How Smartwatches Detect SpO2 (Blood Oxygen Level) Detection

Blood oxygen saturation is probably one of the most important health topics after we all came to know Covid-19. To check the SpO2 level we can use the 2 most useful and handy devices: Oximeter, And SpO2 Monitoring smartwatch.

Today, we are going to know about how smartwatches detect Spo2.

In simple words, Using Bio-metric sensor smartwatches send LEDs inside the Blood where blood reflects and absorbs LEDs rays. Comparison of absorbed and reflected rays determines the Oxygenated and Deoxygenated Hemoglobin ratio, called SpO2.

Let’s talk dive deeper.

What Are The Key Method To Detect SpO2?

Before jumping into the process, you should know something about SpO2. Let’s start with the first question-

What Does It Mean By SpO2?

The Word SpO2 stands for Peripheral Capillary Oxygen Saturation. From the full form of SpO2, we understand that it refers to a connection of available Oxygen in blood.

In the definition of SpO2 or Oxygen saturation level, we can see a relation.

It says SpO2 refers to the amount of oxygenated hemoglobin as compared to the total amount of hemoglobin in the blood. To measure it users can use Pulse Oximeter and Smartwatches.

There are 2 main ways to measure Oxygen Saturation levels in the blood-

  1. Invasive way to measure the blood oxygen level
  2. Non-Invasive way to measure the blood oxygen level
What Spo2 Actually Tells About You?

The reading of an oximeter shows the SpO2 level that says the Oxygen saturation level in Blood. It is the comparison of Oxygenated Hemoglobin and Deoxygenated Hemoglobin.

Note: Oxygenated Hemoglobin means Hemoglobin(Red Blood Cells) that carries Oxygen in Blood.

Invasive Way To Measure Blood Oxygen Level

In this method, several medical equipment is required. Invasive methods include generally punching or cutting the skin by inserting medical instruments into the body.

Therefore, Invasive Blood Oxygen Saturation Level detection involves giving a few Milli-liters of blood to the Lab to test it medically. That is called Blood Gas Testing.

Difference Between invasive Oximetry Vs Non-Invasive Oximetry

Non-Invasive Way To Measure Blood Oxygen Level

Using a Non-Invasive way to measure Blood Oxygen level refers to using Pulse Oximeter or Smartwatches with Oxygen Saturation Level tracking.

Here, you don’t need to cut your skin to insert sharp medical instruments.

Like the Invasive way, the Non-invasive way of tracking oxygen saturation levels is sub-divided into 2 methods.

  1. Transmitting Oximetry (In Oximeters)
  2. Reflectance Oximetry (In Smartwatches)

Transmitting Oximetry (In Oximeters)

The process of measuring Spo2 in oximeters is called Transmitting Oximetry. In the following passages, we have shared the step-by-step process to track Oxygen Saturation levels-

In the Pulse Oximetry test, users used to place their finger or ear lobe in a clip-like digital tracking device (probe) The probe uses lights to measure oxygenated hemoglobin in the blood.

Mechanism Of Blood Oxygen Level Measurement In Oximeter

See how Oximeter technically measures Blood Oxygen Level-

Before Jumping into the steps, let’s take a look at the basic components of Oximeters. An oximeter mainly consists of Light Emitting Diode(LED), Photodetector, and A Screen or Display.

  1. At first, users must place an effective thinner body part such as a finger inside the device
  2. The 2 LED emits: Red LED (wavelength- 660nm) and; Infrared Ray (wavelength- 940nm) that passes through the finger
  3. On the other end, Photodetector receives the lights
  4. Oxygenated Blood absorbs more Infrared rays and allows Red rays
  5. On the contrary, Deoxygenated blood absorbs more Red Lights and Allow Infrared Rays
  6. From the readings, An Oximeter calculates the Spo2 Level
  7. Users can see the final result on the digital screen (In Percentage:%)

Now, in smartwatches or fitness trackers the oxygen tracking process is different. Let’s talk about the Reflection Oximetry that used to occur in smartwatches.

How To Check SpO2 In Smartwatch? (Reflectance Oximetry)

Smartwatches or fitness wearables give us the opportunity to measure SpO2 more comfortably. One of the biggest advantages of smartwatches is that biometric sensors are capable to measure SpO2 levels right on the wrist.

Users need not re-set the device in any kind of different position to measure the Oxygen levels.

how smartwatches detect SPo2

Here is the process of how Smartwatches measure Blood Oxygen levels:

  1. Behind the watch case, there are Bio-metric sensors
  2. Here you can see the LED array: LED and Detector
  3. LED lights pass through the skin and are reflected on the same side
  4. The detector receives the reflected lights from the same side
  5. After calculation, the algorithm shows the results on the Watch Screen

Why SpO2 is Important

We all know that oxygens are important to surviving. Without oxygen, you can stay alive for hardly a few minutes.

According to Home Care Mag, oxygen levels are important to maintaining all tissues in the human body. At low oxygen saturation levels, the tissue of your heart, brain, and lungs is used to get damaged.

In low oxygen, there is a special type of disease called Hypoxia that may happen. To avoid any severe tissue, users must check their Blood Oxygen Level after 2-3 hours.

By staying up to date about your health condition, you can necessary steps for your health.

If you are getting sudden up to 97 and then down 88 or slightly low you must care about it. Now, the oxygen level goes up and down.

However, Users should visit a medical center to consult with a doctor if she or he gets chest pain, rapid heartbeat, serious shortness of breath, or so on.

The best solution is to keep a Pulse OX or SpO2 tracking smartwatch and stay up-to-date about the oxygen level of your body.

Related: Are SpO2, SaO2, VO2 Max, and Fio2 The Same?

Are Smartwatches With SpO2 Accurate?

As mentioned earlier, there are 2 main ways to measure Blood Oxygen levels in our body.

Technically, smartwatches use Reflecting Oximetery but Transmitting Oximetry(Oximeter) is considered one of the most accurate non-invasive ways to detect blood Oxygen Levels.

High-quality smartwatches like Apple Watch Series 6 provides accurate result.

There is nothing like a 100% accurate result. Every device has its own fault. We can use smartwatches or health trackers to measure blood Oxygen Levels or SpO2. It will give you an instant update about your health.

For serious health issues, users must visit a clinic and run Invasive Blood Oxygen Level detection.

Why does the Spo2 level Fluctuate

The blood oxygen levels can fluctuate due to shortness of breathing. Health problems like sleep disease(Apnea), lung disease(Asthma, Bronkitese, Silicosis), and Covid-19, HGH altitude location is one of the causes of SpO2 fluctuation.

What Is The Ideal Level Of SpO2?

Oxygen level varies in different human bodies. The readings count from 0 to 100. It means no one should have a 100% SpO2 reading.

Anything below 94%-93% would be a matter of concern.

According to, the normal Oxygen saturation level in blood should be 95% or higher. People with Sleep Apnea, and Lung Disease could have 90% Oxygen levels.

When the oxygen level decreases to the recommended level, he or she must be given external oxygen.

Can Spo2 Be Above 100?

No. If the Oximeter or health tracker is showing more than 100 SpO2 you should calibrate it before use.

Can Spo2 Decrease Due To Anxiety?

Problems like anxiety, depression, and stress can interrupt the respiratory rate (Inhaling or exhaling Air) therefore the Oxygen Level may decrease naturally in the Blood. Psychological problems decrease oxygen in the blood which harms tissues and health internally.

Are Spo2 Level Lower In The Morning?

Oxygen level could be slightly lower than normal(96%) in the morning. Wrong sleep position, or sleep disease like Sleep Apnea shows lower than normal SpO2 (below 92%) after waking up.

Are Oximeters Reliable?

Oximeter or Pulse OX is a useful device to detect Blood Oxygen Levels. Unlike Invasive Blood Oxygen level detection, Oximeter provides an non-invasive method to measure SpO2 that requires a finger to detect run the test.

Using Transmitting Oximetry and Pulse OX measure the percentage of oxygenated hemoglobin. Unlike Reflactance Oximetery, Transmitting Oximetry is considered more accurate. That’s doctor recommended An Oximeter to measure SpO2 at home.

Here is a comparison between Transmittance and Reflectance Oximetry.

Which One Measures Accurate SpO2 Between Oximeter Vs Smartwatch

As mentioned earlier, Smartwatches use Reflectance Oximetry which is experimentally a little bit less accurate than Transmission Oximetry in Oximeters. Doctors and Physicians recommend oximeters to take serious checkups and smartwatches for regular updates.

Smartwatch is a handy option to measure crucial health factors like blood pressure, Heart rate, Pulse, Sleep quality, and so on. Using Bio-metric trackers smartwatches measure our internal health changes. However, smartwatch sensors are not as accurate as medical instruments till now.

Brands like Apple and Samsung are trying to improve the tracking accuracy of fitness trackers and they are nearly accurate to devices like Oximeters. But one should not use a smartwatch for clinical severe measurements.

Process Of Increasing Oxygen Level In Blood

Blood Oxygen Level increase is not a complex process. Anyone can follow some basic steps to increase blood oxygen level at home. Now, there are various medical supplements like CoQ10 (referred by Restoreactivemedicine.Org).

Although no medicines are totally side effects free still we have to use them. If the patient is suffering from Hypoxemia or Hypoxia then doctors will surely provide external Oxygen support or medicines.

However, we prefer to suggest natural ways to increase SpO2. You can follow several crucial exercises or Foods to increase the oxygenated hemoglobin in the Blood. These methods are helpful when you want to maintain the balance of oxygen levels in your day-to-day lifestyle.

Exercise To Increase Blood Oxygen Level

To increase the Blood oxygen level in the blood, people can have some breathing exercises like-

  • Quick smoking as a practice
  • Diaphragm/Belly breathing
  • Comfort sleep position to allow more oxygen

Foods To Increase Blood Oxygen Level

As we mentioned earlier, the best and bad side effectless way to increase Oxygen saturation level is natural super food. Here is a list of food that you can add in your diet. It will increase the level of O2 in blood.

  • Nuts
  • Grapes
  • Beetroots
  • Omega-3 fatty acids
  • Spinach
  • Lemons

To know more about How to increase Blood Oxygen saturation you can check this detailed post.

Related: Blood Pressure Monitoring Smartwatches

Best Smartwatches To Measure Blood Oxygen Level SpO2

Amazfit BipU Pro

When it comes quality Fitness tracking watches, Amazfit stands out in the Top 5. To monitor GPS, Sleep tracking, Hear rate to 20+ different sports modes Amazfit Bip U pro works super well on your wrist.

This is mid-range fitness and health tracking device that fits on your wrist.

Needless to mention, the smartwatch offers smart notifications signals such as incoming calls, text message, social media Apps, calender, Alarm clock, weather forecast, support control and so on.

Light wrighted 5 ATM water resistant device with 9 days battery life will not disappoint you. Moreover, users can operate built-in Alexa. Get deep health monitoring like stress level, sleep quality, female menstrual system, heart rate tracking, and so on.

Amazfit BipU Pro for Oxygen saturation tracking


  • Built-In GPS
  • Blood Oxygen Saturation Level
  • Good Battery Life
  • Light Weighted

Apple Watch Series 7

We have seen the Apple watch series from Apple Watch SE to Apple Watch Series 6. But Apple Series 7 is a real champ in terms of health and fitness tracking. Let’s first start with the display and outlook. Watch Series 7 is highly customizable straps, and watch faces.

The rectangular is sports-friendly to play games inside or outside of the home. Durability, flexibility, and Long battery life attracts users to make a decision to have this on their wrist. This device offers multiple crucial health factors such as ECG(Electro Cardiogram).

Moreover, it has smart notification with a smartphone, Built-in GPS, SpO2 Heart rate monitoring, sleep tracking and so on.

Spo2 monitoring smartwatch


  • ECG App and SpO2 Monitoring
  • Crack Resistibilility
  • Durability

Let’s wrapping up. The process of detection oxygen saturation is below:

Smartwatch use Bio-metric sensors that uses Transmission Oximetery to measure Blood Oxygen Level(SpO2). Using LED reflection and absorption sensor determines the amount of Oxygen in blood. The result is shown in the display in percentage.

It is a process that tells us how frequently the level SpO2 is fluctuating. No serious medical Blood Oxygen Saturation should be done in health tracking watch.

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