Best light color for sleep: is red light better?

If you need some light at night, its color matters, its brightness matters more, and darkness beats both. That is the short version of what the research on light and sleep shows. Red and amber light disturb the body clock less than blue or cool white light, but even red light made sleep worse than darkness in a recent sleep laboratory study.

The short answer

• While you sleep, keep the room as dark as you can. An international expert consensus recommends a sleeping environment that is as dark as possible.
• If you need light to see at night, keep it dim, warm and low. Amber, orange or red light near the floor lets you find your way without lighting up your eyes.
• In the evening, dim and warm your lights. The same consensus recommends low light for at least three hours before bed.
• By day, get plenty of bright light. Daylight is best.

Why the color of light matters

The eye has light-sensitive cells that help set the body clock and control melatonin, the hormone that rises in the evening before sleep. These cells respond most strongly to blue light.

• In a study of 72 healthy volunteers, researchers tested light from violet to orange at night and measured how much each color suppressed melatonin. The strongest effect came from blue light between 446 and 477 nanometers.
• In another study, blue light at 460 nanometers suppressed melatonin twice as much as green light at 555 nanometers delivered at the same intensity, and it shifted the body clock twice as far.

That is why a standard light meter can mislead. Ordinary lux readings are weighted to how bright light looks to us, and our eyes see green and yellow as brightest. The body clock cares more about blue.

How bright is too bright

A 2022 consensus of sleep and light researchers set out targets using a measure of how strongly light acts on those clock-setting cells, called melanopic equivalent daylight illuminance and measured at the eye.

Few people own a meter that reads these units, so treat the table as a direction: bright days, dim evenings, dark nights. For a sense of scale, in a study of 116 young adults, ordinary room light below 200 lux in the hours before bed delayed the evening rise of melatonin in 99 percent of participants and shortened the night’s melatonin by about 90 minutes, compared with dim light below 3 lux.

Does red light help you sleep?

Red light is the least disruptive color, and that is where the idea of red light for sleep comes from. The best direct test we found is less flattering.

In a 2023 study, 57 adults with insomnia and 57 healthy adults spent an hour before bed under red light, white light or darkness, then slept in a laboratory while researchers recorded their sleep. The red light was set at about 75 lux, a normal level for bedroom activity.

• Red light made people in both groups feel more alert, and it raised anxiety and negative mood.
• Compared with darkness, healthy adults under red light slept less and had more brief arousals. People with insomnia took longer to fall asleep and spent more time awake during the night.
• Compared with white light, red light helped in one way: both groups fell asleep faster after red light, and people with insomnia also slept longer.

So red light was better than white light and worse than darkness. The practical message is to choose red or amber when you need light at night, and to keep it dim, rather than adding red light to help you sleep.

Red light therapy is a different thing. In a small 2012 study, 10 athletes received 30 minutes of red light from a therapy device each night for 14 days and reported better sleep and had higher blood melatonin than 10 athletes who received no light. Without a sham treatment for comparison, that study cannot tell us much, and it says nothing about night lights.

Sleeping with the lights on

Light while you sleep does more than wake you up.

• Melatonin. In the room light study above, ordinary room light during the usual hours of sleep suppressed melatonin by more than half in 85 percent of trials.
• Heart rate and blood sugar. In a 2022 laboratory study, healthy adults who slept one night under overhead light at 100 lux had a higher heart rate during the night and more insulin resistance the next morning than when they slept in dim light below 3 lux.
• Long-term health links. A study of 43,722 women found that sleeping with any artificial light in the room was linked with higher rates of obesity, and the authors suggested it may be a risk factor for weight gain. In 552 adults aged 63 to 84 who wore light-measuring devices for a week, any light during the darkest five hours of the night was linked with higher rates of obesity, diabetes and high blood pressure. These studies show associations and cannot prove that the light caused the problems.

To cut the light while you sleep, switch off the TV or use its sleep timer, cover or turn away devices with bright standby lights, and deal with light from outside with blackout curtains or an eye mask.

Screens in the evening

In a 2015 study, adults who read on a light-emitting e-reader before bed, compared with a printed book, took longer to fall asleep, felt less sleepy in the evening, had less melatonin, had a later body clock and were less alert the next morning.

If you use a phone or tablet in the evening, turn the brightness down and switch on a warmer night mode, which reduces the blue part of the light. The simplest step is to put the screen down earlier.

Do amber glasses help?

Two small trials suggest amber lenses can help some people.

• Fourteen adults with insomnia symptoms wore amber lenses or clear lenses for two hours before bed for a week each. Their insomnia scores improved with the amber lenses.
• Twenty adults wore amber glasses or yellow glasses that blocked only ultraviolet light for three hours before bed. The amber group reported better sleep quality after the study than the control group.

Both trials were small and tested deep amber lenses. The results may not apply to clear lenses sold for screen use.

How to choose a night light

1. Pick a warm color. Amber, orange or red affects the body clock least. Avoid blue and cool white.
2. Use the lowest brightness that works. You need enough light to move safely, nothing more. A dimmer helps.
3. Place it low. A light near the floor or under the bed lights your path without shining into your eyes. The expert targets are measured at the eye, so light aimed away from your face counts for less.
4. Let it switch itself off. A motion sensor or timer keeps the room dark while you are asleep.
5. Keep it out of your line of sight from the pillow.

Calm Eden, which shares Lumuwala’s owner, sells a Glimmer Motion Sensor Night Light. The listing describes a warm glow, a sensor that detects movement from 3 to 5 meters away, automatic switch-off 20 seconds after you pass, and no wiring. It did not state the brightness or color temperature when we checked, so we cannot say how it compares with the targets above. We have not tested it.

If you also want a lamp by the bed rather than a plug-in night light, Calm Eden’s bedside lamp guide covers lamp height, lumens, warm light, shades and controls. Calm Eden is owned by the same company as this site, so read it as an owned-store guide.

Blackout curtains and eye masks

If light comes in from a street lamp, early sunrise or a partner’s reading light, blocking it may help. In a 2023 study, 94 adults aged 18 to 35 wore an eye mask every night for a week and spent another week without light blocked. With the mask, they did better on a memory task and a test of alertness. A 2015 Cochrane review of sleep in intensive care units found low-quality evidence that earplugs, eye masks or both may help patients sleep, so the evidence outside a normal bedroom is limited.

A mask needs to be comfortable enough to stay on. Blackout curtains or blinds avoid anything on your face, and they also cut early morning light.

When light is not the whole story

If you still wake in the night, our guide to waking at 3 a.m. covers what to note and when to talk to a clinician. Noise and heat wake people too, so check our guides to white, pink and brown noise and the right bedroom temperature. If poor sleep continues for weeks or affects your days, speak with a clinician. Light changes are not a treatment for insomnia or other sleep disorders.