We’d all love to have a few extra hours in the day.

But stealing from bedtime isn’t the way to go — if you care about your performance at work, that is. Because even though you might think you can do your job with a major sleep deficit, science suggests otherwise.

A study in the journal Sleep found that subjects who got just six hours of sleep per night for two weeks functioned as badly as if they were deprived of sleep for 48 hours. The study's subjects actually thought they were performing well.

“Many people take pride in the fact that they don’t get enough sleep,” says W. David Brown, Ph.D., a sleep psychologist and author of “Sleeping Your Way to the Top: How to Get the Sleep You Need to Succeed.” Six hours a night actually leaves your brain as addled as if you’d been drinking, reports another study.

Knowing all the ways extreme fatigue impacts your performance might convince you to change your ways. These seven consequences spell it all out.

Your Judgment Takes a Hit

Maybe you’ve interviewed several job candidates, but you keep going through their résumés because you can't put a face to their accomplishments. Or your department holds an emergency meeting to decide about cutting loose a difficult client, and it's taking you a while to size up the situation.

No wonder: An ongoing sleep deficit short-circuits the part of the brain that handles decision-making and problem-solving, says Richard Shane, Ph.D., a behavioral sleep specialist. That leads to your needing lots of time to make a judgment call.

And if you’re faced with a moral dilemma — for example, whether to give credit to a coworker who assisted you on a report — sleep deprivation puts you at a disadvantage. Not sleeping enough also affects your ability to make appropriate ethical judgments, finds another study published in Sleep.

You’re Moody and Irritable

Ever find yourself snapping at junior staffers or letting small things get to you? When your sleep needs haven’t been met, exhaustion triggers mood swings.

“Emotions reside in a part of the brain called the amygdala,” Brown says. The amygdala usually communicates with the cortex (which influences awareness and perception) to process emotions. But when you’re sleep-deprived, the amygdala ignores the cortex and moves straight into fight-or-flight mode, throwing logic out the window, Brown explains.

“[That results in] anger and a stronger form of irritability; you’re more stressed and you’re more depressed,” Shane says. You’re also prone to overreacting. Too little sleep could also intensify depression, finds a 2014 study.

You Show Up at Work but Aren’t Really There

If you log the occasional late night, the next day you feel OK but you’re just going through the motions. When you regularly skip sleep, that’s what you’re like every day.

“We’re now using a term called presenteeism, which is when employees show up to work but get very little done because they are so sleep-deprived they aren’t functioning optimally,” Brown says. These employees are physically present without really being mentally present because their brains are fatigued.

You’re Accident-Prone

“About 70% of accidents are human-related — they don’t happen randomly,” Brown says. A major contributing factor? Exhaustion. “Accidents tend to occur between midnight and 6 a.m. and 2 and 4 in the afternoon,” Brown says. “Those times correspond exactly with the tendency for humans to fall asleep.”

Insomnia contributes to 7.2% of costly workplace accidents, amounting to $31 billion each year, reports one study. Even if you work at a desk, you’re more likely to trip and fall, scald yourself with hot coffee or get into an accident on your commute.

You Use Up a Lot of Sick Days

Sleep deprivation also affects your immune system. “When you sleep poorly, you have three times the amount of sickness,” Shane says.

Not to mention major health issues like diabetes, obesity, heart disease and high blood pressure are linked to sleep quantity, Shane says. “You have one night of poor sleep, and you notice the effects,” he says. “That’s proof right there that sleep is vitally important to your health, like exercise and nutrition.”

You Can’t Remember a Client’s Name

Not getting enough sleep warps your memory. “Sleep does seem important for consolidating not just facts and figures in our memory but mechanical movements,” Brown says.

Getting plenty of sleep both before learning and after learning makes a difference in what and how much you recall.

You Make a Poor Impression on Your Team

Think you’ve trained yourself to function fine on six hours' sleep? Fatigue is pulling the wool over your eyes.

When sleep-deprived professionals behave similarly to people who are intoxicated, they, too will deny that anything’s off. “When people are drunk, a lot of times they don’t know that they’re drunk, and they’ll tell you they’re not drunk,” Shane says. “It’s the exact same thing when people are sleep-deprived. They think everything’s OK and they can function just as well,” but their colleagues know better.