How Bad Is It Really to Use Blue Light Before Bed?

Your face is washed, teeth are brushed and pajamas are on. With good intentions, you grab the novel on your nightstand and crawl into bed, fully intending to crack open the cover. Then, suddenly — almost as if by magic — you've spent a full half hour scrolling on your phone, book resting beside you.

If that sums up your usual evening routine, you're not alone. We're all well aware that an hour (or was it two?) before bed, all electronics should be off and charging, but social media remains tempting. When you spend the night tossing and turning, you may wonder if the blue light from your phone is at fault.

But is blue light before bed to blame for a sleepless night? And how bad is it really for your sleep? Here, we'll break down how exactly blue light affects your body and what happens when you spend your final waking hours scrolling the feed.

Before we dive into blue light, a quick recap on the science behind how we see light.

All light is made up of red, yellow, orange, green, blue, indigo and violet light, each with a different wavelength, according to Prevent Blindness, a consumer advocacy organization for eye health and safety. Different shades of light have different amounts of each color. For instance, light that appears white can have a larger blue light component.

Different shades on the spectrum affect your body in different ways, per Harvard Health Publishing. When you're exposed to them during the day, blue wavelengths can increase your alertness, reaction time and even your mood.

"Too much blue light exposure at night may make it harder to go to sleep."

Sunlight, fluorescent light, LED light, television screens, tablets and smartphones are all sources of blue light, says Christopher Zoumalan, MD, an eyelid surgeon who is board-certified by the American Board of Ophthalmology.

The amount of blue light you get from a cell phone is less than the amount from the sun. But the length of time you look at the screen may affect your sleep, while the phone's proximity to your face may lead to eyestrain.

There's a reason experts warn about the harmful effect of blue light on your sleep.

The logic is simple: Blue light is like sunlight, which sends signals to your body that it's time to wake up. So, to assume that the blue light on your phone affects your sleep isn't a very far stretch. That assumption is pretty accurate, according to Dr. Zoumalan.

"Blue light can certainly affect your circadian rhythm, which is our natural sleep and wake cycle," he says. "During the daytime, blue light keeps us awake and stimulates us, but it also affects our sleep cycle if we are exposed to blue light before going to bed. Too much blue light exposure at night may make it harder to go to sleep."

Exposure to blue light affects your production of melatonin, a natural hormone that the body releases when it gets dark outside, according to the National Sleep Foundation. As the levels of melatonin in your blood rise, your body feels less alert and more sleepy. The hormone levels stay elevated for about 12 hours and naturally decrease in the morning.

But your body can't tell the difference between sunlight and a TV or computer screen. So, watching a late-night episode of your favorite show can actually push back your melatonin production, skewing your circadian rhythm and making it more difficult to fall asleep.

In an effort to preserve your evening electronic use, you may be wondering how much blue light it actually takes to affect your sleep.

You'll have different reactions depending on the light's wavelength, which is measured in nanometers (nm). Shorter wavelengths suppress melatonin more than longer wavelengths, making it potentially more difficult to fall asleep, per an older March 2001 study in ‌Chronobiology International‌.

Even dim lights, such as a bedside lamp, can have damaging effects on your sleep.

There's no hard-and-fast rule as to the amount of blue light that affects melatonin production. But note that all blue light only exists somewhere approximately between 450 nm and 490 nm, which is a short wavelength, according to Arizona State University.

What do these numbers look like in real life? Even dim light can have damaging effects on your sleep, according to Harvard Health Publishing. Most table lamps, for instance, exceed the amount of light needed to push back your body's melatonin production at least a little. So, the more you can limit your exposure to any kind of light before bed, the better.

In addition to its effect on your sleep, blue light can strain the eyes (also known as digital eyestrain). There's no evidence that the blue light from screens or electronic devices can cause permanent damage to eyes, per Harvard Health Publishing. However, staring too long at screens can cause your eyes to become fatigued, dry and generally uncomfortable, according to the American Academy of Ophthalmology.

You may be disappointed to hear that those fancy blue light-blocking glasses you saw online probably won't do much to help matters when it comes to digital eyestrain. That's because other factors — like blinking less as you stare at your monitor — are the main source of digital eyestrain, and not the blue light, according to the Cleveland Clinic.

And when it comes to these glasses and sleep health, over the years, research has been back and forth. More clinical trials of blue light-lock blocking glasses to determine whether or not they actually benefit your sleep, according to a January 2019 ‌Cochrane‌ review. Recent research points to blue light-blocking glasses potentially having sleep-related benefits, though. For instance, one small January 2018 study in the ‌Journal of Psychiatric Research‌ found that wearing this type of glasses in the hours preceding bedtime reduced insomnia-related symptoms. And, a more recent systematic review found that there was evidence that blue light-blocking glasses may help cut the time it takes for shift workers or people with sleep disorders or jet lag to fall asleep, according to results published in ‌Chronobiology International‌ in October 2021.

For some, switching electronics to "night mode," which minimizes the amount of blue light emitted by the devices, may have a minimal benefit, Dr. Zoumalan says. But more research is needed to know if it's truly effective, and nothing beats simply switching your devices off at least one hour before bed.

If you find yourself struggling to fall asleep or tossing and turning throughout the night, it can't hurt to limit your blue light exposure from all that scrolling or from watching your favorite show late at night. But some simple lifestyle tweaks can also help with other sleep-sabotaging issues.

Now that you're familiar with just how damaging blue light can be, it's time to implement some discipline into your bedtime routine. Here's how:

Developing a healthier sleep routine starts with consistency, according to the National Sleep Foundation. Going to sleep and waking up at the same time every day can help regulate your internal clock. Over time, this will make it easier to fall asleep each night.

Give yourself an electronic curfew, too.

As the sun goes down, dim the lights in your home, using as little bright light as needed, the National Sleep Foundation recommends. You'll also want to curtail your use of electronics at night, Dr. Zoumalan says, especially in the hour or two before your head hits the pillow.

You can enable an automatic night mode on your phone, but ideally, you'll want to stop using electronics before bed altogether.

Aside from your electronics, add some relaxing elements to your nighttime routine. Scheduling some relaxing stretching or meditation can help you wind down, the National Sleep Foundation suggests. Avoid alcohol, cigarettes and caffeine close to bedtime and keep your dinner light.