If you have a busy schedule (and who doesn’t?), chances are you’ve set your alarm for an ungodly hour of the morning in order to squeeze in a workout. Most of the time it just takes a little discipline to drag yourself out of the comfort of your bed, but when your alarm is blaring after a night of tossing and turning and you just can’t shake your sleepiness, should you suck it up or snooze?

Sufficient sleep and exercise are both integral to your health, but if you’re faced with having to sacrifice much-needed  shuteye or a good sweat,  sleep is the answer, says Sina A. Gharib, M.D., sleep researcher and associate professor of medicine at the University of Washington.

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Sleep helps to regulate your hormones and immune system, says Nathaniel F. Watson, M.D., board certified neurologist and sleep specialist at University of Washington Sleep Center. So routinely getting fewer than seven hours of sleep a night can lead to serious side effects that can sabotage your health, such as metabolic disorders, cardiovascular disease, decreased immunity, and obesity.

Plus, if you’re chronically sleep deprived, your early-morning session could be doing more harm than good: You might just sabotage the size or strength gains, or fat-loss results you’re looking to see from your workouts. “Without adequate sleep, our bodies don’t get a chance to recover and rebuild after a workout, meaning they’re in constant breakdown mode,” says says Jim O’Brien, C.P.T., and certified group fitness instructor for Orangetheory Fitness. Not to mention, your workouts themselves will probably decline if you’re feeling super tired, he says. No one wants to walk out of the gym feeling even more zonked than when they walked in.

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So how can you tell when to push through and when to hit snooze? Be on the lookout for signs of chronic fatigue: “Sleep deprivation causes excessive daytime sleepiness, difficulty focusing, and even feelings of depression,” warns Gharib. If you can’t stay awake and alert throughout the day without caffeine, or if you sleep much longer on weekends than you do on weekdays, you aren’t getting enough regular sleep, cautions Watson.

To avoid having to sacrifice your workouts to catch more Zzz’s, O’Brien recommends setting a bedtime for yourself and sticking to it. Then, to avoid falling into a black hole of Facebook videos, put your phone on silent mode and out of reach. If you use your phone for your alarm, then you’ll have to get out of bed to turn it off in the morning.

If A.M. training sessions continue to feel like too much of a struggle, you may want to consider hitting the gym after work or dinner—just keep in mind that exercise stimulates the body, and a nighttime workout may cause some people to have trouble falling asleep afterward, according to Watson. He recommends you leave at least one to two hours between the end of your workout and the time you want to hit the sack. Once you’ve got your sleep schedule on lock, though, it’ll be easier to identify what time of day works best for your workouts.

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