Oxygen Saturation

Oxygen saturation measures how much of the oxygen-carrying protein in your blood is actually loaded with oxygen. It’s a vital indicator of how well your body is getting the oxygen it needs to function properly, and monitoring it has become a standard part of medical care.

Table of contents

• What Is Oxygen Saturation?
• How Your Body Uses Oxygen
• Normal Oxygen Saturation Levels
• How Oxygen Saturation Is Measured
• What Low Oxygen Levels Mean
• Ways to Increase Blood Oxygen Levels
• Oxygen Therapy

What Is Oxygen Saturation?

Oxygen saturation is a measurement that shows what percentage of your blood’s hemoglobin (a protein in red blood cells) is carrying oxygen^[1]. Think of hemoglobin as tiny delivery trucks traveling through your bloodstream. Oxygen saturation tells you how many of these trucks are actually loaded with oxygen cargo versus how many are running empty.

At the molecular level, each hemoglobin molecule has four special binding sites that can attach to oxygen molecules. This means one hemoglobin molecule can carry up to four oxygen molecules at a time during its journey through your blood^[1].

Your body tightly regulates oxygen levels because every tissue and cell in your body needs a constant supply of oxygen to work properly. When you don’t have enough oxygen in your blood, your brain, heart, kidneys, and other organs can be damaged^[2].

How Your Body Uses Oxygen

Understanding how oxygen moves through your body helps explain why oxygen saturation matters. When you breathe in through your nose or mouth, air travels into your lungs. Inside your lungs are millions of tiny air sacs called alveoli, where oxygen passes from the air into your bloodstream^[2].

Once oxygen enters your blood, it attaches to hemoglobin in your red blood cells. These oxygen-loaded red blood cells then travel throughout your body, delivering oxygen to all your organs, tissues, and cells. Your cells use this oxygen to create energy from the food you eat^[3].

After your cells use the oxygen, they produce a waste product called carbon dioxide. This carbon dioxide also binds to your red blood cells, which carry it back to your lungs. When you breathe out, you release this carbon dioxide from your body^[2].

Because only about 2% of oxygen in your blood is dissolved directly in the liquid part of blood, nearly all oxygen depends on hemoglobin for transport. This is why measuring how saturated hemoglobin is with oxygen gives a good picture of your body’s oxygen level^[3].

Normal Oxygen Saturation Levels

For healthy adults, normal oxygen saturation ranges from 95% to 100%^[4]. Some sources cite a slightly broader normal range of 96% to 100%^[5]. When oxygen saturation falls below 90%, it is considered low and may require medical attention^[4].

A healthy level of oxygen in the arteries is about 75 to 100 millimeters of mercury (mm Hg). Any value under 60 mm Hg indicates hypoxemia, which means low oxygen in the blood^[4]. When oxygen saturation drops below 89%, or when the oxygen pressure in arteries falls below 60 mmHg, supplemental oxygen is typically needed^[8].

It’s important to know that some people may have slightly different normal ranges. People living at higher altitudes often have lower readings because there is less oxygen in the air at high elevations^[5]. People with certain chronic conditions, like chronic obstructive pulmonary disease (COPD), may have target ranges that are lower, often between 88% and 92%^[1].

How Oxygen Saturation Is Measured

There are two main ways to measure oxygen saturation: pulse oximetry and arterial blood gas testing.

Pulse oximetry is the most common method. A small device called a pulse oximeter clips onto your fingertip, toe, or earlobe^[1]. This device is painless and noninvasive. It shines two types of light (red light and infrared light) through your skin and measures how much light is absorbed by your blood^[3].

The device can determine your oxygen saturation because oxygenated hemoglobin and deoxygenated hemoglobin absorb light differently. Blood that is well-oxygenated absorbs more infrared light, while blood with less oxygen absorbs more red light^[3]. The reading from a pulse oximeter is called SpO2, which stands for peripheral oxygen saturation^[6].

Healthcare providers use pulse oximeters frequently in hospitals, and you can also buy one to use at home from pharmacies or online stores^[2]. Pulse oximetry has become a standard part of medical care and is often considered a “fifth vital sign” along with blood pressure, heart rate, breathing rate, and temperature^[1].

The second method is an arterial blood gas (ABG) test. This test involves drawing blood from an artery, usually in your wrist, using a needle and syringe. The blood sample is then analyzed to measure the exact levels of oxygen and carbon dioxide, as well as the pH balance in your blood^[2]. This test provides more detailed information than a pulse oximeter and is more accurate, but it is more invasive^[4].

Some factors can affect the accuracy of pulse oximeter readings. These include very cold hands, poor blood circulation to the extremities, conditions that reduce blood flow to fingers like Raynaud’s phenomenon, and dark nail polish or artificial nails^[5].

What Low Oxygen Levels Mean

Low blood oxygen levels, called hypoxemia, can be caused by many different conditions. Hypoxemia is not an illness itself, but rather a sign of a problem with your breathing or blood flow^[4].

Many heart and lung conditions can cause low oxygen levels, including^[8]:

• Asthma
• Chronic obstructive pulmonary disease (COPD)
• Emphysema
• Bronchitis
• Pneumonia
• Pulmonary fibrosis
• Heart failure
• Congestive heart failure
• Lung cancer
• Anemia
• Sleep apnea

Symptoms of low oxygen levels can include^[8]:

• Shortness of breath or difficulty breathing
• Rapid breathing
• Fast or pounding heartbeat
• Headache
• Confusion
• Coughing or wheezing
• Bluish color to skin, lips, fingernails (called cyanosis)
• Extreme fatigue

When oxygen levels in your blood are too low, it can lead to hypoxia, which means low oxygen in your body’s tissues. While hypoxemia refers specifically to low oxygen in the blood, hypoxia means your organs and tissues are not getting enough oxygen. These conditions often appear together, but not always^[8].

Low oxygen can be life-threatening because your body’s cells cannot “save up” or “catch up” on oxygen—they need a constant supply to function^[8]. If you experience symptoms of low oxygen, especially if you have an underlying health condition, you should contact your healthcare provider or go to the emergency room immediately^[8].

Ways to Increase Blood Oxygen Levels

There are several natural ways you may be able to increase your blood oxygen level, especially if your levels are only slightly low and you don’t have a severe medical condition.

Breathe fresh air: Something as simple as opening your windows or going outside for a walk can increase the amount of oxygen you breathe in, which can raise your overall blood oxygen level^[2].

Practice breathing exercises: Certain breathing techniques can help your lungs work more efficiently. Diaphragmatic breathing (also called belly breathing) and pursed-lip breathing are simple exercises that can help open your airways and increase the amount of oxygen in your body^[2].

Quit smoking: If you smoke, quitting can significantly improve your oxygen levels. Many people find that their circulation improves just two to three weeks after quitting, and within one to nine months, shortness of breath decreases and oxygen levels rise^[11].

Exercise regularly: Cardiovascular exercise increases your breathing rate, helping you absorb more oxygen. Stretching also helps by allowing your muscles to receive more blood, oxygen, and nutrients^[2].

Maintain a healthy weight: Excessive weight can strain your respiratory system and reduce lung capacity. Keeping a healthy weight can improve how well your lungs work and increase blood oxygen levels^[2].

Stay hydrated: Drinking plenty of water helps keep your lungs hydrated, making them more efficient at dispersing oxygen into your bloodstream. The recommended daily water intake is about 15.5 cups for men and 11.5 cups for women^[2].

Maintain good posture: Sitting or standing up straight can improve your oxygen levels. Research shows that the sitting upright position provides the best oxygenation. Lying down for long periods can put pressure on your lungs^[2].

It’s important to note that these natural methods may help if your oxygen levels are only slightly low. If you have a serious medical condition causing low oxygen levels, or if your levels are very low, you will need medical treatment^[2].

Oxygen Therapy

When natural methods aren’t enough, oxygen therapy (also called supplemental oxygen) may be necessary. Oxygen therapy provides your body with extra oxygen beyond what you breathe from the air^[10].

Healthcare providers prescribe oxygen therapy when oxygen levels drop below 88%^[10]. Many people with lung diseases or breathing problems eventually need oxygen therapy to reduce breathlessness and maintain healthy oxygen levels^[10].

Oxygen therapy can be used at home, in medical facilities, or even while traveling. Modern oxygen systems come in different sizes, including portable options that allow you to continue your daily activities^[10].

Types of oxygen systems include:

• Compressed gas systems: Large metal cylinders that store oxygen as a gas under pressure. These are often used at home but eventually run out and need replacement^[10].
• Oxygen concentrators: Machines that take oxygen from the air in the room and concentrate it for you to breathe. These can be used at home and don’t run out like compressed gas tanks^[10].
• Portable oxygen systems: Smaller, lightweight systems that you can carry with you when you go out^[10].

Oxygen is delivered through tubing to a nasal cannula (small prongs that fit just inside your nostrils) or through a mask that covers your nose and mouth^[10].

Using supplemental oxygen can greatly improve quality of life and allow people with lung disease to stay active and continue doing the things they enjoy. However, oxygen is considered a medication and requires a prescription from a doctor^[10].

Your healthcare provider will determine how much oxygen you need and when you should use it—whether continuously, during activity, while sleeping, or at certain times. They will monitor your oxygen levels regularly to make sure you are getting the right amount^[2].

The treatment for low oxygen levels focuses both on providing supplemental oxygen and on treating the underlying cause of the low oxygen^[4].