If you're planning a big weekend with the chance of a hangover come Monday, you might want to think twice about when you return to work.
According to new research, you're actually better to pull a sickie, which shows just how much hangovers cost in lost productivity.
University of Otago research has found hangovers cost workplaces more than $1.65 billion a year.
"From an employer's point of view you might be able to spot someone that continuously takes Mondays off, but you're not going to see if they're at work and perhaps not working to their best," Dr Trudy Sullivan, one of the study's researchers, told Newshub.
The cost of lost productivity from an employee taking a sick day is just over 200 dollars a year.
However, surprisingly, it's four times as much if that employee turns up to work, because of the loss in work quality and risk of injury.
"We asked employees if they had to cover for their co-workers as a result of their co-workers' drinking and 20 percent said that they had, so I guess that's a bit higher than we thought and that estimate of $1.65 billion doesn't include those costs," Dr Sullivan added.
Monday hangovers may be more common with the rise of so-called Sunday sessions and all-day bottomless brunches offered in bars.
"Sunday used to be a dead place, people never used to go out on Sundays, but I think the trend is changing - people are going out, people are more about going out, trying new things," Lalit Arora from Auckland bar Portland Public House told Newshub.
And if you wake up with a hangover like the movie, calling in sick is the least of your worries.