Can I be turned away from donating blood if I keep having those symptoms...?!

Your reactions are fairly common. They are caused by a drop in blood pressure after blood donation.

Phlebotomists are not mind readers. It is your responsibility to inform the staff (preferably prior to donation) that you have had these reactions in the past. This way steps can be taken to prevent the reaction and or lower the chance of you injuring yourself if you do have a reaction.

The conversation should go something like this:
Phlebotomist: "Hi, which arm do you usually donate with?"
You: "Oh, either. Listen, I tend to get very dizzy about 10 minutes after I donate, I just thought I should let you know."
Phlebotomist: "I'm glad you said something. Have you eaten yet today?"
You: "I had lunch about two hours ago"
Phlebotomist: "Good, how about I get you a juice to drink before we start the donation? I little extra fluid in your system can help you feel better afterward. Also, I am going to keep your head in a slightly lower position than you are used to for this donation. After you have given the pint, i'd like to have you drink some more juice before you get out of the chair. Then you can dangle your feet off the side for a few minutes before standing up all the way. Once you do get out to the refreshment area, please sit there for a good 15 minutes before you leave the blood drive"

See, easy-peasy!

I suggest you always make sure you have had a meal within 2 hours of your donation, and drink 8-16 ounces of water or juice withing a half hour of the donation. Getting up slowly and dangling your feet will give you an idea if you are going to get dizzy. If you do, all you have to do is swing your feet back up. This leaves you with less chance of falling down on hard flooring. I also recommend eating something salty after your donation, if your blood center does not provide salty snacks, bring a small bag of chips or pretzels with you to nosh on afterward.

Prevention is the best medicine for these symptoms. You will not be turned away be cause you get dizzy after losing a pint of blood. However, if you allow it to escalate, you could get hurt if you feel faint while on a stairway or a busy street.

14+ years as a phlebotomist for a major blood center

if you tell them of these symptoms, yes, they will note it.and, yes, you can be turned away from donation. unfortunately, some donation centers don't get concerned about such symptoms although they should. i had the same experience only i did faint, only to be unnoticed and was believed to be sleeping. i woke up in a cold sweat with barely any blood pressure. were i you, i would consult a physician for advice but until you do that, i would NOT, i repeat, NOT give blood. why chance a possible unnoticed life-threatening experience if you don't have to. by consulting a physician, you may find that it is nothing or maybe something else is causing these symptoms. good luck!