I workout in the AM, so I just donated later in the afternoon.
I donated blood and set a new front squat PR the next day, it’s all in your head.
I give blood often. I usually just workout before I donate. In my case, since I tend to lift later in the day, I get extra recovery time (24 hrs + the next morning).
In either case, drink lots of fluids before and after.
I’m pushing over a gallon now and have never had any complications from it. Hydration is the biggest thing that will prevent you from bruising and feeling nauseous, it barely affects me anymore.
I’ve lifted anywhere’s from an hour to 8 hours after and never had a problem, but never with cardio intensive workouts. But like WestCoast said, if you do anything too strenuous too soon there’s a risk inherent with it. If you can I’d say take a much needed day off and come back for the next day.