Oxygen Saturation Level: What’s Normal and What You Need To Know

Oxygen is one of the essential building blocks of life. Without oxygen, the human body can’t function. Oxygen saturation levels are a way of measuring how much oxygen is in the bloodstream. While most healthy individuals don’t need to monitor their oxygen saturation level, people with certain health conditions or athletes looking for peak performance can benefit from tracking oxygen levels.

Here, we’ll show you everything you need to know about your oxygen saturation level. From what it is to what causes low levels and how to treat low oxygen, this guide aims to answer all your questions.

What Is Oxygen Saturation?

An oxygen saturation level, also known as O2 sat, is simply the measurement for the amount of oxygen in your bloodstream. All organs in the human body need oxygen to function.

Hemoglobin — also known as haemoglobin and by the initials Hb or Hgb — is a protein found in red blood cells. This protein carries oxygen to all of your organs. On its way, it picks up carbon dioxide, which it transports back to the lungs to help with respiration. Your oxygen saturation level is the amount of oxygen that can be found in your hemoglobin proteins.

Here’s how it works on a scientific level. Red blood cells are packed with hemoglobin molecules — up to 270 million in each blood cell to be exact. These molecules contain iron, which binds to oxygen and carbon dioxide molecules, allowing the red blood cells to transport these items to the tissues in the body. Under normal conditions, these blood cells and the oxygen they deliver help to maintain normal body functions. When levels are too low, you may experience headaches and shortness of breath. Chronically low levels can lead to heart and brain problems.

What Is a Normal Oxygen Saturation Level?

A woman in a hospital gown has her oxygen saturation level measured with a pulse oximeter

Your oxygen saturation levels are an indicator of your health. Low levels may indicate an underlying problem such as a respiratory disease or vitamin deficiency. In general, normal levels of oxygen saturation are between 75 and 100 millimeters of mercury (mm Hg). Numbers below 60 mm Hg are cause for concern and typically require supplemental oxygen to keep your organs functioning properly.

When using a pulse oximeter, healthy numbers fall in the 94% to 99% range. Anything lower than 90% indicates a problem with your blood oxygen levels. These numbers are just a guideline. Depending on your overall health profile, your normal may be different from someone else. Things like the quality of room air, air pollution, pre-existing health conditions, and altitude can all affect normal oxygen saturation levels.

What Causes Low Oxygen Saturation?

A man at high altitude uses supplemental oxygen to improve his oxygen saturation level

Oxygen saturation levels are affected by a variety of agents including the amount of oxygen in outside air and nutrient deficiencies. Some respiratory diseases and heart disease can cause low oxygen saturation as well.

Hypoxemia is the term used by medical professionals to describe low oxygen levels. This condition can cause severe complications, and the danger of severe problems increases as the numbers decrease. Here’s a quick breakdown of the main causes of low blood oxygen levels.

High Altitude

Oxygen availability, the amount of oxygen in the outside air, can affect pulse oximetry readings. As you gain altitude, the air becomes thinner and contains less oxygen because there’s less atmospheric pressure compared to lower elevations. At high altitudes, healthy individuals may have pulse oximeter readings of 90% or slightly lower.

If you live in the mountains or at high altitude, regular pulse oximeter readings at 90% don’t necessarily indicate a problem. On the other hand, if you visit a high altitude destination — think the Himalayas or Machu Pichu — when you’re accustomed to living at a much lower altitude, you may feel light-headed or dizzy. That’s because your body isn’t used to the decreased availability of oxygen in the air. All this is to say that low oxygen levels in the atmosphere can impact the blood oxygen levels in your body.

People who live at low elevations and visit high elevations can suffer from high altitude sickness, a condition where your body doesn’t get enough oxygen. This is a bigger problem for people who live at low altitudes than high because your body adjusts the levels of oxygen available in the atmosphere where you live.

When you go up in elevation, your body struggles to adapt to the decrease in oxygen. People who live at high elevations are already acclimated to the oxygen conditions, which is why they may not develop low oxygen levels as easily as people who live at low elevations.

Blood Disorders

Anemia and nutritional deficiencies can cause oxygen saturation levels to plummet. Anemia is a condition where the body doesn’t produce enough blood cells to transport oxygen to the body. There are several types of anemia including iron deficiency anemia, sickle cell anemia, and vitamin deficiency anemia. Sickle cell anemia is an inherited condition where your body does not produce enough red blood cells. This can lead to low oxygen saturation levels.

People who are deficient in iron and other vitamins may also have low blood oxygen levels. That’s because iron is what binds to oxygen and carbon dioxide in the bloodstream. Deficiencies in vitamins including vitamin B12, vitamin C, and folate can also cause anemia and low oxygen saturation. Other heart and circulatory problems, including congenital heart defects, may make it more difficult for the body to get the oxygen it needs.

Respiratory Disorders

People with respiratory disorders or a lung condition like chronic obstructive pulmonary disease (COPD), chronic bronchitis, asthma, and emphysema may have low blood oxygen levels.

Injuries like collapsed lungs can also make it difficult for red blood cells to transport enough oxygen to your organs and tissues. A pulmonary embolism, where a lung artery becomes blocked, can also cause low oxygen saturation levels. Lung diseases and smoking can also contribute to the problem.

Symptoms of Low Oxygen Levels

Low oxygen levels can cause a range of symptoms. In some individuals, these symptoms are mild and almost unnoticeable. In others, the symptoms can be debilitating. Severely low oxygen levels can cause serious complications so it’s important to monitor symptoms and seek medical assistance if your blood oxygen levels are lower than normal. Here are some of the most common symptoms associated with hypoxemia:

  • Dizziness and confusion
  • Light-headedness
  • Rapid heartbeat
  • Pounding headache
  • Difficulty breathing, including shortness of breath and wheezing
  • Chest pain
  • Fatigue
  • Cyanosis, a condition where the skin develops a bluish tinge

How To Measure Oxygen Saturation Levels

A nurse holds out a man's arm as he has his oxygen saturation level measured with a pulse oximeter

There are two main tools used to measure blood oxygen levels: pulse oximeters and blood tests. Blood tests measure the oxygen saturation in the arteries (SaO2) while the pulse ox test measures the amount of blood oxygen as a percentage of the maximum amount possible (SpO2). You can take a pulse oximeter test at a doctor’s office or use one at home. Only a qualified nurse or healthcare provider can take an arterial blood gas test . Here’s how both tests work.

Arterial Blood Gas (ABG) Test

The ABG test is a blood test that measures the amount of oxygen in your red blood cells. The device gives a reading of oxygen called SaO2. Doctors can also get readings known as PaO2 — partial pressure of oxygen — through blood analysis. A doctor takes a small needle and uses it to draw blood from an artery, not a vein. Arteries contain red blood cells that are rich in oxygen. Veins typically transport carbon dioxide back to the heart, so they don’t contain oxygen and can’t be used to measure oxygen saturation.

A doctor or nurse will typically take blood from the artery near your wrist or the femoral artery near your groin. This type of blood test can cause more pain than the usual finger prick. The experience can cause mild discomfort as arteries are deeper than veins and these areas, including the wrist and groin, tend to be more sensitive.

Although the ABG test may be uncomfortable, it is extremely accurate. The test can also measure the pH level of your blood and identify other blood gases and components in your red blood cells. This can help a doctor identify what may be causing low oxygen saturation levels.

If you smoke, use the pulse oximeter test below instead. Smoking increases the amount of carbon monoxide in your bloodstream, which can cause false readings when you use this type of blood test.

Pulse Oximeter

Oxygen saturation can also be measured using a pulse oximeter, commonly called a pulse ox. Readings from this type of test are measured as SpO2. You may not recognize the name, but you’re probably familiar with these little devices. A pulse oximeter is the little tool that doctors and nurses place on your finger, typically when they’re also checking your blood pressure. This device uses two different wavelengths of infrared light absorption to get a reading of your pulse rate and the amount of oxygen in your blood cells.

You can attach the pulse oximeter to fingertips, ear lobes, or toes to get a reading. The test has a margin of error of 2%, meaning it’s less accurate than the ABG test. Dark nail polish colors and temperature can affect the readings. Though it’s not as accurate as the ABG test, it is a great way to get a quick reading without any pain.

The devices are affordable and can be purchased for use at home if you’re trying to monitor your blood oxygen saturation levels regularly. Biostrap’s Biometric Set includes a wristband sensor with a built-in pulse oximeter to make tracking your oxygen levels easy.

Treatments for Low Oxygen Saturation Levels

The main treatment for low blood oxygen saturation levels is supplemental oxygen. This can be performed in a hospital, doctor’s office, or at home. In all cases, the supplemental oxygen must be prescribed by a doctor.

If you’re not getting enough oxygen, start by visiting your primary care doctor. If your symptoms are severe, head to the ER or a critical care department. Your doctor can get you on an oxygen therapy regimen and can help identify what’s causing the problem.

During the visit, tell the doctor about your symptoms, when you started experiencing them, and whether you’ve recently noticed other changes in your health. The doctor will take a blood sample and measure your heart rate to get a reading of the level of oxygen in your bloodstream.

Depending on your diagnosis, you may need to supplement with oxygen for a day or two, or you may need long-term oxygen therapy if you suffer from a chronic disease. The doctor may prescribe medications to improve blood flow or treat nutritional deficiencies. Each case is different so it’s important to talk with a doctor to develop the best treatment plan.

Stay on Top of Your Health

A smiling couple drinks water after a workout

Low oxygen saturation levels can be a sign of an underlying health condition. The problem may be caused by a chronic condition or by environmental factors including smoking and pollution. The best way to stay healthy is to monitor your well-being. The Biostrap App helps you monitor your health with clinical-quality biometrics, including heart rate variability, oxygen saturation, and respiratory rate.

Biostrap makes it easy for you to monitor your oxygen saturation levels right on your phone. The app offers a visual breakdown of your hourly oxygen saturation levels and makes it easy to see differences when you’re sleeping and when you’re awake. The app also uses powerful scientific metrics to help you track your activity level, respiratory rate, and health conditions, which can all affect your oxygen saturation levels.

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