If you’ve gotta pee like a racehorse, you’ve got some serious peeing to do: Racehorses urinate up to 2 gallons a day. Yes, as you sit down to watch the Kentucky Derby tomorrow, know that the idiom is accurate, Slate explains. An average man urinates 1 to 2 quarts daily. The expression may date back to the 1970s, writes David Sessions. That’s when diuretics, including Lasix, became more popular.
Lasix “inhibits the absorption of sodium and draws water into the bladder,” prompting more urination, to the point of gallons of pee in an hour. That can make a horse 10 pounds lighter—and thus faster—before the race begins. However, the drug is meant only to be used against internal bleeding; trainers aren’t “supposed to use it strictly as a diuretic.”