Smartwatches have come a long way since their early days, and one of the biggest areas of growth has been their use as at-home medical devices. Despite not being approved by the FDA as actual medical devices, many smartwatches now come with an oxygen sensor that can be used to measure blood oxygen saturation and VO2 max. This article will guide you through some of the best smartwatches with oxygen sensors out there today.
What is blood oxygen saturation?
Maintaining the right oxygen level is vital for the proper functioning of your internal organs. For example, people with a lung condition may have lower blood oxygen saturation than those whose lungs are healthy, so measuring this saturation can help them get the treatment they need.
Oxygen is carried around your body by your red blood cells and, specifically, by a molecule in your red blood cells called hemoglobin. Your blood oxygen saturation is a measure of the ratio of hemoglobin molecules that are currently carrying an oxygen molecule compared to the hemoglobin molecules that aren’t carrying anything. It is expressed as a percentage, and the healthy range is 95% – 100%.
Blood oxygen saturation is measured in a healthcare setting using a pulse oximeter. This is a sensor that is placed on the fingertip or earlobe. It works by shining light wavelengths through the skin to measure the blood oxygen level. For example, blood that contains the right amount of oxygen will absorb more infrared light (and let more red light pass), whereas blood that doesn’t contain enough oxygen will absorb more red light (and let infrared light pass). The blood oxygen sensor in the pulse oximeter can measure these differences in the light reflected and use that to calculate the blood oxygen saturation.
In smartwatches, blood oxygen saturation level is detected using an SPO2 sensor, and the read-out you get will give you your SPO2 level. This is the same thing as your blood oxygen level.
Understanding the differences between VO2 max and blood oxygen saturation
VO2 max and blood oxygen saturation are often confused, but they measure pretty different things that each have different implications for your health.
Whereas blood oxygen saturation can measure ongoing lung problems, VO2 max measures your overall fitness level.
To break it down a little, let’s look at what VO2 max means. The V = volume, O2 = oxygen, max = maximum. It measures the maximum amount of oxygen a person can utilize while exercising.
Technically speaking, the number you see will be how many millimeters of oxygen is used by each kilogram of the body weight. Therefore, it is expressed as the ml per kilo of body mass per min.
In terms of measuring VO2 max, it is obtained using a pulse oximeter in the same way as blood oxygen monitoring. Still, it doesn’t give you the percentage blood oxygen saturation level.
VO2 max is affected by age, gender, and body weight, so these aspects need to be considered. To calculate your VO2 max, your smartwatch will measure your pulse using the heart rate monitor and your pace while running and create an estimate of your VO2 max based on this. While this estimate doesn’t calculate the oxygen level directly, it is around 95% accurate compared to lab tests that use an oxygen-detecting mask and a treadmill.
Who can benefit from measuring blood oxygen saturation?
Your blood oxygen saturation level measures how well your lungs are functioning. People with chronic conditions that can affect their lungs capacity will benefit most from blood oxygen monitoring.
These conditions include emphysema, COPD, pneumonia, asthma, anemia, heart disease, and lung cancer.
However, even if you don’t have one of these conditions, you can still benefit from blood oxygen monitoring. It has become more popular in the era of Covid as it is a way of seeing how well your lungs are functioning with the virus, but it can also be used for other respiratory infections and sleep apnea.
Many smartwatches will include sleep tracking in their health monitoring. Sleep tracking will use a variety of measures, including skin temperature, movement sensors, and heart rate monitor, but for sleep apnea, the SPO2 monitor is essential.
When you have sleep apnea, you will stop breathing periodically throughout the night. Many people are unaware that they have the condition but will experience feeling fatigued even after a whole night’s sleep. An SPO2 monitor can pick up these periods of not breathing as they affect your blood oxygen saturation.
Of course, seeing these measurements on your smartwatch isn’t a diagnosis in and of itself, but they can spur you to see your healthcare provider for further testing.
And if you plan on climbing any mountains, your SPO2 levels will tell you how well your lungs are coping with the change in altitude.
Is a smart watch blood oxygen sensor accurate and reliable?
Your smartwatch’s blood oxygen sensor isn’t the same as a true pulse oximeter. So should you take its readings with a grain of salt?
There is some conflicting evidence in the literature about the accuracy and reliability of smartwatch SPO2 level measurements, and this has the Washington Post declaring them “mostly useless.” But the picture isn’t as straightforward as that.
One study looked at the accuracy of readings from the BodiMetrics Performance Monitor and the Everlast smartwatch. The researchers found that the heart rate monitoring met clinical accuracy guidelines, but the other measurements, including high blood pressure monitoring and SPO2 level monitoring, did not. They concluded that selling these at-home monitors without clinical validation was a “public health concern.”
There has been a range of conflicting studies, however, that go against this conclusion. One study compared pulse oximeter readings with Apple Watch Series 6 blood oxygen sensor in lung patients and found a strong positive correlation between the readings, which demonstrated that the Apple Watch Series 6 was a reliable way of measuring heart rate and SPO2 level.
Another study looking at Covid patients found that the Samsung SpO2 sensor had an accuracy within clinical FDA guidelines.
So what can we conclude from this? First, each of the studies used different smartwatches/smartphones, so maybe the differences in reliability can be ascribed to differences in the blood oxygen sensor reliability between them.
It is probably safe to assume that your SPO2 sensor tells you something that could be important. Still, it is always prudent to check in with your healthcare provider for a clinical pulse oximeter test to validate the results.
Best smartwatch with an oxygen sensor in 2022
Now we’ve looked into what blood oxygen saturation is and how accurate smartwatches are, let’s look at the best smartwatches you can find with this function this year.
Best overall: Apple Watch Series 7
- WHY APPLE WATCH SERIES 7 — The most advanced Apple Watch features powerful health innovations like...
- EASILY CUSTOMIZABLE — Available in a range of sizes and materials, with dozens of bands to choose...
- INCREDIBLE DURABILITY — Built to be tough. It’s more crack resistant, it’s dust resistant, and...
- STAY CONNECTED — Send a text, make a call, listen to music and podcasts, use Siri, or call for...
- MOST ADVANCED HEALTH FEATURES — Keep an eye on your blood oxygen with a revolutionary sensor and...
Apple has leaned into health monitoring with their most recent Apple Watch. So if you want the best smartwatch with the most health features, the Apple Watch Series 7 does have just about everything.
It features a blood oxygen sensor (SpO2) that will tell you your blood oxygen level. In the study that we looked at, the Apple Watch Series 6 was found to be highly accurate with this measure, so you can assume that the Series 7 also has an accurate SpO2 monitor.
It also features a heart rate monitor that will notify you if your heart rate gets too high or too low and if it detects an irregular heart rate (arrhythmia). In addition, it has sleep tracking and sleep health features, menstrual cycle tracking, fall detection features to notify people if it detects you are falling over, an ECG, and a range of mental health features.
All in all, the Apple Watch Series 7 has just about everything. The only feature it lacks, available on some smartwatches, is a blood pressure monitor. However, the practicalities of including a physical blood pressure monitor do mean that the strap’s physical design would have to change quite drastically, so this could be the reason. Either way, you won’t be able to look out for high blood pressure with the Apple Watch Series 7.
You can also expect a wide range of fitness features, including activity rings to get you moving, heart rate monitoring, and a wide range of workouts accessible via Apple Fitness Plus.
The Apple Watch Series 7 will sync perfectly with your iPhone, giving you access to phone calls, text messages, app notifications, and more.
- A near-complete range of health monitoring features, including blood oxygen saturation
- Clinically demonstrated accuracy of its sensors
- One of the only smartwatches with fall detection included
- More expensive than many other smartwatches
- No blood pressure monitor
- Low battery life
Best for Android users: Samsung Galaxy Watch 4
- BODY COMPOSITION ANALYSIS: Galaxy Watch4 is the first smartwatch to off body composition data right...
- BETTER SLEEP STARTS HERE: Wake up feeling refreshed and recharged with advanced sleep tracking; When...
- BE SMART ABOUT YOUR HEART: Take care of your heart with accurate ECG monitoring and keep an eye on...
- MAKE EVERY WORKOUT COUNT: Get the most out of every exercise session with advanced workout tracking...
- GO THE EXTRA MILE: Improve your runs with advanced running coaching technology; VO2 Max readings...
The Samsung Galaxy Watch 4 has also leaned into health monitoring in a big way, although they have taken a slightly different approach than Apple.
One of the studies we looked at examined a Samsung oxygen sensor (although not one in a smartwatch) which was demonstrated to be highly accurate, so there’s a good chance that the one in the Samsung Galaxy Watch 4 will be.
The Galaxy Watch 4 also features heart rate monitoring, an ECG, sleep tracking, and stress tracking alongside blood oxygen monitoring.
One of its stand-out health features is its body composition analysis. It uses a heart rate monitor, SPO2 monitor, and bioelectrical impendence analysis (BIA) to measure and track your body composition, giving you a lot of information about your health and fitness.
Controversially, the Galaxy Watch 4 does have blood pressure monitoring. However, it doesn’t use a blood pressure strap as dedicated blood pressure smartwatches do. Instead, it calculates an estimate of your blood pressure using light sensors and the time between your heart contracting and the pulse arriving at your wrist. Whether or not this method is accurate is still being debated (and it isn’t FDA-approved), but blood pressure monitoring is there.
The Galaxy Watch 4 also Galaxy has a range of fitness features, including workout-tracking, heart rate monitoring, activity tracking, and sharable leaderboards.
It will also sync with your Android smartphone to give you access to messages, phone calls, music, and more.
- Innovative health features such as stress tracking, body composition analysis, and blood pressure monitoring
- Accurate SPO2 sensor
- Slightly better battery life than the Apple Watch Series 7
- Body composition analysis and blood pressure monitoring may be too far ahead of their time and not accurate
- Battery life is still low compared to many other smartwatches
- Expensive compared to other smartwatches on the market
Best for runners: Garmin Forerunner 245 GPS Running
- GPS running smartwatch with advanced training features
- Evaluates your current training status to indicate if you’re undertraining or overdoing it; offers...
- Get free adaptive training plans from Garmin Coach, or create your own custom workouts on our Garmin...
- Provides advanced running dynamics, including ground contact time balance, stride length, vertical...
- Safety and tracking features include incident detection (during select activities) which sends your...
Garmin has always been the smartwatch of choice for many runners. And the Garmin Forerunner 245 is no exception. There is less of a focus on general health monitoring but a more in-depth examination into physiological measures that are important to the very fit.
It has a blood oxygen monitor for measuring your SPO2, although it is presented in terms of seeing how your body performs at high altitudes rather than monitoring your health. It also has stress monitoring, heart rate variability tracking,
You can see a measure of your VO2 max, how your workouts are affected by anaerobic/aerobic training, heat, and altitude. In addition, you can get a measure of your recommended recovery time based on a variety of physical measures, and you can see which heart rate zones you are in when you are training.
It can help you to achieve your fitness goals with downloadable training plans and other features such as rep counting. It also has stress monitoring, heart rate variability tracking, and a wide variety of running tracking tools.
- It has everything a runner or health enthusiast needs to track their health and fitness, with features not seen in many other smartwatches
- VO2 max monitoring
- A lower price point than Apple Watch and Samsung Galaxy Watch
- Fewer health monitoring features than many other smartwatches
- Of little use, if you don’t engage in exercise regularly
- Unclear how accurate the SPO2 monitor is
Best for health features: Fitbit Sense
- EDA Scan app detects electrodermal activity which may indicate your body's response to stress and a...
- Assess your heart for atrial fibrillation –a heart rhythm irregularity- and easily share results...
- An on-wrist skin temperature sensor tracks yours each night so you can see how it varies. You can...
- High & low heart rate notifications alert you if yours seems above or below your average.Battery...
The Fitbit Sense was designed with health monitoring in mind, and it has a wide range of features to reflect that. In addition, it brings together all of the different health features across the various Fitbit devices in one place.
It has an SPO2 sensor for measuring your blood oxygen saturation. On top of that, it has 24/7 heart rate monitoring with high and low heart rate alerts. The Fitbit Sense will also measure your breathing rate and heart rate variability (an important measure of your health and fitness). So, all in all, you can expect to have a comprehensive overview of the functioning of your respiratory and cardiovascular systems.
One of the big selling points of the Fitbit Sense is its EDA sensor. This measures changes in your skin conductance as a measure of stress, and the app will give you an overall stress score using this measure alongside other measures such as your heart rate and sleep score.
Its sleep tracking is one of the most comprehensive on the market right now. You will see a detailed breakdown of your sleep duration, sleep stages (light, deep, REM sleep), breathing rate, and heart rate. And you will see an overall sleep score for each day. It also features snore detection.
In terms of fitness, you will have the usual access to the Fitbit fitness features via Fitbit Premium. In addition, your Daily Readiness Score collates the data from your sleep, activity, and health to tell you how hard you should push yourself with exercise that day. And when you are working out, you can easily see which heart rate zones you are hitting.
With its 6-day battery life, this is a smartwatch that you can use to monitor your health with ease.
- Clear and comprehensive health monitoring at an affordable price
- 6-day battery life
- Innovative EDA stress moniroting features
- Need a subscription to Fitbit Premium to access many features
- No atrial fibrillation detection
Best for outdoors: Garmin Fenix 6
- Fit for performance with rugged, sophisticated design that features an always-on 1.3” (18% larger...
- Enhanced estimated wrist heart rate and Pulse Ox to support advanced sleep monitoring and altitude...
- Advanced training features include PacePro for grade-adjusted pace guidance throughout your activity...
- Navigate the outdoors with preloaded TOPO maps, ski maps for over 2,000 worldwide ski resorts,...
- Support for Garmin Pay contactless payments (not all countries and payment networks are eligible),...
This smartwatch is designed with intrepid explorers, with a truly impressive array of features. For example, its SpO2 monitor is focused on altitude acclimatization for when you are hiking up a mountain, and the other features are similarly specialized.
Its PacePro features help you stay on track with your pace along your route, and it has round-trip routing that will plan a route for you that takes you right back to your starting point.
One of the most valuable features for the outdoors-type is its topographical and ski maps, with the ski maps pre-loaded from thousands of resorts and golf courses. In addition, its ABC sensors take into account elevation, weather, and a 3-axis electronic compass to help you plan your route. And its multi-GNSS support means that you can access GPS data even in areas where standard GPS wouldn’t provide coverage.
There is also a hydration tracker, which is invaluable if you are hiking for long distances, and Climb Pro features to help you plan your rock climbing route.
Its battery life is 14 days as standard, but if you turn on expedition mode, which puts it into an ultra low-powered GPS, it means it can last for weeks.
- Second-to-none features for outdoor sports and activities
- Very good battery life, especially in expedition mode
- Very expensive compared to many other smartwatches
- Not of much use for people who don’t take part in outdoor activities
Best for continuous readings: Amazfit GTS 2
- INTELLIGENT VOICE ASSISTANCE: You can talk to Alexa on your Amazfit GTS 2e. Set alarms and timers,...
- EXTENDED BATTERY LIFE& GPS BUILT-IN: With deeply optimized system battery management, the smartwatch...
- 90 BUILT-IN SPORTS MODES & 5 ATM WATER-RESISTANCE: The sport fitness watch features 90 built-in...
- ALL-ROUND HEALTH TRACKING: Equipped with the latest self-developed BioTracker 2 PPG high-precision...
- WEAR YOUR STYLE ON YOUR WRIST: The 1.65-inch HD AMOLED screen is comparable in clarity to the latest...
The Amazfit GTS 2 describes itself as “style meets health,” and it does hit the perfect balance between the two. You can expect constant monitoring of your heart rate with notifications if it reaches abnormal levels.
With your heart rate data, you will get a PAI score. Rather than focusing on the number of steps you take per day to measure your activity levels, the Amazfit GTS 2 focuses on how often you have raised your heart rate. This is more in line with the guidance from organizations such as the World Health Organization, which recommends 150 minutes of exercise that raises your heart rate per week.
This health evaluation is customized for each user, depending on height, weight, age, and gender.
The Amazfit GTS 2 will also measure your blood oxygen levels and breathing rate and give you a detailed breakdown of your sleep quality, including sleep duration and cycles.
It measures stress levels, but it doesn’t use an EDA sensor, and it has enviable 7-day battery life.
- Continuous customizable health monitoring
- Heart rate-based activity tracking
- 7-day battery life
- No EDA sensor for the stress monitoring
- No ECG, blood pressure monitoring, and limited access to music streaming
Our favorite that isn’t a smartwatch: Fitbit Charge 5
- Optimize your workout routine with a Daily Readiness Score that reveals if you’re ready to...
- Get a daily Stress Management Score showing your body’s response to stress and take steps to...
- Track your heart health with high & low heart rate notifications and a compatible ECG app (The...
- With the Health Metrics dashboard, track SpO2, heart rate variability, skin temperature variation...
- See your real-time pace & distance without your phone using built-in GPS during outdoor activity,...
Not everyone wants a full smartwatch for their health monitoring. The Fitbit Charge 5 is a fitness tracker that strips away all of the potentially unnecessary extras that you would find in a smartwatch to focus solely on your health and fitness.
In fact, it is our favorite fitness tracker of the year. It has all of the health and fitness features of the Fitbit Sense, without the higher price tag and smartwatch extras.
If you have trouble accessing your SPO2 data on your Fitbit Charge 5, check out our handy troubleshooting guide.
To wrap up
Bloody oxygen (SPO2) monitoring used to be unusual in a smartwatch, but it is slowly becoming one of the standard features of the latest generation of smartwatches and fitness trackers. Of course, the best smartwatch for you will depend on how you want to use the watch, with some focused on general health monitoring but others focused on specific individual needs such as running or outdoor sports. Whichever you choose, SPO2 can be an important measure of your lung functioning, pick up on potential sleep apnea, and help you monitor how well your body is coping with changing altitudes. A helpful feature indeed!