Even if you consume cannabis, you can still donate blood
Here's a quick PSA as we head through National Blood Donation month (and maybe you've already seen the Red Cross at your work, asking for blood donations). If you smoke, eat, or vape cannabis, you can still give blood. Well, not while you're high, but you don't need to worry about leftover THC or CBD in your system at all. So says the American Red Cross: "While the Red Cross does not encourage the use of controlled substances, marijuana or alcohol use does not necessarily disqualify you from giving blood as long as you are feeling well. If you have EVER injected any illegal drugs, you can never give blood."
They also say that if you are actually under the influence, you shouldn't be showing up to give blood (which makes sense). As long as you're sober at the time, however, you shouldn't have any concerns -- go give blood!
You can look over here to find a local drive to give blood this month. The technology and the systems around the annual blood drives are incredible, and of course every drop of blood donated could help to save someone's life somewhere in the world. If you have the chance to give blood this month or any other, definitely take it.