Dehydration
Plasma contains a lot of water. For that reason, some people experience dehydration after donating plasma. Dehydration after donating plasma is usually not severe.
Dizziness, fainting, and lightheadedness
Plasma is rich in nutrients and salts. These are important in keeping the body alert and functioning properly. Losing some of these substances through plasma donation can lead to an electrolyte imbalance. This can result in dizziness, fainting, and lightheadedness.