exhaustion after donating blood

I'm a regular blood donor and donated Friday, the first time after starting tirz, and I have been wiped out. I've had no negative side effects from tirz, but since Friday I've been lightheaded and tired, and going to the gym I had to sit down a few times because I was afraid of blacking out. I've increased my protein and water, but continue to feel the same. Anyone else have this extreme reaction to donating blood? As a boring person I feel like giving my blood is one of the benefits :)