While you sleep

Is it normal for oxygen to drop to 88 while sleeping?

By GyroscopeUpdated November 14, 20269 sources

Once, yes. In 350 people with normal sleep studies, the lowest point of the night averaged about 90, and plenty dipped under that. If your lowest point keeps landing under 90 night after night, or someone has seen you stop breathing, ask your doctor about a sleep study.

All of this is about a dip while you’re asleep. Awake and resting, 88 or lower means get medical care now.

How common is a dip to 88?

More common than the number makes it sound. The healthy sleepers’ lowest points averaged 90.4, with a spread (standard deviation) of 3.1 points. If that spread follows the usual bell curve, about 1 in 5 of them dipped to 88 or lower on the night they were tested, and most stayed between about 84 and 97. The same study found sex, race and weight made no difference, and people over 60 ran a little lower.

It’s like the slowest moment of your heart rate at night. Everyone has one, it’s lower than you’d guess, and one night’s lowest says little on its own.

Why does your watch catch it?

An Apple Watch measures now and then while you’re still, and it only measures in sleep if Track Sleep is on. In the big Apple Watch study, background measurements were tried about every 30 minutes. The lowest point it shows you is the lowest of the moments it caught, and a night with more measurements has more chances to catch a low one.

Watches also get less exact down here. Below a true 88, an Apple Watch Series 7 was off by about 6 points, more often too high than too low, in 9 young adults breathing controlled low oxygen. Treat the exact number loosely, and look at whether it repeats. The sleep lab measured all night with a medical pulse oximeter, so its lowest points and your watch’s lowest point aren’t quite the same measurement.

What can push one night down to 88?

• Drinks. In 14 trials, alcohol lowered the night’s lowest point by about 1.25 points. In a 1981 study of 20 men with no symptoms, one evening of alcohol nearly doubled the oxygen dips, and they stayed raised the next night with no more alcohol (alcohol and blood oxygen).
• Sleeping higher than usual. A mountain trip lowers every night you’re up there.
• Sleeping on your back, if your airway narrows in sleep (back sleeping).

When is 88 more than a dip?

When it keeps coming back, or other signs come with it. The ones doctors ask about are loud snoring, someone seeing you stop breathing in your sleep, feeling sleepy in the day even after a full night, and high blood pressure. If someone has seen you stop breathing, ask your doctor now and skip the three-night test. If your lowest point drops under 80, talk to your doctor too, because that’s well under what healthy sleepers reach.

The card below gives you three dated nights to fill in. On the fourth morning it tells you whether you had one low night or a pattern to bring to your doctor.