Does blue light from your phone keep you awake?

Key takeaways

• Verdict: partly true. Blue light delays melatonin and the body clock more than other colors of light do. But in studies of people using ordinary phones and tablets, the screen’s light made little or no measurable difference to their sleep.

• Brightness and time count as much as color. In one lab study, a tablet’s warm night setting barely changed its effect on melatonin while the screen stayed at full brightness.

• Your room lights have an effect too. Ordinary indoor lighting in the evening is enough to hold back melatonin in many people, and some people are about 50 times as sensitive to it as others.

• The phone itself may be the bigger problem. More time on screens in bed goes with less sleep, whatever the color of the light, and exciting games or messages late at night can keep you up.

• Blue light glasses are unproven for sleep. A Cochrane review found the evidence on sleep too weak to say whether they help.

Where the blue light idea comes from

The idea has real science behind it. In 2002, researchers studying rats found a set of cells in the retina that respond to light on their own, separate from the rods and cones we see with. These cells report to the brain’s master clock, which controls when you make melatonin, the hormone that rises in the evening as you get sleepy.

The cells are most sensitive to blue light. In a 2003 lab study, six and a half hours of blue light suppressed melatonin about twice as much as the same amount of green light, and shifted the body clock about twice as far.

Phones, tablets, and laptops have LED screens, and when researchers measured an iPad, an iPhone, and a Kindle, all three gave off blue-heavy light. Put those findings together and you get the advice most people have heard: the blue light from your phone keeps you awake. The NIH says light from electronic devices at night “can confuse biological clocks,” and the NHS advises putting screens away for an hour before bed.

What the lab studies show

Under lab conditions, screen light can delay melatonin, if there’s enough of it. In a 2013 study, 13 people used tablets at maximum brightness. After one hour, their melatonin wasn’t significantly suppressed; after two hours, it was.

A 2023 study went further. It gave 72 men three and a half hours of screen light before bed, at different settings. At the brightest setting with the most clock-stimulating light, compared with the dimmest setting with the least, they took about 50% longer to fall asleep, and their melatonin started rising about an hour later. (One author holds patents on display and lighting technology, and two others are named on related patent applications.)

Those are long sessions at high brightness, though, and the room light around the screen has a big effect of its own. In a 2019 study of 55 young adults, room lighting of about 25 lux, no brighter than typical indoor lighting at night, was enough over five hours to cut the group’s melatonin by half. People varied enormously: the most sensitive person’s melatonin was halved at 6 lux, the least sensitive person’s at 350.

What happens with real phones

Studies that look at ordinary screen use find much smaller effects.

• An hour on a tablet: In a 2014 study, 16 teenagers spent an hour before bed on a bright tablet, a dim one, or one with a blue light filter. None of the three changed how quickly they fell asleep or their sleep stages.

• A week with Night Shift: A 2021 trial split 167 young adults into three groups for a week: iPhone Night Shift on, Night Shift off, or no phone in the hour before bed. Their sleep, measured with wrist trackers, didn’t differ between the groups.

• An expert review: In 2024, a 16-person expert panel reviewed the research for the National Sleep Foundation. They agreed that screen use, and what’s watched or done on screens before bed, harms sleep in children and teenagers. They couldn’t reach agreement that the light from screens harms sleep at any age, and wrote that its effects were typically small or came from lab setups unlike everyday use.

Why your phone may keep you up anyway

If the light isn’t the main problem, the phone can still be. Three things seem to do more harm than the color of the screen.

Time in bed on the phone. In a 2025 survey of 45,202 Norwegian students, each extra hour of screen use in bed went with 59% higher odds of insomnia symptoms and 24 minutes less sleep. Social media wasn’t any worse than other screen use. It’s a survey, so it can’t show which came first: people who can’t sleep may also reach for their phones.

What’s on the screen. In a 2005 study of seven men, an exciting video game before bed made people take longer to fall asleep and cut their REM sleep, while the brightness of the screen made no difference. It isn’t simple, though. When 50 young adults binge-watched a suspenseful series in a 2023 sleep lab study, they fell asleep slightly faster than after a calm one.

Messages after lights out. In a 2016 study of 844 adults, texting and calls after lights out were linked to worse sleep. A phone that buzzes in the night wakes you whatever color its screen is.

Do night mode and blue light glasses help?

Night mode shifts the screen toward warmer colors. In a 2019 study of 12 adults using an iPad at full brightness for two hours, the warmest Night Shift setting suppressed melatonin by 12% and the coolest by 19%, which wasn’t a significant difference. The researchers suggested that turning the brightness down, or keeping use to about an hour, would do more than changing the color. We found no good studies of dark mode and sleep.

Blue light glasses have weak evidence behind them. A 2023 Cochrane review of 17 trials found they may not reduce eye strain, and called their effect on sleep indeterminate: of six trials that measured sleep, three found an improvement and three didn’t. All six sleep trials tested strongly tinted amber, orange, or red lenses, not the nearly clear ones sold for screen use, and even those gave mixed results. In a small 2018 trial, 14 adults with insomnia who wore amber glasses for two hours before bed slept longer over a week.

As for the other common worry, the American Academy of Ophthalmology says there’s no scientific evidence that blue light from devices damages your eyes, and it doesn’t recommend blue light glasses for computer use.

What to do instead

• Turn the brightness down in the evening. It does more than changing the color. Use night mode too if you like it; it won’t hurt.

• Dim the room, not only the phone. Lamps instead of overhead lights for the last hour or two before bed.

• Get bright light during the day. In a 2002 study, 12 people who spent a week getting about four hours of bright light a day, outdoors and from light boxes, were less sensitive to light at night than after a week wearing dark goggles outdoors.

• Keep scrolling out of bed. If you read on your phone, do it somewhere else, and put it down when you’re sleepy.

• Silence it overnight. Turn on Do Not Disturb, or charge the phone outside the bedroom so messages can’t wake you.

If light in the bedroom is waking you early, see whether blackout shades are worth it. And if you’re awake in the small hours reaching for your phone, read why you might wake up at 3am.

Verdict: partly true

Blue light really does affect the body clock more than other light, and enough bright screen time in a dark room can delay melatonin. But in everyday use, the light from a phone makes only a small difference to sleep, and filters and glasses haven’t been shown to fix much. The bigger problems are how long you spend on the phone in bed, what you’re doing on it, and messages that wake you up. Dim the screen and the room, and put the phone down earlier.

Frequently asked questions

Does night mode help you sleep?

Probably not much on its own. In studies, warmer screen colors made little difference to melatonin or sleep while brightness stayed high. Turning the brightness down and using the phone for less time before bed are likely to help more.

Are blue light glasses worth it for sleep?

The evidence is weak. A Cochrane review couldn’t say whether they improve sleep. Strongly tinted amber or orange glasses helped in some small trials and not in others, and the near-clear lenses sold for screens haven’t been tested for sleep.

How long before bed should I stop using my phone?

The NHS suggests an hour. There’s no exact cutoff in the research, but less screen time in bed is consistently linked to more sleep.

Does blue light damage your eyes?

According to the American Academy of Ophthalmology, there’s no scientific evidence that blue light from phones and computers damages the eyes. Long screen sessions can cause eye strain, which rest breaks help with.

Is it better to read a paper book before bed?

A paper book under a dim lamp gives off less light and doesn’t buzz with messages, so it’s an easy swap. If you read on a device, turn the brightness down.

Does dark mode help you sleep?

We found no good research on dark mode and sleep. It does cut the amount of light coming from the screen, so it’s unlikely to hurt.