Can Your Smartwatch Actually Monitor Vital Health Data—or Just Count Your Steps?

Reference photo: Pexels
In an era where technology is quite literally at our fingertips—or in this case on our wrist—smartwatches have become every day health companions for millions of individuals. By 2026, it is estimated that more than 100 million Americans will be using a smart watch. Along with there being additional technology we can use, these watches are hugely marketed as fitness trackers and wellness tools. These sleek devices promise to monitor everything from your daily steps to your heart rate, sleep patterns, and even blood oxygen saturation. But as wearable technology becomes more advanced and expensive, a critical question arises: Are these watches truly capable of tracking vital health data, or are they just popular pedometers?

Consumers are increasingly relying on these smartwatches not only to meet fitness goals but also to gain insight into their overall health. Smartwatches are poised to significantly reshape the healthcare landscape, with research predicting that wearable technology could lead to global cost savings of around $200 billion. A key development in this area is the integration of smartwatch data into electronic health records (EHRs), which is increasingly being adopted to improve patient tracking and support more tailored healthcare services. This can allow providers to use the time they would be using to collecting vital signs to instead spend more time completing other important areas during their patient’s appointment. It is to be noted that to retrieve the data one’s watch is collecting, the person much also have a smart phone and connect via Bluetooth.
Let’s dive into some health that can be tracked by the watch, that isn’t your typical 10,000 steps a day.
How Smartwatches Work
Modern smartwatches use photoplethysmography (PPG) to measure pulse and blood oxygen levels. This technique involves a light source and a photodetector that track variations in light absorption on the skin’s surface, reflecting changes in blood volume throughout the cardiac cycle. In practical use, PPG signals consist of two components: a quasi-static direct current (DC) element, which reflects light interactions with static tissues such as skin, venous blood, and non-pulsatile arterial blood; and a pulsatile alternating current (AC) component, which corresponds to dynamic changes in arterial blood volume with each heartbeat. By capturing thousands of readings per second, smartwatches can analyze these fluctuations to estimate heart rate, blood flow, and oxygen saturation levels. This high-frequency sampling allows for ongoing, non-invasive checking of heart activity, helping to spot problems early and improve health monitoring.

Reference photo: Unsplash
Heart Rate
Samsung Galaxy, Fitbit Sense, and Apple Watch are among the few smartwatches that are approved by the US Food and Drug Administration to detect irregular heart rhythms for adults who have never had a history of atrial fibrillation or AF (irregular heart rhythm). This is very significant because over 400,000 hospitalizations in the United States are due to atrial fibrillation. Failure to detect and diagnose AF can lead to more complication or even potential cardiac events.
A recent study, “Accuracy of a Smartwatch-Derived ECG for Diagnosing Bradyarrhythmias, Tachyarrhythmias, and Cardiac Ischemia,” explored how well the Apple Watch’s one-lead ECG can detect abnormal heart rhythms. The results were promising: the smartwatch was generally accurate in identifying common rhythm disturbances like bradycardia, tachycardia, and atrial fibrillation. However, its accuracy dropped significantly when detecting more complex arrhythmias like atrial flutter and atrial tachycardia—correctly identifying them only about 25% of the time. This highlights both the potential and the current limitations of smartwatch-based ECGs; while they can be helpful tools for basic heart rhythm monitoring, they’re not yet reliable enough for diagnosing more subtle or complex cardiac conditions.
Initially, devices using PPG technology are legally required to include a statement that they are not intended to diagnose medical conditions. In 2022, recent modifications to that statement were made by the FDA enabling the addition of features such as an “atrial fibrillation history,” making it easier for users to track their heart rhythm over time and share that information with their healthcare providers.
If a person with no known history of heart issues receives this type of alert, they should reach out to their primary care physician to discuss what to do next. This may involve undergoing an in-office electrocardiogram (EKG) and potentially using continuous, medical-grade monitoring for further evaluation.
Blood Pressure
Typical blood pressure cuffs have vibration sensors in a pneumatic cuff to obstruct one’s artery before it detects a systolic and diastolic pressure. In cuffless blood pressure monitoring systems, users are initially required to calibrate the device—typically a smartwatch or smartphone—by pairing it with a traditional blood pressure cuff. Multiple blood pressure readings are taken and compared to the PPG-derived blood flow data. This calibration allows the device to estimate future blood pressure readings using only PPG signals, without needing the cuff again.
In one of the first head-to-head comparisons between a wearable watch and a traditional upper-arm ambulatory. researchers evaluated both in-office and out-of-office readings in 50 adults, who both had these devices on the same non-dominant arm.

Researchers found that the wearable devices provided readings that closely matched those of the standard monitor in both environments, suggesting its reliability for continuous blood pressure monitoring. The findings support the clinical potential of wearable technology as a practical and accurate tool for managing hypertension, especially in out-of-office contexts where traditional monitoring can be less convenient.
Oxygen Levels
Next, a recent systematic review assessed how accurately the Apple Watch Series 6 measures blood oxygen levels (SpO2 ) compared to standard medical devices. The findings showed for the most part, the watch provides reasonably reliable readings in healthy adults. However, some discrepancies were noted, especially in cases of low oxygen saturation or among individuals with certain skin tones.
While the Apple Watch isn’t a replacement for clinical pulse oximeters, it can serve as a helpful tool for general wellness monitoring—so long as users recognize its limitations and don’t treat it as a diagnostic device.
Concerns in Regard to Wearable Technology
While wearable technology offers exciting possibilities for health monitoring and early detection of medical issues. It raises several important concerns. There’s a risk of over-reliance on wearables, where users might prioritize device feedback over professional medical advice. Next, accessibility and health equity come into play, as these technologies may be financially out of reach for some populations, potentially widening health disparities. Moreover, many wearables are not FDA-approved medical devices and can produce false positives or miss significant health events, leading to unnecessary anxiety or a false sense of security. Lastly, ensuring that these devices are fully charged and not experiencing any malfunctions, ensure they are computing accurate data.
Conclusion
Smartwatches have evolved far beyond simple step counters like offering users a glimpse into their cardiovascular health, sleep habits, and even blood oxygen levels. With increasing FDA oversight and emerging studies supporting their potential, these devices are starting to find a place in preventive healthcare. However, while the technology is advancing quickly, it still has limitations. Smartwatches can support wellness and early detection, but they are not substitutes for professional medical evaluations. Users must understand that wearable data should not replace clinical advice. As these tools become more integrated into our healthcare systems, staying informed, cautious, and connected to medical professionals will be key to using them safely and effectively. If one starts to feel heart palpitation, chest pain, or other unusual symptoms suddenly, they should contact their physician even if their smart watch says otherwise. Always trust your intuition and seek the appropriate medical attention to prevent further complications.
Grace N., APPE Student
Caillol, T., Strik, M., Ramirez, F. D., Abu-Alrub, S., Marchand, H., Buliard, S., … & Bordachar, P. (2021). Accuracy of a smartwatch-derived ECG for diagnosing bradyarrhythmias, tachyarrhythmias, and cardiac ischemia. Circulation: Arrhythmia and Electrophysiology, 14(1), e009260. Accessed: June 9th, 2025
Canali, S., Schiaffonati, V., & Aliverti, A. (2022). Challenges and recommendations for wearable devices in digital health: Data quality, interoperability, health equity, fairness. PLOS Digital Health, 1(10), e0000104. Accessed: June 11th, 2025
Hudock, Nicholas L., et al. “Wearable health monitoring: wave of the future or waste of time?.” Global Cardiology Science & Practice 2024.3 (2024): e202421. Accessed: June 11th, 2025
Kario, K., Shimbo, D., Tomitani, N., Kanegae, H., Schwartz, J. E., & Williams, B. (2020). The first study comparing a wearable watch‐type blood pressure monitor with a conventional ambulatory blood pressure monitor on in‐office and out‐of‐office settings. The Journal of Clinical Hypertension, 22(2), 135-141. Accessed: June 9th, 2025
Köhler, Charlotte, et al. “The Value of Smartwatches in the Health Care Sector for Monitoring, Nudging, and Predicting: Viewpoint on 25 Years of Research.” Journal of Medical Internet Research 26 (2024): e58936. Accessed: June 9th, 2025
Should I use a smartwatch to track my health. A doctor explains. https://www.cnn.com/2024/07/26/health/smartwatch-health-tracking-wellness. Accessed June 9, 2025. Accessed: June 9th, 2025
Windisch, Paul, et al. “Accuracy of the apple watch oxygen saturation measurement in adults: a systematic review.” Cureus 15.2 (2023). Accessed: June 11th, 2025.
Can Your Smartwatch Actually Monitor Vital Health Data—or Just Count Your Steps? Read More »