What Your Screen Is Actually Doing
The light coming off your screen carries blue and green wavelengths, and your brain treats those as a daytime signal. In response it holds back melatonin, the hormone that makes you feel drowsy Gooley et al., 2010. The longer you scroll, the longer your body stays convinced it's still the middle of the day.
It isn't only the phone. The lamp on your nightstand and the light overhead add to it, since ordinary indoor light in the evening is enough to blunt melatonin Gooley et al., 2011. But the screen is the one a few inches from your face for an hour straight, so it's the main source.
You Don't Have to Give Up the Hour
The usual advice is to just stop. An hour of no screens before bed. But that last hour is the one that's actually yours, and giving it up is a big ask. Realistically, you're going to scroll.
So the better question isn't how to use your phone less. It's how to keep the evening you like while taking the daytime signal out of it.
Change the Light, Not the Habit
Red lenses filter the blue and green light before it reaches your eyes. Night mode can't match that. It warms the color of your screen but doesn't dim it, and in a controlled study that warming didn't meaningfully reduce melatonin suppression Nagare et al., 2019. It also leaves green mostly untouched and does nothing about the lamp beside you.
Put them on an hour before bed and change nothing else. Scroll, stream, whatever your evening is. The blue and green light just doesn't reach your eyes, so it can't tell your brain it's daytime.
None of this sets your bedtime for you. But the light is the biggest part you can actually control, and the only one you can switch off without changing your evening at all. Red is the tint that filters the most of it, which is the whole case for red over amber or clear.
Common Questions
Do I have to stop looking at my phone before bed?
No. That's the whole reason to filter the light instead. The problem is the blue and green light your screen gives off, not the fact that you're awake and entertained. Handle the light and you keep the phone.
Is it really the light, or am I just staying up too late?
The light is the big one. It's what makes your brain think it's still daytime, so the same bedtime hits differently after an hour on a bright screen. Filter it and your evening stops working against you.
Does night mode do the same thing?
Not really. It warms the screen but doesn't dim it, and studies haven't found it makes a meaningful dent in melatonin suppression. It also skips green and ignores the lamp beside you. Red lenses filter the full range, on the screen and in the room.
When should I put them on?
About an hour before bed, then just carry on. Scroll, watch, whatever your evening is. The lenses do their part while you do nothing different.