Recent Blog Articles

Blacking Out, Fainting, or Loss of Consciousness

November 24, 2020

Welcome.

The two main reasons for blacking out are insufficient blood flow to the brain and abnormal electrical activity within the brain (a seizure).

While both of these sound scary, in reality most episodes of blacking out are not related to life threatening health problems.

This guide is designed to provide insight into why you passed out. It is not a diagnostic tool or a substitute for evaluation by a health professional.

The questions are ones your doctor is likely to ask you. Your answers provide a path to better understanding of the common reasons for losing consciousness.

Let's begin.

Certain situations demand emergency medical care.

Do any of the following apply to you?

- Chest pain or shortness of breath before or after you passed out

- Bloody or black stools

- Severe headache

- Recent blow to the head

- A heart condition

Yes, one of those applies to me.

No, none of those apply to me.

To continue reading this article, you must log in.

Subscribe to Harvard Health Online for immediate access to health news and information from Harvard Medical School.

  • Research health conditions
  • Check your symptoms
  • Prepare for a doctor's visit or test
  • Find the best treatments and procedures for you
  • Explore options for better nutrition and exercise
Learn more about the many benefits and features of joining Harvard Health Online »

I'd like to receive access to Harvard Health Online for only $4.99 a month.

Sign Me Up

Already a member? Login ».

Disclaimer:

As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review or update on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

Free Healthbeat Signup

Get the latest in health news delivered to your inbox!

Harvard Health Publishing Logo

Thanks for visiting. Don't miss your FREE gift.

The Best Diets for Cognitive Fitness, is yours absolutely FREE when you sign up to receive Health Alerts from Harvard Medical School

Sign up to get tips for living a healthy lifestyle, with ways to fight inflammation and improve cognitive health, plus the latest advances in preventative medicine, diet and exercise, pain relief, blood pressure and cholesterol management, and more.

Harvard Health Publishing Logo

Health Alerts from Harvard Medical School

Get helpful tips and guidance for everything from fighting inflammation to finding the best diets for weight loss...from exercises to build a stronger core to advice on treating cataracts. PLUS, the latest news on medical advances and breakthroughs from Harvard Medical School experts.

BONUS! Sign up now and
get a FREE copy of the
Best Diets for Cognitive Fitness

Harvard Health Publishing Logo

Stay on top of latest health news from Harvard Medical School.

Plus, get a FREE copy of the Best Diets for Cognitive Fitness.