Marijuana and blood donation what you need to remember? We all know smoking and vaping isn't great for your health. But it doesn't stop you from being a blood or plasma donor. Just make sure to wait one hour after donating Myth: You can't donate blood if you smoke or drink. Fact: Smoking or occasional drinking doesn't automatically disqualify you. But avoid alcohol for at least 24 hours before donating to Can You Donate Plasma if You Smoke Marijuana?