Why did you pass out during the blood draw?

10 years ago | Doctors

By pH health care professionals

Fainting – It can happen to otherwise healthy people! You may feel faint and lightheaded and then suddenly lose consciousness or pass out.

The most common cause of fainting (especially among children and young adults) is neurally mediated syncope, which is also commonly referred to as vasovagal syncope or a vasovagal response. In a vasovagal response, your blood pressure drops and the heart does not pump a normal amount of oxygen to the brain. The response is often triggered by anxiety or emotional distress, sometimes even from the sight of blood during a blood draw. This type of fainting can lead to minor injuries, like cuts or bruises from falling, but it is considered to be relatively harmless in most cases.

Before a vasovagal response, your skin may become pale, you may feel lightheaded, start to lose some vision (tunnel vision) and/or experience blurred vision. You may feel nausea, warmth or a cold sweat. You may even start yawning. Other people in the room may notice your pupils becoming dilated or notice you making jerky movements. You also might have a slow and weak pulse.

So what steps can you take to prevent fainting during your blood draw?

Tensing your muscles or crossing your legs at the onset of symptoms may help postpone or prevent fainting. You also may lie down and elevate your legs. If you have fainted at a blood draw before, you should ask to do your next blood draw lying down.

You can also reduce your likelihood of fainting by doing the following:

Try not to skip meals.
Don’t fast for too long.
Stay hydrated.
Avoid standing for prolonged periods of time.
Reduce caffeine and alcohol intake.
Try sleeping with your legs elevated.
Consider wearing elastic stockings to keep blood from pooling in your legs (which would reduce blood flow to your brain!).
Be proactive and talk to the nurse or phlebotomist before your blood draw and let him/her know if you have fainted before.

Enjoy Your Healthy Life!

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Comments (2)

Guest

I swear its hit or miss whenever I get my blood drawn. Partly I think too it depends on how much they are taking. If I know a person is getting 5 vials of blood it freaks me out more (since you can hear the nurse opening and closing each of the vials as they insert them to get blood). Sometimes its the prick of the needle. I never ever look at it!

Guest

@guest That's so true! I've had my blood drawn before and never had any problems, but usually it was only one vial that they took. I'm pregnant with my first child and just got my blood drawn today. The phlebotomist took 5 VIALS! After I heard her cap off the second one I lost it. My vision went out, then my hearing, and then I was out for like a minute. It was so weird it's never happened to me before and I wasn't even nervous about it until I heard that second vial pop haha.