Measuring blood oxygen levels on Xiaomi Mi Band 5: A complete guide with tips for accuracy

Why measure saturation on a smart bracelet?

Fitness bracelet Xiaomi Mi Band 5 became one of the first budget wearable devices with the function of measuring blood oxygen saturation (SpO₂). This option, previously only available in professional pulse oximeters, now helps users track their health directly from their wrists, but how the sensor works, how accurate its readings are, and how to measure correctly are questions that many owners worry about.

In this article, we'll go through all the steps of measuring saturation on the Mi Band 5, from device preparation to interpretation of the results, learn what factors affect the accuracy of the data, how to distinguish normal from alarming, and why the bracelet sometimes gives an error, and also learn unique tips for calibrating the sensor, which are not in the official instructions.

Technical capabilities of the sensor SpO₂ Mi Band 5

The basis of the measurement of saturation on Xiaomi Mi Band 5 is the technology of photoplethysmography (PPG). The sensor emits two-length light waves (usually red and infrared spectra) that penetrate the wrist tissue and bounce off the blood. By analyzing how much light has been absorbed by hemoglobin, the algorithm calculates the percentage of oxygen saturation.

It is important to understand the limitations of the method:

• 🔴 Accuracy: the error can reach ±2% compared to medical pulse oximeters, due to lower sensor power and processing algorithms.
• 🔴 Depth of penetration: Light waves analyze blood in the capillaries of the skin, not in the arteries (as in hospital devices).
• 🔴 External factors: arm movement, bright light or loose bracelet fit distort the results.

For comparison, the table below shows the specifications of the Mi Band 5 sensor and the medical pulse oximeter:

⚠️ Warning: If your scores are consistently below 90% for no apparent reason (e.g., after intense exercise), don’t rely on the bracelet alone. See your doctor for medical equipment checks – this may be a symptom of hypoxia or lung disease.

Step-by-step: how to measure oxygen levels

Before the first measurement, make sure that your bracelet has the latest firmware version installed.

1. Open the Mi Fit or Zepp Life app on your smartphone.
2. Go to Profile. → Xiaomi Mi Band 5 → Firmware update.
3. If a new version is available, install it.

Now let's start measuring:

1. Activate the function: On the bracelet screen, swipe up to open the menu. SpO₂ (Stylized heart with wave and tap on it.
2. Wait 30 to 60 seconds: The screen will display pulse animation and the words Measurement... At this time, don’t move your hand or talk.
3. View the result: Once completed, the display display will display a percentage of saturation (e.g. 98%). To see the history of measurements, sync the data with the Mi Fit application.

If the bracelet gives an error You can not measure, check:

• 🔋 Battery level (must be above 20%).
• 💡 Lighting – too bright or flickering light interferes with the sensor.
• 🖐️ Density of fit – there should be no gaps between the skin and the sensor.

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For more accurate results, take measurements on the same hand (usually on the non-working hand – left for right-handed people) and at the same time of day, which will help to track the dynamics without the influence of external factors.

Decoding indicators: what do the numbers on the screen mean

Normal values of saturation for a healthy person:

• 🟢 95-100% is the optimal level. Oxygen in the blood is enough for all organs.
• 🟡 91-94% - mild decrease, can be observed in smokers, after intense training or at high altitudes (for example, in mountains).
• 🔴 ≤90% critically low (hypoxemia) requires immediate medical advice, especially if accompanied by shortness of breath or dizziness.

But context is as important as numbers.

• 🏃‍♂️ After running or strength training, saturation may drop temporarily to 92-94%, which is normal if it recovers in 5-10 minutes.
• 🛌 In sleep, the indicators often fluctuate between 93-97% due to changes in breathing.
• 🚬 In smokers, chronic saturation 92-95% is a sign of lung damage.

In the Mi Fit app, the data is displayed as a time-stamped graph.

• 📉 Sharp falls (e.g. 98% to 88% per hour) – may indicate sleep apnea or heart rhythm problems.
• 🔄 Cyclical fluctuations (saw chart) – often associated with unstable sleep or external stimuli (such as snoring).

⚠️ Warning: If the bracelet is saturating above 100%, it's a sensor error, not a "superhealth." Reboot the device and repeat the measurement.

Frequent Mistakes and How to Avoid Them

Many users receive inaccurate or conflicting data due to misuse of the wristband.

1. Too tight or too loose: If the bracelet clamps your arm, if the blood flow is disturbed, the sensor picks up the distorted data. If it dangles, the light waves scatter. Optimally, a finger should pass between the strap and the skin, but the bracelet should not move when the arm is shaken.
2. Measurement immediately after movement: After walking, climbing stairs or even vigorous gestures, blood flow in the capillaries of the wrist increases, which distorts the results. Wait at least 5 minutes at rest.
3. Ignoring external factors: Bright sun, fluorescent lights, or even wrist tattoos interfere with the sensor, take measurements in the shade or in room light.
4. Dirty or sweat sensor: Sweat, cream or dust on the sensor scatter light.Rub the bottom of the bracelet with a soft dry cloth before each use.

Another common problem is that the bracelet does not see the pulse before the measurement. SpO₂. This happens if:

• 🩹 There is a scar or scar on the wrist (broken blood flow).
• ❄️ Skin too cold (vessels are narrowed) Massage your hand or warm it.
• 🧴 You have used a cream with reflective particles (for example, with a SPF-protection).

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For maximum accuracy, take 3 measurements in a row at 1 minute intervals and take the average. This will help to eliminate random errors.

Comparison with other devices: how accurate is the Mi Band 5

To assess the reliability of the Xiaomi Mi Band 5 data, we conducted a test: at the same time we measured saturation on the bracelet, Beurer medical pulse oximeter. PO 30 and Apple Watch Series 6. Results (average for 5 measurements):

Conclusions:

• 📊 Mi Band 5 lowers the performance by 1-2% compared to a medical device, but remains within the stated margin of error (±2%).
• ⏱️ Measurement time is 3-5 times longer than that of professional devices.
• 🔄 The range of values is wider - this means that for reliability it is necessary to carry out several measurements in a row.

For reference: in the budget segment, the Mi Band 5 shows better accuracy than counterparts from the Huawei Band 4 or Honor Band 5, where the error reaches the margin of error. ±However, it is inferior to flagship smartwatches (for example, Garmin Venu 2 or Samsung Galaxy Watch 4), which use more advanced sensors.

Additional functions: sleep monitoring and notifications

In addition to manual measurements, the Mi Band 5 can automatically track saturation during sleep.

1. In the Mi Fit app, go to Profile → Xiaomi Mi Band 5 → Sleep monitoring.
2. Activate the Measurement option SpO₂ dreamily.
3. Select the frequency of measurements: Frequently (every 5 minutes) or Rarely (every 30 minutes).

In the morning, a schedule with:

• 📈 Oxygen levels by the clock.
• 🛌 Sleep phases (deep, light, REM).
• ❤️ Average pulse per night.

If sleep saturation regularly falls below 90%, it may indicate obstructive apnea syndrome (stopping breathing).

• 😴 Frequent awakenings.
• 💤 Loud snoring.
• 😓 Morning headaches.

⚠️ Attention: Automatic monitoring of saturation consumes a lot of battery. With frequent mode, the bracelet will discharge in 2-3 days instead of the usual 7-10.

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To extend the bracelet’s life, turn off automatic monitoring. SpO₂ It is enough to measure saturation 2-3 times a day manually: in the morning, in the afternoon and before going to bed.

FAQ: Answers to Frequent Questions