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What Is a Greyout?

By Elizabeth West
Updated Mar 03, 2024
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A greyout occurs when a person is on the verge of fainting, or syncope. Vision fades and light and color are reduced to a grey, washed-out blur. There will often be a loss of peripheral vision in a sort of tunnel effect which is caused by a drop in blood pressure to the brain, such as when suddenly standing from a reclined position or possibly a serious medical condition. The effect of this event, also called presyncope, is temporary, and lying down will usually cure it.

Syncope has numerous causes, but the primary cause is decreased blood flow to the brain. The problem has generally a short duration because when a person who has fainted falls or reclines, the blood no longer needs to push against gravity to reach the brain and is restored. Pale skin, hyperventilation, and nausea may accompany the greyout, followed by a profound weakness of the limbs. The legs fold and the person collapses unless they are able to get to a chair or lie flat.

Fighter pilots may experience a greyout if they are subject to high-speed maneuvers that exert positive g-forces on their bodies. The pressure forces the blood to the lower extremities and away from the brain, causing presyncope symptoms. Wearing a G-suit to control the flow of blood to the lower body can prevent it. People who ride big roller coasters have suffered the same effects on the tight turns and sharp loops the rides sometimes take.

While fainting is not usually serious, certain cardiac conditions can predispose people to sudden blackouts. Cardiac syncope can be a sign that a life-threatening event is occurring, so all episodes of unexpected syncope should be taken seriously. Other people suffer from situational syncope, where fainting is triggered only in certain circumstances. Coughing and defecating can cause a drop in cranial blood pressure, and in elderly people postprandial syncope can sometimes happen after eating. Situational syncopes often are accompanied by presyncope symptoms such as greyout, dizziness, and tunnel vision.

First aid for presyncope symptoms recommends that the person sit down and put the head between the legs or lie on the floor with legs elevated. Blood will then be directed back toward the brain, relieving the symptoms and possibly preventing loss of consciousness. A visit to the doctor is necessary if a person has repeated fainting episodes or greyouts to rule out any serious medical conditions.

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Discussion Comments

By anon994121 — On Jan 15, 2016

Any grey out (whiteout) instances involving a detached retina?

By anon946256 — On Apr 18, 2014

This happened to me while driving the other day. Everything went white and I couldn't find a side road because of it and I knew if I kept going I would faint. It was the scariest thing. I was on the way to the pharmacy after leaving my doctor for relief of a 24 hour migraine.

By ysmina — On Aug 31, 2013

I had this happen to me once during an anxiety attack. I was hyperventilating, so that's probably why. It definitely is scary though. I hope I never have it again.

By stoneMason — On Aug 30, 2013

@simrin-- There could be many possible reasons. Some basic blood tests are a good place to start.

My sister has a greyout about once a week when she doesn't take her iron supplements. She has a severe iron deficiency.

She never loses consciousness but she falls down and can't see or hear well for a while. Lying down helps and I usually put a cold compress on her forehead while she recovers. She doesn't get them if she takes her supplements like she's supposed to.

By SteamLouis — On Aug 30, 2013

This has happened to me twice in the past week. I'm very scared. I have an appointment with my doctor tomorrow and will get a few diagnostic tests. Why would someone start having greyouts suddenly?

By Ana1234 — On Aug 30, 2013

@croydon - I've noticed that this tends to happen to me if I've let myself get too dehydrated or if my iron levels are low. Often I won't even notice until I'll try to stand up too suddenly and then the room will spin, my head will feel all liquidy and hot and I'll usually have to sit right back down again.

If I have a lot of water to drink and make sure I take an iron supplement these symptoms go away. It makes sense, because those things are related to blood pressure and ability to carry oxygen.

It's possible that you might have had this as a problem when you were a kid and no one picked it up. The child of one of my friends has problems with keeping herself hydrated and she gets dizzy a lot when she forgets to keep her fluids up.

By croydon — On Aug 29, 2013

@Iluviaporos - I used to greyout all the time when I was a kid, to the point where my mother thought I might have some kind of epilepsy. She got me taken for all kinds of tests and in the end the doctors decided it was a kind of migraine.

Honestly, I think I just liked to spin around too much and would get dizzy. I always felt guilty that my mother spend time and money on my supposed illness and it didn't turn out to be anything.

By lluviaporos — On Aug 28, 2013

I experienced this quite badly only once, when I was a kid and I managed to slip on a patch of ice on a street in town. I was walking with my father and grandfather and I landed flat on my back, and was unable to breathe for a few moments. I honestly thought I was going to die and I remember my vision went all blurry. I guess I greyed out because my brain wasn't getting enough oxygen for a while.

I wanted to cry, but my father kind of hauled me up and shushed me, because my grandfather was sick and he didn't want to upset him.

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