Hypoxemia (Low Blood Oxygen): Symptoms, Causes, Treatments

Hypoxemia occurs when you don’t have enough oxygen in your blood. The hemoglobin molecules in your red blood cells don’t carry as much oxygen as they should, and your body doesn’t get the amount of oxygen it needs for everyday functions.

Several factors can cause hypoxemia, including sleep apnea, lung disease, other chronic lung conditions, and heart problems. If left untreated, hypoxemia can lead to serious health problems, so it’s essential to get medical help and get to the root of the issue.

Hypoxia Vs. Hypoxemia

Hypoxia and hypoxemia are two distinct problems.

Hypoxia is when oxygen levels in your tissues (muscles, organs, etc.) are too low, usually caused by hypoxemia.

Hypoxemia is the term for when the oxygen levels in your blood, specifically the arteries, are below normal. Breathing and circulation issues can lead to hypoxemia, which can lead to serious symptoms and even hypoxia if not treated.

You can have hypoxemia without developing hypoxia, particularly if you’ve only had low blood oxygen levels for a short period. In most cases, however, patients have both hypoxemia and hypoxia at the same time.

Blood oxygen levels are usually described as either a percentage of oxygen saturation (where 100% is fully saturated) or as the partial pressure of oxygen (PaO2) in the blood (given in mm Hg).

What is a dangerously low oxygen level? A dangerously low oxygen level is anything below 90% oxygen saturation. Anything below 95% oxygen saturation (80 mm Hg) should be brought to the attention of a medical professional.

Symptoms Of Hypoxemia

Most symptoms of hypoxemia happen because the brain and other parts of the body aren’t getting the oxygen they need.

What are the symptoms of low oxygen levels? The symptoms of low oxygen levels are:

  • Shortness of breath
  • Fast breathing
  • Labored breathing (dyspnea)
  • Coughing and wheezing
  • Headache
  • Increased heart rate
  • Mouth breathing
  • Cyanosis, or blue coloration of the skin, lips, and fingernails
  • Confusion

If you experience these symptoms, particularly if they appear without any strenuous activity, contact a medical professional as soon as possible. Untreated hypoxemia can be life-threatening.

Types Of Hypoxemia

Low oxygen levels in your blood and tissues can be triggered by a number of factors. There are several mechanisms of hypoxemia, which can be broken down into different categories.

The primary types of hypoxemia are:

  • Hypoventilation
  • Shunt
  • Low environmental oxygen
  • Diffusion impairment
  • Ventilation/perfusion mismatch


If your lungs don’t fill up with enough air, they can’t get the oxygen they need to deliver to the rest of the body, which is what happens in hypoventilation. Hypoventilation happens when breathing is too slow or shallow to exchange oxygen and carbon dioxide effectively.


In a shunt, blood bypasses the lungs by traveling directly from the right side of the heart to the left. Shunts usually happen due to:

  • Pneumonia
  • Swelling in the lungs (pulmonary edema)
  • Alveolar (microscopic lung air sacs) collapse
  • Acute respiratory distress syndrome (ARDS)
  • Some congenital anatomical abnormalities.

Low Environmental Oxygen

There’s less oxygen in the air at high altitude, so blood oxygenation slows down. Low environmental oxygen can lead to hypoxemia if you don’t breathe faster or more deeply to compensate.

Diffusion Impairment

Diffusion impairment happens when it’s difficult for oxygen to travel from the alveoli to the blood. This usually happens when the alveoli are damaged, there’s lots of inflammation in the lungs, or a patient has lung problems like emphysema.

Ventilation/Perfusion Mismatch

Sometimes the lungs and blood can’t work together to deliver enough oxygen to the body, called a ventilation/perfusion mismatch.

There are two primary causes of ventilation/perfusion mismatch:

  1. The blood flows through the capillaries in the lungs too slowly, so it can’t pick up enough oxygen
  2. There’s good blood flow, but the lungs aren’t taking in enough air

What is the most common cause of hypoxemia? The most common cause of hypoxemia is ventilation/perfusion mismatch, where the lungs don’t deliver oxygen to the blood properly.


Many factors and health problems can lead to hypoxemia. Anything that impairs your ability to breathe has the potential to restrict how much oxygen your lungs can take in, which puts you at risk of developing hypoxemia.

The most common causes of hypoxemia include:

  • Asthma
  • Sleep apnea
  • Pneumonia
  • Bronchitis
  • Chronic obstructive pulmonary disease (COPD)
  • Emphysema
  • Acute respiratory distress syndrome (ARDS), including ARDS caused by the novel coronavirus (COVID-19)
  • Pulmonary edema
  • Pulmonary embolism (blood clot in the lungs)
  • Anemia
  • Certain medications that affect breathing, like narcotics
  • Congenital heart problems

The majority of patients with hypoxemia have trouble breathing, either due to direct problems with their lungs or other issues with their airway, like asthma and sleep apnea. Either way, the effects are similar: your body doesn’t get the oxygen it needs.

Diagnosis And Treatment

It’s essential to diagnose and treat hypoxemia as soon as possible. Left untreated, hypoxemia can progress into acute hypoxemic respiratory failure (AHRF), leading to serious health problems and even death.

Diagnosing Hypoxemia

Hypoxemia is usually diagnosed using pulse oximetry. A pulse oximeter is a device that uses light to measure the amount of oxygen in your blood. This diagnostic tool clips onto your finger, toe, or earlobe and painlessly monitors blood oxygen levels.

In certain medical settings, including in some critical care situations, doctors use arterial blood gas (ABG) measurements to measure arterial oxygen levels as well as pH and blood carbon dioxide levels.

ABG tests involve sampling and testing arterial blood directly. It’s more invasive but more accurate than pulse oximetry.

If your blood oxygen levels are low, your healthcare provider will want to start treatment quickly.

Treating Hypoxemia

Initial treatment of hypoxemia is generally straightforward: medical professionals give hypoxemic patients supplemental oxygen therapy. Supplemental oxygen helps increase oxygen delivery by the lungs into the blood, which is then carried to tissues throughout the body.

If supplemental oxygen doesn’t help reverse the hypoxemia and hypoxia, the patient may require mechanical ventilation. Mechanical ventilation makes sure the patient is breathing fast enough and deep enough to properly oxygenate their blood.

When hypoxemia occurs because a patient has trouble breathing, doctors can prescribe medications (like inhalers for patients with asthma) or devices (like a continuous positive airway pressure, or CPAP, device, or oral appliances) to help keep their airway open.

Once medical professionals have solved the immediate problem of hypoxemia and have raised the patient’s blood oxygen levels, they need to find out why the patient had low blood oxygen in the first place.

The most effective way to combat hypoxemia is to treat its root cause. If you can make sure the lungs are delivering oxygen to the blood and that the blood is delivering that oxygen to the body, you’ll eliminate the hypoxemia and hypoxia.

What happens if hypoxemia goes untreated?

If hypoxemia isn’t treated, it can lead to significant health problems. Your body needs oxygen to stay alive, and there are severe consequences if your lungs aren’t delivering enough oxygen to your body.

Eventually, hypoxemia will lead to hypoxia. Organs and tissues are damaged if they don’t receive sufficient oxygen for an extended period. The brain and liver typically experience problems first, but eventually, all organs will be affected.

Even if it doesn’t damage your organs, chronic hypoxia can have adverse effects on your health. It can lead to high blood pressure in the lungs, which is linked to lung disease.

Sleep Apnea And Hypoxemia

Patients with sleep apnea often experience episodes of hypoxemia. During apneic episodes, the airway becomes blocked, the lungs don’t get enough air, and oxygen doesn’t make it into the blood, which leads to hypoxemia and even hypoxia.

In fact, many of the most disruptive side effects of sleep apnea, like cognitive problems, heart disease, and even liver disease, happen because the body and brain don’t get enough oxygen. Even short periods of hypoxemia during sleep can be dangerous.

Unaddressed sleep apnea can lead to a suite of dangerous health problems, including:

  • Sleep deprivation
  • Difficulty concentrating
  • Headaches
  • Tooth grinding, which can lead to oral health problems and jaw pain
  • Type 2 diabetes
  • Cardiovascular disease
  • Liver disease
  • Depression
  • Cognitive impairment

Uncontrolled sleep apnea can cause additional problems in children, including difficulty learning and ADHD-like symptoms.

Treating Sleep Apnea

It’s relatively easy to treat sleep apnea. Most cases of sleep apnea are cases of obstructive sleep apnea, which is caused by a narrow or blocked airway. Keeping the airway open treats the root cause of the apneic episodes, eliminating sleep apnea at its source.

There are many effective treatments for sleep apnea that help the airway stay open as you sleep, including:

  • CPAP and other similar devices
  • Oral appliances that help position the jaw and tongue
  • Surgery to reduce or remove enlarged soft tissues that block the airway, like the adenoids and tonsils
  • Nerve stimulation to help the tongue stay in the correct position during sleep

Obstructive sleep apnea is an airway health problem, and dentists are airway health experts. Working with a biological dentist like the dental professionals at Rejuvenation Dentistry will help you find the most effective treatments to treat your hypoxemia caused by sleep apnea.

Battling sleep apnea? Find solutions.

Concerned you might have sleep apnea? If you snore loudly at night, grind your teeth, feel incredibly tired even after a full night’s sleep, or have frequent trouble concentrating, you might have it.

Thankfully, it’s easy to test for sleep apnea from the comfort of your own home. At Rejuvenation Dentistry, we offer at-home sleep apnea tests that make diagnosing sleep-disordered breathing a breeze.

We would be happy to evaluate your symptoms in the office or virtually. Click here to make an appointment at our East Hampton or Manhattan offices. We look forward to helping you overcome your sleep apnea-induced hypoxemia.

Dr. Gerry Curatola is a renowned biologic restorative dentist with more than 40 years of clinical practice experience.

He studied neuroscience at Colgate University and attended dental school at the New York University (NYU) College of Dentistry where he now serves as Adjunct Clinical Associate Professor in the Department of Cariology and Comprehensive Care.