Most adults need 7 to 9 hours of sleep per night. The specific number depends on your age, with younger people needing significantly more and the range narrowing slightly after age 65. But hitting the right number of hours is only part of the equation. How well you sleep, how consistent your schedule is, and how you feel during the day all factor into whether you’re actually getting enough.
Recommended Hours by Age
The CDC breaks sleep recommendations into nine age groups, reflecting how dramatically sleep needs change across a lifetime. Newborns (0 to 3 months) need 14 to 17 hours per day. Infants from 4 to 12 months need 12 to 16 hours including naps, and toddlers (1 to 2 years) need 11 to 14 hours including naps. Preschoolers aged 3 to 5 still need 10 to 13 hours with naps, and school-age children (6 to 12) need 9 to 12 hours.
Teenagers between 13 and 17 need 8 to 10 hours, which is worth noting because most high schoolers fall well short of that. For adults aged 18 to 60, the recommendation is 7 or more hours per night. Adults 61 to 64 should aim for 7 to 9 hours, and those 65 and older do well with 7 to 8 hours. The National Sleep Foundation confirms that 7 to 9 hours remains the consensus target for most adults, paired with consistent sleep and wake times.
What Happens When You Sleep Less Than 7 Hours
Consistently sleeping under 7 hours changes your body in measurable ways, starting with the hormones that control hunger. Short sleep increases ghrelin, the hormone that drives appetite, and decreases leptin, the hormone that signals fullness. The result is a persistent feeling of hunger that isn’t actually tied to your body’s energy needs. Sleep deprivation also activates the same biological system that cannabis targets (the endocannabinoid system), which may explain why people who are underslept tend to crave high-calorie foods, especially late at night. Over time, this pattern is linked to a 38 percent increase in the likelihood of obesity.
Your stress hormones get disrupted too. Cortisol normally peaks around 9 a.m. and drops to its lowest point near midnight. When you regularly delay your bedtime or sleep too little, that rhythm shifts, pushing cortisol levels higher during the middle of the day. Sustained high cortisol promotes belly fat accumulation, increases insulin levels, and raises the risk of prediabetes and type 2 diabetes. It also creates a frustrating cycle: elevated daytime cortisol makes you feel more stressed, triggers more food cravings, and makes it harder to fall asleep the next night.
Heart Disease and Chronic Sleep Loss
The cardiovascular risks of short sleep are well documented. Habitually sleeping less than six hours a night is linked to a 20 percent higher incidence of heart attacks, based on data from more than half a million people published in the Journal of the American College of Cardiology. When short sleep combines with other sleep problems (like trouble falling or staying asleep), the risk climbs further. One study found that middle-aged people dealing with multiple sleep issues, including fewer than six hours per night, had nearly three times the risk of heart disease.
These numbers help explain why sleep researchers treat the 7-hour minimum as a genuine health threshold, not just a suggestion. The drop from 7 hours to 6 isn’t trivial. It places you in a risk category comparable to other well-known cardiovascular risk factors.
Quality Matters, Not Just Hours
Spending 8 hours in bed doesn’t guarantee 8 hours of restorative sleep. Your body cycles through distinct sleep stages throughout the night, and two of them carry the heaviest load for physical and mental recovery. Deep sleep (stage 3) makes up about 25 percent of total sleep time in adults and is when the body repairs tissue, strengthens the immune system, and consolidates memory. REM sleep, the stage associated with dreaming and emotional processing, accounts for another 25 percent.
If you’re waking frequently, drinking alcohol before bed, or sleeping in an environment that’s too warm or too noisy, you may be shortchanging these stages even when your total hours look adequate on paper. The clearest signal that your sleep quality is sufficient: you wake up feeling rested and can stay alert through the day without needing caffeine to function.
How to Tell If You’re Getting Enough
One practical way to evaluate your sleep is to pay attention to how drowsy you feel during routine, low-stimulation activities. Clinicians use a tool called the Epworth Sleepiness Scale, which asks you to rate your likelihood of dozing off during eight common situations: reading, watching TV, sitting in a meeting, riding as a car passenger for an hour, lying down in the afternoon, sitting and talking to someone, sitting quietly after lunch, and sitting in stopped traffic. You rate each scenario from 0 (no chance of dozing) to 3 (high chance), giving you a total score between 0 and 24.
A score of 0 to 10 falls within normal daytime sleepiness. Anything from 11 to 12 suggests mild excessive sleepiness, 13 to 15 is moderate, and 16 to 24 is severe. You can run through these questions honestly in about two minutes, and the result gives you a practical snapshot of whether your current sleep duration is working for you, regardless of what the guidelines say. Some people genuinely function well on 7 hours. Others need closer to 9. Your daytime alertness is the best indicator.
Weekend Catch-Up Sleep Doesn’t Work
If your strategy is to sleep five or six hours on weeknights and make up for it on Saturday and Sunday, the research is discouraging. A study covered by Harvard Health found that people who cut sleep by five hours during the week and then slept extra on weekends still showed excess calorie intake after dinner, reduced energy expenditure, increased weight, and harmful changes in how their bodies processed insulin. Even though their sleep debt was technically resolved on paper, their metabolic outcomes were similar to people who stayed sleep-deprived straight through the weekend.
This doesn’t mean a weekend lie-in is harmful. It means it can’t undo the damage of chronic short sleep. The more effective approach is to add even 20 to 30 minutes of sleep on weeknights, keep your bedtime and wake time within a consistent window, and protect the conditions that let you fall asleep faster: a cool room, limited screen time before bed, and a predictable wind-down routine.
Is Sleeping Too Much a Problem?
Regularly sleeping more than 9 hours is associated with higher rates of type 2 diabetes, heart disease, and obesity. But the relationship isn’t straightforward. Johns Hopkins Medicine notes that the causal direction likely runs the other way in many cases: underlying conditions like depression, heart disease, or diabetes cause people to sleep longer rather than long sleep causing those conditions. If you consistently need more than 9 hours and still feel unrested, that pattern is worth investigating, not because oversleeping itself is dangerous, but because it often points to something else going on.