MARSHFIELD, Wis. — The BloodCenter of Wisconsin is bracing for a blood shortage this summer, when donations traditionally drop by about 20 percent. That's mainly because blood drives at high schools and universities shut down with students on break.

Vicki Bohman helps run the BloodCenter's donor center in Marshfield. She told News-Herald Media (http://mnhne.ws/15n05gA) for a Thursday report that the shortage could cause problems for hospitals that rely on the center's donations.

"A lot of our blood supply comes from high schools and universities, and they're not in session, which impacts our ability to collect blood," Bohman said. "Another reason is a lot of people ... get out of their habits of donating because they're on vacation or out and about enjoying the nice summer weather."

Bohman said the BloodCenter must collect about 800 units of blood each day to meet the demand at 59 hospitals statewide. Type O-negative blood is needed most because it fits patients of any blood type and is often used in emergency situations.

A shortage could be especially challenging for places like Ministry Saint Joseph's Hospital, which receives all its donated blood from BloodCenter of Wisconsin sites.

To encourage donations the BloodCenter is giving out free tickets to the Central Wisconsin State Fair at upcoming Marshfield blood drives.

About 25 donors already had donated blood during the first hour of a community blood drive Wednesday at Marshfield's American Legion Hall. Some were regular donors.

"I usually give blood on a regular basis," said Heather Binder of Arpin, a donor for more than 10 years.

Ashley Held, of Stevens Point, said she gives blood every eight weeks.

"I started giving blood because my dad has done it his whole life religiously every eight weeks," She added.