Sensors in today’s smartwatches can detect your heartbeat, track how you sleep and even monitor blood oxygen levels. If Apple gets its way, your watch will be able to track your blood sugar (and possibly send reports about it to your doctor).
If you’ve ever wondered, “Just how accurate are these smartwatch readings?” You’re far from alone, so I took a look. Smartwatches and fitness watches have some serious flaws you should know about.
Paging Dr. Watch
It turns out cramming a bunch of sensors into a tiny watch doesn’t create the most legit results — who knew? If you’re seeing spikes or drops in readings for sleep states or blood oxygen levels, don’t panic — it’s happening to everyone.
- Sensors have problems with skin tone: It’s gotten so bad users have filed a lawsuit against Apple because blood oxygen sensors don’t work correctly on dark skin. Yikes! However, research indicates this may be a problem with many blood-oxygen sensors.
- Watches don’t reach medical levels of accuracy: High-grade studies are limited, but this one done on Garmin fitness watches found that the watches could measure neither energy expenditure nor blood oxygen levels with enough accuracy to make medical decisions.
- Step counters and calorie trackers are easily fooled: Smartwatches like the Apple Watch 6 and Fitbit Sense stink at measuring calories burned and can struggle to define steps walked. And don’t get me started on how vague sleep tracking can be!
OK, so smartwatches are only helpful for very guessy guestimates. But what can we do to make them better?
Take your health in stride
Here are a few figurative steps I think all smartwatch users should take while getting in their literal steps (plus a free play on words!).
- Size your watch for your wrist: Many accuracy problems are caused by loose-fitting watches that slip around on your arm. Buy one you can adjust.
- Focus more on heart rate than steps or calories. Your pulse is right there, so it’s no surprise watches are more accurate about heart rate than almost anything else.
- Don’t get stressed out over readings: Ironically, that stress will increase your heart rate and other vitals. Even worrying about sleep tracking can cause inadequate sleep (doctors call it orthosomnia). Don’t think of readings as hard numbers but rather general brushstrokes about your health picture.
- Watch readings over time instead of individual numbers: Those charts and graphs are more helpful than going number by number.
- Visit a doctor if you’re worried: Don’t waste time or energy obsessing over what your watch tells you. If you’ve got a serious concern, make an appointment like a grown-up.
My smartwatch picks
If you don’t have a smartwatch yet, here are a few good ones:
🤣 Having a smartwatch is great. On the one hand, you have something you can use to answer texts and stuff; on the other hand, you don’t. (Was that a groan I heard?)
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FAQs
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).
How accurate are smart watch health 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.
How accurate is smart watch blood glucose? ›
Smartwatches and rings that claim to monitor blood sugar have been shown to be inaccurate—setting you up for the potential consequences of inaccurate readings. In other words, the most accurate way to measure the amount of glucose hanging out in the blood is to go directly to the source—your blood.
How accurate are smart watches for steps? ›
Many devices do decently well tracking brisk walks. Like, if you took 1,000 steps on a treadmill going a few miles an hour, most trackers would be pretty accurate. The average tracker only undercounts steps during a brisk walk by about 2 percent.
What is a dangerously low oxygen level? ›
People should contact a health care provider if their oxygen saturation readings drop below 92%, as it may be a sign of hypoxia, a condition in which not enough oxygen reaches the body's tissues. If blood oxygen saturation levels fall to 88% or lower, seek immediate medical attention, says Dr. Lutchmansingh.
Which is more accurate, a smart watch or an oximeter? ›
In terms of accuracy, a wearable pulse oximeter is undoubtedly better than a smartwatch. In contrast, only the wearable pulse oximeter can achieve medical level use. Apple itself has emphasized that the sensors used in the Apple watch are not medical grade. The grades are for reference and guidance.
Is it healthy to wear a smart watch all the time? ›
It is not dangerous to wear a smartwatch at all times. Despite speculations of increased radiation damage because of the device being so close to your skin, the radiation emitted by smartwatches aren't as strong as the ones coming from your smartphone to cause any harm.
Which smart watch is the most accurate? ›
The best watch overall
The Apple Watch Ultra 2 is a dream smartwatch: next-level GPS accuracy, a sumptuous screen, gesture controls (you don't even have to touch it to operate the watch!), and all the usual stuff like taking and receiving calls on-wrist. Purely on specs alone, we rate it our top smartwatch.
What is the most accurate wearable device? ›
Fitbit was by far the most studied brand. In laboratory-based settings, Fitbit, Apple Watch, and Samsung appeared to measure steps accurately. Heart rate measurement was more variable, with Apple Watch and Garmin being the most accurate and Fitbit tending toward underestimation.
What is the FDA warning about smart watches? ›
The U.S. Food and Drug Administration (FDA) is warning consumers, patients, caregivers, and health care providers of risks related to using smartwatches or smart rings that claim to measure blood glucose levels (blood sugar) without piercing the skin.
They can be fairly accurate — a 2023 study found that a Samsung Galaxy watch provided readings close to results the users obtained at a doctor's office.
Can smartwatch detect diabetes? ›
Smartwatches and smart rings that market themselves claiming a non-invasive way to measure blood glucose have not been proven to be accurate, according to FDA's recent safety communication, which highlighted that use of these devices for glucose monitoring purposes on diabetes patients could result in inaccurate ...
Why is my smartwatch not accurate? ›
Check Watch Fit
Wearing the watch correctly can help with step accuracy. The watch should be snug above your wrist bone, but not too tight. It is properly tight when you can move the watch and the skin underneath moves with it as shown below.
Why is my smart watch not counting steps correctly? ›
If the step and heart rate tracking features are not working properly on your watch, the watch band or strap may be too loose or the watch's software might need updating. However, a simple reboot may solve the problem.
What is the most accurate watch for step counting? ›
The best pedometer watch depends on what additional features you might want. For pure step counting, the Fitbit Charge 5 is highly recommended for its accuracy and simplicity. For a more feature-rich experience, the Apple Watch Series 8 and Garmin Venu 3 are excellent choices.
How accurate are wrist oxygen monitors? ›
Pulse oximeters are most accurate when blood oxygen saturation is between 90% and 100%. Accuracy decreases when blood oxygen saturation is between 80% and 90%, and the devices are least accurate when saturation is below 80%. Keep in mind that readings may be off by a few percentage points.
What is a normal SpO2 level? ›
For most people, a normal pulse oximeter reading for your oxygen saturation level is between 95% and 100%.
How does your watch know your 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, ...
