Why might individuals feel light-headed after donating plasma?

Feeling light-headed after donating plasma often occurs because of the loss of fluid volume and a subsequent drop in blood pressure. When a person donates plasma, about a liter of this component is typically collected, which can lead to a temporary decrease in the overall fluid volume in the body. The body's blood pressure is closely linked to the volume of circulating blood; therefore, when plasma is removed, this can create a drop in blood pressure.

As fluid levels decrease, the heart may struggle to pump adequately, leading to insufficient blood flow to the brain, and this can manifest as light-headedness or dizziness. It's important for donors to be properly hydrated before and after donating to mitigate these effects and maintain their blood volume and blood pressure.