Platelets form blood clots and stop bleeding. Someone in the United States needs a platelet transfusion every 30 seconds, the Red Cross reports.

Cancer patients, for instance. Undergoing cancer treatment causes low platelet counts, according to the Red Cross, and that puts a patient at risk of serious bleeding.

Or trauma victims and surgery patients. When they bleed, they lose platelets — which are vital to their survival.

Transplant patients need platelets too. So do people with blood disorders.

But platelets can’t be stored indefinitely. They must be used within five days of collection.

Thus the constant need for platelets.