The American Red Cross calls on eligible donors with all blood types to help maintain a sufficient blood supply this summer. The American Red Cross encourages all eligible blood donors to make an appointment to donate blood soon to help prevent a shortage. During the summer months, on average, about two fewer donors give blood at each Red Cross blood drive than what is needed to meet the needs of patients. Vacations and summer activities are among the reasons regular donors may not find the time to give. But, patients don’t get a vacation from needing blood – the need is constant.