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Low Blood Oxygen: Causes, Symptoms and Treatment

Low Blood Oxygen: Causes, Symptoms and Treatment

Apria Editorial |

If you have low blood oxygen levels, you may experience symptoms like shortness of breath, headache, confusion, and bluish skin. Low blood oxygen, also known as hypoxemia, is a serious condition that can affect your heart, brain, and other organs. In this article, we will explain what causes low blood oxygen, how it is diagnosed and treated, and how you can prevent it.

What is low blood oxygen?

Low blood oxygen is when the amount of oxygen in your blood measures less than normal. Oxygen is essential for your cells to function properly and produce energy for your body and brain. When you breathe in, air enters your lungs and reaches tiny air sacs called alveoli. The alveoli are surrounded by blood vessels called capillaries, where oxygen from the air passes into your blood and carbon dioxide from your blood passes into the air. This process is called gas exchange.

When gas exchange is impaired in some way, your blood may not get enough oxygen or may have too much carbon dioxide. This can lead to low blood oxygen levels or high carbon dioxide levels, or both. Low blood oxygen levels can also occur if you have a problem with your heart or blood vessels that reduces the amount of blood flow to your lungs or tissues.

Low oxygen levels in blood can be measured by a test called arterial blood gas (ABG), which involves taking a blood sample from an artery, usually in your wrist. The ABG test can also measure the amount of carbon dioxide and other gases in your blood, as well as the pH (acidity) of your blood. Normal values for oxygen in arterial blood are between 75 and 100 millimeters of mercury (mm Hg). If your oxygen level is below 75 mm Hg, you have hypoxemia.

Another way to measure your blood oxygen level is by using a pulse oximeter, which clips onto your finger and uses light to estimate the amount of oxygen in your blood. The pulse oximeter reports your oxygen saturation, which is the percentage of hemoglobin (the protein that carries oxygen on red blood cells) that is bound to oxygen. Normal values for oxygen saturation are between 95 and 100 percent. If your oxygen saturation is below 90 percent, you may have hypoxemia.

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What are the causes of low blood oxygen?

There are many possible causes of low blood oxygen, depending on whether the problem is with your lungs, heart, or blood vessels. Some common causes include:

  • Lung diseases, such as chronic obstructive pulmonary disease (COPD), asthma, pneumonia, bronchitis, pulmonary edema (fluid in the lungs), pulmonary embolism (blood clot in the lungs), lung cancer, or lung injury.
  • Heart diseases, such as congestive heart failure, coronary artery disease, heart attack, heart valve problems, or congenital heart defects.
  • Blood diseases, such as anemia (low red blood cell count), polycythemia (high red blood cell count), sickle cell disease, or hemoglobin disorders.
  • High altitude, where the air pressure and oxygen level are lower than at sea level.
  • Sleep apnea, where you stop breathing briefly during sleep.
  • Smoking, which damages your lungs and reduces their ability to transfer oxygen into your blood.
  • Carbon monoxide poisoning, which occurs when you inhale a colorless, odorless gas that binds to hemoglobin and prevents it from carrying oxygen.

What are the symptoms of low blood oxygen?

The symptoms of low blood oxygen may vary depending on the severity and duration of the condition, as well as the underlying cause. Some common symptoms include:

  • Shortness of breath or difficulty breathing
  • Rapid or irregular heartbeat
  • Chest pain or tightness
  • Headache or dizziness
  • Confusion or disorientation
  • Fatigue or weakness
  • Bluish color of the skin, lips, or nails (cyanosis)
  • Loss of consciousness or coma

How is low blood oxygen diagnosed?

If you have symptoms of low blood oxygen, you should seek medical attention as soon as possible. Your doctor will ask you about your medical history, perform a physical examination, and order some tests to confirm the diagnosis and identify the cause. Some tests that may be done include:

Arterial blood gas (ABG) test: As mentioned earlier, this test measures the amount of oxygen and carbon dioxide in a sample of arterial blood taken from your wrist or another artery. It also measures the pH (acidity) of your blood. This test can help determine how severe your hypoxemia is and whether you have respiratory acidosis (too much carbon dioxide) or respiratory alkalosis (too little carbon dioxide).

Pulse oximetry: This test uses a device that clips onto your finger and measures the amount of oxygen in your blood by using light. It reports your oxygen saturation, which is the percentage of hemoglobin that is bound to oxygen. This test is less invasive and more convenient than an ABG test, but it may not be as accurate or reliable, especially if you have poor circulation, cold fingers, nail polish, or artificial nails.

Chest X-ray: This test uses a small amount of radiation to create an image of your lungs and chest. It can help detect lung diseases or conditions that may cause low blood oxygen, such as pneumonia, pulmonary edema, pulmonary embolism, or lung cancer.

Electrocardiogram (ECG or EKG): This test records the electrical activity of your heart using electrodes attached to your chest, arms, and legs. It can help detect heart diseases or conditions that may cause low blood oxygen, such as congestive heart failure, coronary artery disease, heart attack, or heart rhythm problems.

Echocardiogram: This test uses sound waves to create an image of your heart and its valves. It can help measure the size, shape, and function of your heart and detect any abnormalities that may affect blood flow or oxygen delivery, such as heart valve problems or congenital heart defects.

Complete blood count (CBC): This test measures the number and types of cells in your blood, such as red blood cells, white blood cells, and platelets. It can help detect blood diseases or conditions that may cause low blood oxygen, such as anemia, polycythemia, sickle cell disease, or hemoglobin disorders.

How is low blood oxygen treated?

The treatment of low blood oxygen depends on the cause and severity of the condition. The main goal of treatment is to increase the amount of oxygen in your blood and improve the function of your lungs and heart. Some common treatments include:

Oxygen therapy: This involves giving you extra oxygen through a mask or a nasal cannula (tube) that fits into your nostrils. Oxygen therapy can help relieve symptoms and prevent complications of low blood oxygen. The amount and duration of oxygen therapy depend on your condition and your doctor's recommendation. You may need oxygen therapy only during certain activities, such as exercise or sleep, or you may need it continuously.

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Medications: Your doctor may prescribe medications to treat the underlying cause of low blood oxygen or to relieve symptoms. For example, you may need antibiotics for pneumonia, bronchodilators for asthma or COPD, diuretics for pulmonary edema, anticoagulants for pulmonary embolism, or pain relievers for chest pain.

Surgery: In some cases, you may need surgery to correct the cause of low blood oxygen. For example, you may need surgery to remove a lung tumor or a blood clot, to repair a heart valve or a congenital heart defect, or to perform a lung transplant.

What are the complications of low blood oxygen?

Low blood oxygen can have serious consequences for your health if left untreated. Some possible complications include:

Hypoxia: This is when your tissues do not get enough oxygen to function properly. Hypoxia can affect any organ in your body, but it is especially dangerous for your brain and heart. Hypoxia can lead to brain damage, stroke, heart failure, cardiac arrest, or death.

Pulmonary hypertension: This is when the pressure in the arteries that carry blood from your heart to your lungs becomes abnormally high. Pulmonary hypertension can damage your lungs and heart and make it harder for them to work. Pulmonary hypertension can cause symptoms such as shortness of breath, chest pain, swelling in your legs and abdomen, and fainting.

Cor pulmonale: This is when your right ventricle (the lower right chamber of your heart) becomes enlarged and weak due to pulmonary hypertension. Cor pulmonale can impair the pumping ability of your heart and lead to heart failure.

How can you prevent low blood oxygen?

Some causes of low blood oxygen are not preventable, such as congenital heart defects or genetic blood disorders. However, you can take some steps to reduce your risk of developing low blood oxygen due to other causes, such as:

Quit smoking: Smoking damages your lungs and reduces their ability to transfer oxygen into your blood. Quitting smoking can improve your lung function and lower your risk of lung diseases that can cause low blood oxygen.

Avoid exposure to carbon monoxide: Carbon monoxide is a colorless, odorless gas that can bind to hemoglobin and prevent it from carrying oxygen. Carbon monoxide poisoning can cause low blood oxygen and even death. To avoid exposure to carbon monoxide, install carbon monoxide detectors in your home and car, check them regularly, and replace them when needed. Also avoid using gas stoves, fireplaces, generators, or other sources of combustion in poorly ventilated spaces.

Get vaccinated: Some infectious diseases, such as influenza, pneumonia, and COVID-19, can affect your lungs and cause low blood oxygen. Getting vaccinated can protect you from these diseases and their complications.

Learning about low blood oxygen levels

Low blood oxygen, or hypoxemia, is a significant medical concern that requires prompt attention and treatment. It arises from a variety of causes, including lung and heart diseases, and can lead to severe symptoms and complications if left unaddressed. Diagnosis involves several tests, such as arterial blood gas analysis and pulse oximetry, to measure the oxygen levels in the blood accurately. Treatment is tailored to the underlying cause and may include oxygen therapy, medications, or surgery. Preventive measures, including quitting smoking and avoiding exposure to carbon monoxide, are crucial for those at risk. By understanding the causes, symptoms, and treatment options for low blood oxygen, individuals can seek timely medical care and adopt lifestyle changes to mitigate the risks associated with this condition.


What is the most common cause of low blood oxygen?
The most common cause of low blood oxygen (hypoxemia) is an underlying illness that affects either blood flow or breathing, such as heart or lung conditions. Other factors contributing to hypoxemia include sleep apnea, mild lung diseases, and being at high altitudes​​.

What is the lowest oxygen level you can live with?
While specific thresholds can vary based on individual health conditions and tolerances, generally, a pulse oximeter reading below 90% is considered low (hypoxemia), and urgent medical evaluation is needed. It's crucial to understand that oxygen levels significantly lower than this can be critical and require immediate medical attention​​.

How can I increase my blood oxygen level?
Increasing your blood oxygen level can be achieved through several methods, including breathing fresh air to increase the amount of oxygen your body takes in, quitting smoking to improve circulation and lung function, and practicing breathing exercises like pursed-lip breathing and deep belly breathing to enhance your oxygen intake​​.

What happens when your oxygen level drops to 70?
When oxygen levels drop to 70, it's a critical condition that can lead to severe symptoms and potentially life-threatening complications. Low oxygen levels at this range can impair organ function and lead to conditions such as hypoxia, where there's not enough oxygen for the body's tissues and organs to function properly. Immediate medical treatment is essential to prevent serious outcomes and provide necessary oxygen support​​.

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