Can You Donate Blood If You Use Cannabis? Alternaleaf UK Smoking (or vaping) doesn't affect your ability to donate blood. Help us bust this myth by sharing our post. If you use cannabis, do it safely Harvard Health Marijuana and blood donation what you need to remember? Think you can't donate blood? Think again. Australian Red Cross Lifeblood 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