Smartwatches today aren’t just about checking time or tracking steps. They promise to monitor heart rate, blood pressure (BP), and even oxygen saturation (SpO₂). But here’s the big question: are these readings accurate, and are they safe to rely on?
In this post, I’ll share my personal take, explain how these devices work, discuss their limitations, and help you decide if your smartwatch should be a “doctor on your wrist” or just a fitness buddy.
How Smartwatches Measure BP & O₂
Smartwatches use PPG (photoplethysmography) – a sensor that shines light into your skin and measures how blood vessels reflect it.
- For SpO₂ (oxygen levels): They analyze light absorption differences between oxygenated and deoxygenated blood.
- For BP (blood pressure): Some use algorithms, pulse wave analysis, or need calibration with a real BP monitor.
Important: Unlike hospital-grade equipment, these are consumer gadgets, so they provide approximations, not diagnoses.
Are the Results Accurate?
From my research and experience:
- Oxygen (SpO₂): Most smartwatches are fairly close to medical-grade pulse oximeters (within ±2–3%), especially in healthy individuals.
- Blood Pressure: This is trickier. Many brands require calibration with a cuff. Without it, results may be inconsistent.
Case Study Example:
A 2021 study published in Nature Digital Medicine compared smartwatch BP readings to hospital monitors. Results showed reasonable trends but not enough accuracy to replace medical devices.
Is It Safe to Use Smartwatches for BP & SpO₂?
Yes, they’re safe. Smartwatches are non-invasive and use harmless LED lights.
But the risk lies in misinterpretation:
- Relying on smartwatch BP for hypertension management is dangerous.
- Using SpO₂ readings for COVID or respiratory conditions without medical confirmation can mislead patients.
Think of them as early warning signals rather than final results.
Expert Opinions
Doctors often suggest:
- Use smartwatches for trend monitoring, not diagnosis.
- Always validate results with medical-grade devices.
- Treat smartwatch health data as supportive, not definitive.
Smart Companion, Not a Doctor
Smartwatches measuring BP and O₂ are safe to use and can give approximate results. They are fantastic tools for fitness enthusiasts and for keeping an eye on trends. But they are not a substitute for medical devices or professional advice.
Here's how users seem to rate each brand on accuracy based on Flipkart and Amazon reviews
| Brand | SpO₂ Accuracy | BP Accuracy | HR / Fitness |
|---|---|---|---|
| Fire-Boltt | ~3 / 5 | ~2.5 / 5 | ~3.5 / 5 |
| Boat | ~2.5 / 5 | ~2 / 5 | ~3 / 5 |
| Fastrack | ~2 / 5 | ~1.5 / 5 | ~2.5 / 5 |
| Fossil | ~3.5 / 5 | ~3 / 5 | ~4 / 5 |
