Smartwatches Have Measured Blood Oxygen for Years. But Is This Useful? (2024)

Smartwatches can measure everything from heart rate to sleep quality, but one health metric has become particularly relevant over the past two years: blood oxygen saturation. Two of the world's biggest smartwatch makers, Apple and Samsung, added blood oxygen monitoring to their wearables in 2020. The COVID-19 pandemic also made measuring vitals from home more desirable.

This story is part of Health by the Numbers, CNET's deep dive into how we quantify health.

But the arrival of blood oxygen monitoring in smartwatches also raised questions about how useful this information is without the context of a medical professional. In CNET's review of the Apple Watch Series 6, Vanessa Hand Orellana said she wished the Apple Watch could provide more guidance to accompany blood oxygen readings. (When her levels dropped to 92% overnight, she didn't know whether to be concerned.) Most smartwatches also aren't cleared by the US Food and Drug Administration for blood oxygen measurements and can't be used for medical purposes, making it difficult to understand how these metrics should be interpreted.

Roughly two years later, are blood oxygen readings any more useful than they were in 2020? The answer isn't that simple. Medical experts say measuring blood oxygen throughout the day and under different conditions could unlock insights you won't get with a traditional pulse oximeter. Plus, having more access to health data from home is also usually a good thing.

But these sensors still have shortcomings that can limit usefulness. And smartwatch makers are still figuring out the best ways to incorporate blood oxygen measurements into broader features that give users a complete picture of their overall health.

"We know the science behind them is still not as accurate as the ones that are hospital grade with regard to the way the oxygen is determined," said Dr. Albert Rizzo, chief medical officer at the American Lung Association. "But having said that, they've become useful from the standpoint of patients, or not even people who are medically ill, even well persons, to be able to track another vital sign."

Blood oxygen monitoring's breakthrough

To understand whether measuring blood oxygen levels from your smartwatch is useful, it's crucial to know what this metric means and how it's implemented in today's wearables first. Your blood oxygen level, also known as SpO2, refers to how much oxygen your red blood cells carry. It's considered an important indicator of respiratory health since it signals how well your body is able to absorb oxygen.

Blood oxygen saturation is typically measured through a pulse oximeterthat clips onto your finger. Smartwatches like the Apple Watch measure this by shining a light through your wrist and measuring the light reflected.

If your current smartwatch or fitness tracker can't measure your blood oxygen levels, chances are the next one you buy will. The technology has become a staple in today's wearables and can be found in products from Apple, Samsung, Fitbit, Garmin and Withings, among others.

The Apple Watch Series 6 and Series 7 both measure blood oxygen levels, as do the Samsung Galaxy Watch 3 and Watch 4. Fitbit devices such as its Sense, Ionic and Versa smartwatches and the Charge 4, Charge 5 and Luxe fitness bands can also measure blood oxygen levels overnight during sleep.

But most companies haven't received FDA clearance for their blood oxygen measuring technology. Withings is the exception; the blood oxygen monitor in its ScanWatch and ScanWatch Horizon are both FDA-cleared. Maxime Dumont, Withings' product manager for smartwatches, says the FDA clearance should make its data more trustworthy to doctors.

"We will never replace a doctor, and we are not intended to make any diagnosis with a watch," he said. "But the watch results are reliable for a physician."

Read more: Fitbit and Apple Know Their Smartwatches Aren't Medical Devices. But Do You?

Even though it was possible to take blood oxygen readings from a smartwatch before 2020, the technology had a breakout moment two years ago. As the pandemic overwhelmed hospitals and the healthcare system, there's been more interest in researching how wearables can monitor bodily changes at home.

Devices from Apple, Fitbit, Garmin and Oura have all been used in research examining whether wearable devices can predict disease early by measuring changes in bodily signals like heart rate and temperature. A 2021 study published in Scientific Reports from researchers at the University of Sao Paolo and Centro Universitário FMABC also found the Apple Watch Series 6 to be reliable at gathering SpO2 and heart rate data in patients with lung disease in a controlled environment.

"The massive number of people that the health system had to deal with made it a little easy for health systems to experiment with these non clinical-grade oxygen sensors," said Dr. Nauman Mushtaq, medical director of cardiology at Northwestern Medicine Central DuPage and Delnor hospitals.

How useful are these sensors in smartwatches?

While health sensors in smartwatches show promise in research, some experts are unsure how often these sensors are being used in everyday circ*mstances. "I have had a few patients who have used Apple Watches or similar devices to monitor their blood oxygen levels," said Dr. Ashraf Fawzy, a pulmonologist and critical care physician and Assistant Professor of Medicine at Johns Hopkins University. "But it hasn't been as common as I would have thought."

Regarding regular use, Dr. Mushtaq sees blood oxygen sensors in devices like the Apple Watch as most useful for adding more context regarding overall wellness. In most cases, the average healthy person would experience physical warning signs before experiencing hypoxemia, or low blood oxygen, he said.

"I don't think it, to be honest, does anything that is clinically meaningful for an average person," he said.

That doesn't mean medical experts don't see potential. Smartwatches have a big advantage over traditional pulse oximeters: their position on your wrist all day. Many smartwatches can take background blood oxygen measurements in addition to providing spot checks, meaning they can gather data at different times during the day.

Read more: Apple Watch Series 8 Rumors: More Health Features, New Rugged Version

Fitbit, Samsung, Garmin and Apple devices can monitor blood oxygen levels passively during sleep, unlike a traditional pulse oximeter which is used for taking on-demand measurements. Both Apple and Garmin can also sample blood oxygen levels periodically throughout the day.

But smartwatches are only good at checking SpO2 levels at rest, even when taking scans in the background. (Apple says its background measurements happen when the wearer isn't moving, and Garmin says it takes readings less often if it detects high movement).

Measuring blood oxygen levels during strenuous activities would make these devices more useful since it could help doctors know whether to adjust the amount of oxygen a patient is being prescribed, according to Dr. Fawzy. Dr. Mushtaq also said patients with heart failure or pulmonary hypertension could benefit from seeing whether their blood oxygen levels drop during exercise.

"That can certainly help," said Dr. Fawzy. "Because for some people, their oxygen levels only drop when they're being active and will be normal when they're sitting quietly."

Health metrics are most useful when put in context, whether it be blood oxygen levels or how many steps you've taken. The numbers and charts only matter when you know how to put them to good use.

"Ultimately, consumers aren't buying sensors," Julie Ask, vice president and principal analyst at research firm Forrester, said in a previous interview with CNET. "They're not buying data. Consumers are buying what they hope is help achieving an outcome."

Smartwatches Have Measured Blood Oxygen for Years. But Is This Useful? (3)

So what kind of context do smartwatches need to provide to make blood oxygen readings more useful? Some companies are trying to answer that question by weaving SpO2 results into other features and in-app wellness reports to better understand your overall health. Samsung, for example, incorporates SpO2 measurements into its sleep coaching feature on the Galaxy Watch 4 to help you make sense of your sleep patterns, according to a Samsung representative. Withings uses blood oxygen levels as one of the metrics it analyzes when determining breathing disturbances, along with heart rate and motion.

Phil McClendon, the manager of Garmin's wellness product management team, couldn't comment on future plans when asked whether SpO2 measurements would be factored into other health insights. But he pointed to Garmin's Health Snapshot as an example of the company's approach to making health data more meaningful.

Read more:How WatchOS 9 Is Paving the Way for the Apple Watch's Future

Health Snapshot compiles various metrics (including heart rate, blood oxygen, heart rate variability, respiration and stress) to provide a high-level view of your cardiovascular status. McClendon said the feature helps people quantify changes that may be happening in their bodies during abnormal events.

"So maybe they're having a panic attack, and they're like 'I want to record this thing and export the PDF to take to my healthcare provider," he said as an example.

Right now, the biggest benefit of measuring blood oxygen levels from your smartwatch is learning what's considered normal for your body. Even though smartwatches aren't meant for medical diagnosis, it's another signal you can take to your doctor if you're not feeling well or notice a bodily change.

"Whatever device you're using, compare it to your baseline, use it as a trend monitor so that you know that you're off from your baseline," said the American Lung Association's Dr. Rizzo. "It may allow you to change what you're doing or seek help sooner than you otherwise would."

Smartwatches Have Measured Blood Oxygen for Years. But Is This Useful? (2024)


Smartwatches Have Measured Blood Oxygen for Years. But Is This Useful? ›

Signals such as heart rate, body temperature, physical activity and oxygen levels are usually not enough to diagnose a disease, but the measurements are still useful in assessing overall health, or for monitoring recovery after surgery, Snyder said. He stressed that smartwatches are not a replacement for a doctor.

Can a smart watch accurately measure blood oxygen? ›

You Can Measure Blood Oxygen Saturation with a Smartwatch

You'll still need FDA-approved pulse oximeters to take medically accurate measurements. Many companies make medical devices such as these for use at home. You simply clip it on your finger to measure your blood oxygen saturation.

Can we trust the oxygen saturation measured by consumer smartwatches? ›

The accuracy of smartwatches is less than the wearable pulse oximeter because both the light-emitting sensor and receiving sensor are on one side, which neglected the transmitting light, thus affecting the accuracy of the readings.

How reliable are smart watch readings? ›

Smart watches generally struggle to accurately track metrics like blood pressure and the quality of your sleep. Step count is relatively accurate among most wearables, and can quite reliably measure how far you've run under optimal conditions.

Which is better oximeter or smartwatch? ›

Smartwatch vs.

If you're wondering whether a pulse oximeter or smartwatch is better for SpO2 reading, the answer may surprise you. While both devices can approximate your blood oxygen saturation levels, pulse oximeters are generally more accurate.

How does my watch know my blood oxygen level? ›

The Blood Oxygen feature on Apple Watch measures SpO2 using conventional pulse oximetry methods: It shines red and near-infrared (IR) light into blood-perfused tissue, detects and processes the reemitted light photo-signals into respective photoplethysmograms (PPGs) that track the heartbeat-induced pulsations, ...

How accurate is blood oxygen on Fitbit? ›

The data provided by Fitbit SpO2 is intended to be a close estimation of your blood oxygen saturation levels, but may not be precisely accurate. You should not use or rely on Fitbit SpO2 for any medical purposes.

What is a normal oxygen saturation level by age? ›

Oxygen saturation levels (SpO2) between 95 to 100 percent are considered normal for both adults and children (below 95% is considered abnormal). People over 70 years of age may have oxygen levels closer to 95%. Normal oxygen saturation levels (SpO2) are between 95 to 100 percent for both adults and children.

What is the most accurate measure of oxygen saturation? ›

An arterial blood gas test is more invasive and painful than using a pulse oximeter, but it's a more accurate way to measure oxygen and carbon dioxide in your blood as well as the balance of acids and bases.

How accurate is blood oxygen on an Apple Watch? ›

"The blood oxygen feature is fairly accurate, from the research I've seen, but it's not medical grade, so I would say overall, no, it's not very useful," Graham Bower, developer of iOS health app Reps and Sets and Apple Watch expert, told Lifewire via email.

What smartwatch do cardiologists recommend? ›

Top 3 features of best smartwatches for heart patients
Best smartwatch for heart patientsDisplayRating
Apple Watch SE (2nd Gen) [GPS 40 mm]1.78 inches4.6
Fastrack Reflex Play Smart Watch1.3 inch AMOLED3.1
Apple Watch Series 91.7 inches4.5
beatXP Vega1.43 inch Round AMOLED3.9
6 more rows
Jun 26, 2024

Do doctors recommend smart watches? ›

The use of smartwatches has been found to be effective in diagnosing the symptoms of various diseases. In particular, smartwatches have shown promise in detecting heart diseases, movement disorders, and even early signs of COVID-19.

Is it healthy to wear a smart watch all the time? ›

Radiation: Smartwatches use Bluetooth and Wi-Fi, which emit radiofrequency radiation. However, this radiation is non-ionizing, meaning it carries less energy than ultraviolet or X-rays and is unlikely to cause harm according to current research.

How accurate is blood oxygen on a smartwatch? ›

The overall accuracy was 84.9% for the Apple Watch and 78.5% for the Withings ScanWatch. The Spearman rank correlation coefficients reported a moderate correlation to ward-based photoplethysmography (Apple: rs=0.61; Withings: rs=0.51, both P<. 01).

Does a smartwatch show the correct oxygen level? ›

While a smartwatch or fitness band may do the same job as a pulse oximeter, users can often expect a difference in readings owing to variations in accuracy. This difference can arise from how the two devices actually measure your oxygen levels.

Which finger oximeter is most accurate? ›

When it comes to choosing the finger for pulse oximeter readings, the general consensus is that the middle finger or the index finger provides the most accurate results. These fingers are typically preferred due to their adequate blood flow and the thickness of the skin in the fingertip area.

How accurate are watch O2 sensors? ›

The Pearson correlation coefficient between watch and conventional oximeter measurements was 0.76. In four measurements (5%), the watch underestimated the true oxygen saturation by more than 5% spO2, and in one case by as much as 15%.

Why would my oxygen level be 92? ›

Low oxygen level, also called hypoxemia, is considered a reading between 90% and 92%. A reading this low means you might need supplemental oxygen or that there may be challenges that affect how your lungs function. A result below 90% indicates that you should seek medical attention.

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