How Light Can Improve or Disrupt Your Sleep Quality

March 30, 2026

An overhead view of a woman in bed wearing a sleeping eye mask

Sleep is critical to health, but how much you get and how restful it is depends on many factors, including the amount of light and darkness you’re exposed to throughout the day. Light plays an important role in regulating the quality of your sleep and how you feel when you wake up.

“Morning light tells your brain it is daytime and you need to be awake and alert,” says Eileen Wong, MD, a sleep medicine expert at University Hospitals. “You want less light at night, so it’ll be easier to fall asleep.”

The Importance of Getting Light During the Day

Just as going to bed and waking up at the same time each day can improve sleep quality, getting light first thing each morning can also benefit your natural sleep-wake cycle. This is because your body’s 24-hour biological clock tends to be the most sensitive to light within the first hour of your usual wake-up time and during the last couple hours before you go to bed. Being exposed to light during these periods will influence sleepiness and wakefulness.

The type of light, along with when and how long you’re exposed to it, also makes a difference. “You need morning sunlight for at least 15 minutes to help reinforce to your brain that it’s time to be awake,” says Dr. Wong. If it’s cloudy or foggy out, she suggests a session of bright light therapy with a light box for 30 minutes right after waking up, or you can use a light therapy visor or glasses.

“If using the light box, stay about 1 to 1.5 feet from it to get optimal effect,” says Dr. Wong. “The most important thing is choosing a light box with 10,000-lux full-spectrum white light.”

Problems With Light at Night

Blocking out light at night helps people get better sleep. It’s why pulling down the shades and turning off the lights has become such a common bedtime ritual. Yet in many modern bedrooms, there are multiple sources of light that often remain, from cell phones, electronics and little lights on smart switches and fire alarms. Even at very low levels, such light can disrupt sleep.

Part of the problem with being exposed to light at night is that it can affect melatonin levels. Melatonin is a hormone that your body naturally produces. It makes you feel tired. “Production of melatonin in your body is stimulated by darkness and inhibited by light,” says Dr. Wong.

Melatonin levels naturally rise in the evening, and it prepares your body for sleeping by calming and shutting off activity in your brain, she explains. “But it doesn’t necessarily put you to sleep immediately.” If you’re exposed to sources of light close to bedtime, including the blue light from your smartphone, tablet or TV, it can delay the release of melatonin and make it harder for you to fall asleep.

Melatonin supplements can sometimes be used to help people who struggle with sleeping. They’re commonly prescribed for shift workers and those sensitive to jet lag. Melatonin, if being used as a sleep aid, should be taken 60 to 90 minutes before bedtime. But even with a melatonin supplement, Dr. Wong says it’s important to limit light exposure. “You can consider wearing blue-light blockers at night,” she says. “Better yet, turn off devices 1 to 2 hours before you go to sleep.” If you need a little light for safety purposes in the dark, she suggests using a dim, warm-toned light.

Nighttime Light Exposure and Health

Nighttime exposure to light can contribute to an array of health problems. Oftentimes, it triggers insomnia. Research suggests it can interfere with metabolism and make it harder for your body to control blood sugar levels. It may also raise your risk of cancer and diabetes.

“Insufficient sleep leads to a lot of bad health issues,” says Dr. Wong. She points out that getting less than seven hours of sleep has also been associated with higher incidence of:

Mortality
Hypertension
Heart disease and stroke
Alzheimer’s dementia
Impaired immune system
Obesity
Depression

Tips for Better Sleep

Limiting your exposure to light at night and getting more light in the morning is a good start, but there are many other things you can do to improve your sleep and wake up feeling refreshed.

Dr. Wong shares 10 tips for better sleep:

Keep a regular daily activity and sleep schedule. A consistent wake-up time seven days a week is especially important because it stabilizes your biological clock.
Don’t nap during the day unless advised by your doctor. Napping can make it harder to fall – and stay – asleep at night.
Start winding down in the last hour before bed. Try dimming the lights, listening to relaxing music, reading something soothing, doing light stretches or practicing relaxation techniques like deep breathing or mindfulness meditation.
Create a sleep-friendly environment. Keep your bedroom dark, quiet and cool, and use an eye mask, blackout shades, ear plugs or white noise, as needed.
Don’t consume caffeine in the evening. This includes in food, drink or medications.
Avoid heavy meals and alcohol 2 to 3 hours before bed. The same goes for nicotine, if you smoke or vape.
Limit liquids to less than 10 ounces in the evening. Restrict drinking after dinner and urinate right before bedtime.
Go to bed when you’re sleepy. Wait until your eyes are heavy and you feel like you could fall asleep – not just when you’re tired, since it could lead to lighter, more disrupted sleep.
Use the bed for sleep and intimacy only. Don’t watch TV, eat, read, use your phone or laptop or spend time worrying in bed.
Don’t try too hard to sleep, or stay in bed. If after 15 minutes or so, you can’t sleep, get out of bed and do something quiet and relaxing until you feel sleepy.

When to Talk to a Sleep Specialist

If you’re practicing healthy sleep habits and you’ve talked to your primary care doctor about your sleep problems, but are still having trouble sleeping, you may benefit from seeing a specialist. Dr. Wong says it may be time to see a sleep specialist if you are experiencing:

Insomnia (you can’t fall asleep or stay asleep).
Abnormal leg sensations or body movements.
Difficulty breathing while sleeping (snoring, gasping or choking).
Chest pain that wakes you up.
Excessive daytime drowsiness.
Other symptoms related to lack of sleep (low mood, irritability, general malaise, headache or cognitive impairment).