It is important to make an appointment when donating blood. Donors who set up an appointment ahead of time will be served first by the crew of the Blood Center of Wisconsin. They can have you in-and-out in 20 minutes to a half hour. Walk-in donors are also appreciated, but if you are on a tight time schedule it may not be as convenient for you. It takes less time if you are a regular donor because there is less paperwork that is required.