Warfarin’s story starts with a surprise twist—it was originally a rat poison! In the 1920s, scientists discovered that spoiled hay made of sweet clover (which cattle had eaten) caused animals to bleed to death. They found that a chemical in the clover interfered with blood clotting, and they used it to create a rat poison.

Fast forward to the 1940s, when doctors realized this same substance could prevent blood clots in humans. It worked by blocking vitamin K, which is needed for blood clotting. So, the rat poison became a potential blood thinner.

After some careful testing, scientists figured out how to use warfarin safely in humans. By the 1950s, it was approved as a medicine to treat and prevent dangerous blood clots, saving lives in the process.

From rat poison to life-saving drug—warfarin’s journey is proof that science is full of unexpected discoveries!