What is the negative side of donating plasma?

The same as blood donation, but any side effects are temporary in nature.

These include light headedness, malaise and general washed out feelings.

After all you have just donated a PINT of your blood.

Same as donating your whole blood, none. Perhaps a bit weak or dizzy for 30 minutes. Sleep well, drink fluids, and eat a non fatty meal before donating, and don't donate if you are getting a cold or the flu. You will be screened and all this will be explained in detail.

(Some people go from bank to bank to sell, lying about how often they are going - not a good idea, even though a healthy person might get away with it in terms of how their body can replenish. But you said donate.)

It is a wonderful and life giving process.

Very little. It takes a bit longer than donating whole blood, you usually have to make an appointment rather than walking in off the street, and you need to go to a special clinic.

It has some advantages, in that you don't lose your red cells, so if you are prone to low iron levels, giving plasma means less recovery time.

I worked out that a pint of blood takes 700 calories to replace. I suspect plasma is less.

You can give plasma more often than whole blood so if you are working towards prizes, you'll get there quickly. I'm up to 116 units of blood, and a fair few of those are plasma.