What's a normal blood oxygen for my age?
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About the same at every adult age: 95 to 100 awake and resting. In 33,080 Apple Watch wearers, 20 more years of age lowered the typical night by under 1 point, and living a kilometre (3,300 feet) higher lowered it by more.
What we’d do
Use the same lines at every age. Awake and resting, 92 or lower is a call to your doctor whether you’re 30 or 80. Judge a low night against your own usual nights on the same device, and don’t put a low number down to your birthday.
How much does age change it?
Very little. The Apple Heart and Movement Study collected about 72 million blood oxygen values from Apple Watch Series 6 wearers in 2021, and its researchers worked out how much each thing moved the typical number. Each year of age took about 0.04 points off the night average and 0.03 off the day. Twenty years comes to under a point at night.
Here’s the typical range by age, at sea level, for someone with a BMI of 25:
| Age | Typical night average | Typical day |
|---|---|---|
| 20 | 94.4 to 99.2 | 95.0 to 99.5 |
| 30 | 94.0 to 98.8 | 94.7 to 99.2 |
| 40 | 93.5 to 98.4 | 94.4 to 98.9 |
| 50 | 93.1 to 97.9 | 94.1 to 98.6 |
| 60 | 92.7 to 97.5 | 93.8 to 98.3 |
| 70 | 92.2 to 97.1 | 93.5 to 98.0 |
| 80 | 91.8 to 96.7 | 93.2 to 97.6 |
Each range is where about 95 in 100 watch wearers like you sit, if the spread follows the usual bell curve. These come from one watch model in US wearers, and they describe a person’s usual nights, so a single night can land outside them.
A sleep lab study found the same small slide. In 350 people with normal sleep studies, those over 60 ran a little lower than younger people, and sex, race and BMI made no difference.
What moves it more than age?
Where you live. In the same watch study, each kilometre of home elevation took about 1.2 points off the night average, as much as about 27 years of getting older. A typical 40-year-old in Denver sleeps at about 94.1. A typical 80-year-old at sea level sleeps at about 94.2.
Age works like a slow leak in a tire, a little lower each year. Moving from the coast to the mountains is more like letting out a good puff of air at once. Weight moves it a little too: each point of BMI took about 0.06 points off a typical night, so 10 points of BMI comes to about half a point.
Does a lower number at 70 mean something’s wrong?
Not if it’s inside the typical range for your age. A 70-year-old whose watch shows a night average of 93 is inside the range above, and so is a 20-year-old at 95. What counts at any age is the same: the awake lines from MedlinePlus (95 to 100 normal, 92 or lower call your doctor, 88 or lower get care now), and a pattern of low nights against your own usual ones.
The tool below puts your age, your elevation and your device together, so you can see which one moves your number most. Children’s numbers differ, so ask your child’s doctor.
3 sources
- MedlinePlus, Pulse Oximetry, US National Library of Medicine, updated September 12, 2024medlineplus.gov
- Shapiro I and others, Pulse oximetry values from 33,080 participants in the Apple Heart and Movement Study, npj Digital Medicine, 2023pmc.ncbi.nlm.nih.gov
- Gries RE and Brooks LJ, Normal oxyhemoglobin saturation during sleep: how low does it go?, Chest, 1996europepmc.org
