Low blood oxygen (hypoxemia)

Hypoxemia is a low level of oxygen in the blood. It starts in blood vessels called arteries. Hypoxemia isn't an illness or a condition. It's a sign of an issue tied to breathing or blood flow.

Hypoxemia may lead to:

• Shortness of breath.
• Fast breathing.
• Fast or pounding heartbeat.
• Not thinking clearly.

A healthy level of oxygen in the arteries is about 75 to 100 millimeters of mercury (mm Hg). Healthcare professionals use a sample of blood taken from an artery to measure levels of oxygen and the waste gas carbon dioxide. This is called an arterial blood gas test.

Most often, the first measure is the amount of oxygen that red blood cells carry. This is called oxygen saturation. A medical device that clips to the finger, called a pulse oximeter, measures oxygen saturation. Healthy pulse oximeter values range from 95% to 100%. Values under 90% are low.

Often, hypoxemia treatment involves getting extra oxygen. This treatment is called supplemental oxygen or oxygen therapy. Other treatments focus on the cause of hypoxemia.

The cause of hypoxemia may be:

• Less oxygen in the air you breathe, such as at elevations high above sea level.
• Breathing that's too slow or shallow to meet the lungs' need for oxygen.
• Not enough blood flow to the lungs or not enough oxygen to the lungs.
• Trouble with oxygen getting into the bloodstream and the waste gas carbon dioxide getting out.
• An issue with how blood flows in the heart.
• Changes in the protein called hemoglobin, which carries oxygen in red blood cells.

Causes of hypoxemia that are linked to issues with blood or blood flow include:

• Anemia — a condition in which the body doesn't get oxygen due to a lack of healthy red blood cells
• Congenital heart defects in children — heart conditions that children were born with
• Congenital heart disease in adults — heart issues that adults were born with

Breathing conditions that can lead to hypoxemia include:

• ARDS (acute respiratory distress syndrome) — a lack of air due to a buildup of fluid in the lungs
• Carbon monoxide poisoning
• COPD — (chronic obstructive pulmonary disease) — the blanket term for a group of diseases, including emphysema, that block airflow from the lungs
• Guillain-Barre syndrome — a condition in which the body's immune system attacks the nerves
• Interstitial lung disease — the term for a large group of conditions that scar the lungs
• Myasthenia gravis — a condition that weakens the muscles you control
• Pneumonia — an infection in one or both lungs
• Pneumothorax — a collapsed lung
• Pulmonary edema — too much fluid in the lungs
• Pulmonary embolism — a blood clot in an artery in the lung
• Pulmonary fibrosis — a condition that happens when lung tissue becomes damaged and scarred
• Sepsis — a life-threatening condition in which the immune system reacts too strongly to an infection
• Sleep apnea — a condition in which breathing stops and starts many times during sleep

Some medicines that can make breathing slow and shallow can lead to hypoxemia. These include some opioid pain relievers. Medicines that prevent pain during surgery and other procedures, called anesthetics, also can cause hypoxemia.

You may learn you have hypoxemia when you see a healthcare professional for shortness of breath or another breathing-related condition. Or you might share the results of an at-home pulse oximetry test with your healthcare professional.

If you use a pulse oximeter at home, know that the following can make the results less exact:

• Poor blood flow, also called poor circulation.
• Black or brown skin color.
• Tobacco use.
• Fingernail polish.

If you have hypoxemia, the next step is to figure out its cause.

Seek emergency care if you have shortness of breath that:

• Comes on fast, affects how well you can do daily tasks or happens with symptoms such as chest pain
• Happens at an elevation above 8,000 feet (about 2,400 meters) and comes with a cough, fast heartbeat or weakness. These are symptoms of fluid leaking from blood vessels into the lungs, called high-altitude pulmonary edema. This can be deadly.

See your healthcare professional as soon as you can if you:

• Become short of breath after slight physical effort or when you're at rest.
• Have shortness of breath that you don't expect from a certain activity, given your fitness and health.
• Wake up at night with a gasp or a feeling that you're choking. This may be a symptom of sleep apnea, a condition in which breathing starts and stops during sleep.

Self-care

These tips could help you cope with continued shortness of breath:

• If you smoke, quit. This is one of the most important things you can do if you have hypoxemia. Smoking makes medical conditions worse and harder to treat. For help quitting, talk with your healthcare professional.
• Stay away from secondhand smoke. Don't be around others who smoke. It can cause more lung damage.
• Get regular exercise. Ask your healthcare professional what activities are safe for you. Regular exercise can boost your strength and help you endure hard effort.