeries?

    • What medications are you taking?

    • What other symptoms occurred with your blackout?

    • When did your blackout occur?

    • When was your last drink of alcohol?

    What are the potential complications of blackouts?

    The potential complications of blackouts depend on the underlying cause. Because blackouts 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:

    • Brain damage
    • Injury during a blackout episode
    • Neurological problems, such as memory loss and confusion
    • Permanent nerve damage, including paralysis
    Medical Reviewers: William C. Lloyd III, MD, FACS Last Review Date: Oct 16, 2016

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    Medical References

    1. Memory loss. Medline Plus, a service of the National Library of Medicine National Institutes of Health.
    2. Amnesia. University of Iowa Hospitals and Clinics Health Topics.

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