There’s no debating that we need sleep. It's crucial for our mental and physical health, quality of life, and overall safety, according to the National Heart, Lung, and Blood Institute. Proper sleep not only leaves you feeling refreshed and ready to take on the day, it improves learning, helps the heart and blood vessels repair themselves, promotes a healthy balance of hunger hormones, and aids the immune system.

For most people, seven to nine hours of sleep each night is sufficient, though your age, activity level, and health can shift that target in either direction, according to the Sleep Foundation.

And while sleep deprivation is a widespread problem (considering all the aforementioned health functions of sleep), sleeping too much can be cause for concern as well. The Sleep Foundation defines oversleeping as sleeping more than nine hours in a 24-hour period.

You’ve likely done that before when recovering from a stressful work week or a busy travel weekend or if your body was fighting a cold. In those cases, oversleeping is normal, says Safia Khan, MD, a specialist in sleep disorders and an assistant professor in the department of family and community medicine and the department of neurology at UT Southwestern Medical Center in Dallas.

“If you're just waking up late just to catch up on your sleep, that's called recovery sleep,” Dr. Khan says. “But when you're doing that habitually and you're sleeping more than eight or nine hours every day, that would be oversleeping.”

Oversleeping typically indicates something else is going on, such as an underlying sleep disorder or another medical condition. “Oversleeping is more of a symptom than a diagnosis,” Khan says.

What Causes Oversleeping

“The most common causes we look at when someone says they're sleeping more than nine hours a night is if it’s a medication effect or a medical, psychiatric, or neurological disorder,” says Ulysses Magalang, MD, the director of the sleep disorders program at the Ohio State University Wexner Medical Center in Columbus. “If those aren’t the reason, it could be a sleep disorder.”

According to the Sleep Foundation and Johns Hopkins Medicine, oversleeping most often occurs with the following underlying health conditions:

• Obesity
• Cardiovascular disease
• Diabetes
• Restless leg syndrome
• Bruxism (teeth grinding or clenching)
• Chronic pain
• Sleep disorder (such as sleep apnea, insomnia, or narcolepsy)
• Hypothyroidism
• Depression or anxiety

A study published in December 2018 in the European Heart Journal, for example, found that sleeping more than six to eight hours per day (including naps) was linked to higher risk of death from heart disease, according to survey data from more than 116,632 adults from 21 countries.

How common is oversleeping? According to research published in Annals of Neurology, 8.4 percent of the nearly 20,000 participants reported oversleeping (sleeping for nine or more hours per day). People with a mood disorder were three to 12 times more likely to oversleep and two to four times more likely to report a poor quality of life compared with those who slept less.

Khan says oversleeping can also be attributed to hypersomnia (or excessive daytime sleepiness), delayed sleep phase syndrome, an abnormal balance of hormones, Parkinson’s, or dementia.

Signs You’re Sleeping Too Much

While regularly sleeping more than nine hours per night is one red flag, it’s not the only signal to look out for. And sleeping more than nine hours a night isn’t always cause for concern.

Some people naturally need more sleep than others. “About 2 percent of the population are ‘long sleepers’ who require between 10 to 12 hours of sleep nightly on a regular basis,” says Shanon Makekau, MD, the chief of pulmonology and the sleep medicine director at Kaiser Permanente in Honolulu.

For these people, oversleeping is normal. “Trying to impose a typical seven- to nine-hour sleep schedule on such people can be detrimental and effectively results in a sleep debt,” Dr. Makekau says. If you regularly sleep longer than nine hours per night, but wake up feeling refreshed and rested, you’re likely a long sleeper.

If you don’t feel refreshed when you wake up after sawing logs for sufficient hours, there could be a problem. Khan says oversleeping is generally accompanied by symptoms of tiredness during the day, including grogginess, headache, decreased energy, and mood changes.

Why Oversleeping Is Risky

“While consistently getting less than the recommended amount of sleep has been associated with multiple adverse health outcomes, sleeping more than nine hours per night regularly may also be detrimental,” Makekau says.

She says oversleeping can lead to:

• Increased fatigue and low energy
• Decrease in immune function
• Changes in stress response
• Increased risk of chronic diseases, such as heart disease, diabetes, and obesity
• Increased risk of death

What to Do if You Suspect You’ve Been Oversleeping

The Cleveland Clinic suggests trying to get your sleeping back on track yourself by:

Avoiding the snooze button

Waking up at the same time every day — weekends included

Embracing natural light when you wake up and avoiding it close to bedtime

If you still find yourself oversleeping regularly after making these changes, schedule a visit with your primary care physician. Dr. Magalang says doctors will typically employ a process of elimination to rule out conditions in order to determine the underlying issue.

Your doctor will likely start by performing a physical exam, reviewing medications that may affect sleep, and discussing further testing, including blood work, Makekau says.

He or she will want to know details about your sleep habits. Khan suggests keeping a sleep diary for at least two weeks before the appointment and noting how much you’re sleeping and the quality of that sleep.

Then, he or she may give you a referral to a sleep clinic or recommend you have a sleep study done, Khan says. A sleep study can help rule out sleep disorders, according to Johns Hopkins Medicine.