If done correctly and under the right conditions (the time of day, the length of the nap, and so on), having a quick nap can be extremely good for your health. In other words, how and when you nap determines if it good or bad for you. So to simplify things, here are some easy to understand do’s and don’ts for taking a restorative nap without spoiling your nightly sleep schedule according to the sleep experts.

A solid nap can improve your mood and energy level and help you feel refreshed and improve both our physical and cognitive performance. Those brief moments of sleep can improve strength, power, and stamina, as well as a person’s ability to learn and retain information. Napping can also boost your heart health, according to a British study where nearly 3,500 people found that those who napped once or twice a week were 48% less likely to experience a cardiovascular event, like a heart attack, than those who didn’t nap.

Having said that the research is conflicting, because one 2015 meta-analysis of 11 studies discovered that people who nap for one hour or more a day had a 1.82 times higher rate of cardiovascular disease than those who didn’t nap. But according to Carolyn D’Ambrosio, M.D., FCCP, associate professor of pulmonary medicine at Yale University School of Medicine and chair of the Sleep Medicine Network with the American College of Chest Physicians, it isn’t always the nap itself that’s the source of harm, but the reason behind the nap.

This is because napping routinely can be a sign of poor sleep quality or significant sleep deprivation, both of which can be bad for you as they increase risk of cardiovascular disease, diabetes and depression.

To get the full benefits of napping without oversleeping, it’s wise to follow some proper napping best practices.

How Long Is A Smart Nap?

It’s best to limit your naps to 20 minutes according to The National Sleep Foundation. A 20-minute nap provides you with some light sleep without dipping into the deeper stages of sleep—this helps you feel refreshed and still avoid throwing off your nighttime sleep. Naps that last longer than 30 minutes, on the other hand, can make you feel groggy or impaired.

Having said that however, a longer nap that lasts around an hour and a half has benefits too, especially if you work shifts. Though longer naps can make you feel more tired or drowsy, a 90-minute nap allows your body to sleep through a whole sleep cycle—or cycle each phase of sleep one time, a process that typically takes 90 to 110 minutes—without interruption.

2020 study from the International Journal of Environmental Research and Public Health found that 90-minute naps were more beneficial than 40-minute naps when it came to improving attention, physical performance, mood, muscle recovery, and feelings of fatigue in male athletes.

The best time to take a nap is in the early afternoon, because napping too close to bedtime, anytime at or after 3pm can result in fragmented sleep or poor sleep quality.

So long story short, napping is fine, so long as it’s done right. A quick 20 minute kip to boost alertness and decrease drowsiness, is good, but if you find yourself napping often throughout the day despite getting the recommended seven-plus hours of sleep at night, there may be an underlying reason for your frequent tiredness that you would be smart to get checked out.