Here's a tip: If you're an organ donor, try not to die on a weekend.

According to new findings presented at the American Society of Nephrology's Kidney Week, perfectly good donor kidneys are being thrown into the garbage at an alarming rate when those kidneys are procured over the weekend. 

Because hospitals have fewer resources and staff on Fridays and Saturdays, emphasis must be placed on the most critical procedures, including life-or-death scenarios, so when a patient passes away unexpectedly, his or her kidneys may not be harvested in time to make them suitable for transplantation. Further, those kidneys that are harvested from weekend cadavers are 20 percent more likely to be discarded despite being of suitable quality for donation.

"Recognition of the impact of factors beyond organ quality on the procurement and transplantation of deceased donor organs should influence future policy aimed at improving kidney transplantation rates in the United States," said study leader Dr. Sumit Mohan, M.D., in a press release.

As you might expect, larger hospitals and medical centers with more staff and infrastructure are better able to handle unforeseen deaths and urgent organ harvesting, so donors who pass away at a larger center are more likely to have their wishes to donate carried out.

While any number of discarded usable organs is disturbing, it is important to understand these numbers in perspective. In 2014, there were 24,000 organ transplants from deceased donors and 6,000 from living donors. According to the new findings, 89.5 percent of healthy donor kidneys are harvested over the weekend, while 90.2 percent are harvested during the week. The difference is small but significant. The best time to donate an organ, based on this new data, is Monday. The study will be published once it has been discussed at Kidney Week, Nov. 3 to 8.

The loss of potentially life-saving organs is an especially critical issue given that in the U.S., 21 people die every day while waiting for an organ. Although most Americans (90 percent) say they agree in principle with organ donation, only 40 percent have registered as organ donors, a relatively simple process. According to the University of Southern California's Olivia LaVoice, donors must be completely and irreversibly brain-dead before a doctor can consider harvesting their organs.

The United Network for Organ Sharing says that 122,661 people are waiting for a lifesaving organ transplant. To these people and their families, one lost organ is one too many.