Giving blood to people who desperately need it is an essential part of modern medicine.

The first documented vascular transfusion came in 1667, when a doctor in the court of King Louis XIV transfused the blood of a sheep into a 15-year-old boy. Believe it or not, the boy survived.

The first human-to-human transfusion happened in 1818, when 12 to 14 ounces of a donor's blood was injected into a person with massive internal injuries. That patient initially rallied, but eventually succumbed to the injuries.

Since then, the process has become very safe and streamlined.

Today in the U.S., nearly 21 million portions of blood components — either whole blood, red blood cells, plasma, cryoprecipitate, or platelets — are transfused every year.

Unfortunately, there are times when life-saving blood is in short supply. Like right now.

There have been two consecutive months of below-normal donation rates; the Red Cross says that it now has a 61,000-unit deficit.

So if you have never donated blood, now's the time. It’s safe, fast and without negative repercussions.

• You will be interviewed to discover if there is any reason you are not a candidate; so let the folks screen you.

• You cannot contract a disease giving blood to the Red Cross; all needles and procedures are sterile.

• You can spare the blood; your body quickly replenishes what's taken. You're allowed to donate five times a year.