Healthy Living

What Is Cyanosis and Why Does It Occur?

What Is Cyanosis and Why Does It Occur?


Cyanosis is the medical term for a bluish discoloration of the skin, nails, toes, and mucous membranes. It is generally caused by low levels of oxygen in the blood. Normally, blood appears bright red when it is fully oxygenated. However, when blood does not have enough oxygen, it turns bluish red or dark purple in color. 

This bluish discoloration manifests in the parts of the body where there is limited oxygen in the blood, such as mucous membranes, skin, and nail beds. Cyanosis happens when fresh oxygen cannot get into the bloodstream or when there is a delay in blood reoxygenation.  

Cyanosis occurs when deoxygenated hemoglobin in the blood reaches 4-6 g/dL. Apparent cyanosis is usually observed when oxygen saturation drops around 80-87 percent. 

Types of Cyanosis

Central Cyanosis

This type of cyanosis is usually due to lung or heart diseases and hemoglobin abnormalities, such as sulfhemoglobinemia or methemoglobinemia. A bluish discoloration is often seen on a person's lips and tongue due to central arterial blood desaturation from respiratory and cardiac disorders. 

In most cases, patients with central cyanosis also have peripheral cyanosis. Other features of central cyanosis also depend on the underlying cause. The feet and hands often have a normal temperature, except when there is a poor peripheral circulation. 

Urgent assessment or hospital admission is required when a person experiences episodes of central cyanosis. An emergency admission is particularly important in young children and infants. 

Peripheral Cyanosis

Peripheral cyanosis is due to poor local circulation and increased oxygen extraction in the peripheral tissues of the body. This type of cyanosis features peripheral vasoconstriction and a bluish discoloration of the affected areas, which are often cold. The bluish discoloration is prominently observed in nail beds, which can be relieved by gently warming the extremity.

Peripheral cyanosis can be caused by the following:

  • Thrombosis or embolism
  • Blood vessel constriction in the fingers, limbs, and toes due to extreme cold weather conditions
  • Raynaud’s disease
  • Acrocyanosis
  • Poor blood flow to the heart, which reduces cardiac output (seen in heart failure or circulatory shock)


Most cases of cyanosis happen due to a lack of oxygen in the blood, which can be caused by the following:

Lung Problems

Problems that affect the airways:

  • Croup (swelling around the vocal cords)
  • Epiglottitis (inflammation of the epiglottis)
  • Choking

Heart Problems

  • Congenital heart defects 
  • Cardiac arrest
  • Heart failure

Other Factors

  • Prolonged seizures
  • Frequent exposure to extreme cold weather, air, or water
  • Drug overdose 


Aside from a bluish discoloration, cyanosis may also be accompanied by varying symptoms, which depend on the underlying disorder. Problems that arise due to circulatory system disorders may also involve other systems of the body. 

Cardiac and respiratory symptoms with cyanosis:

  • Difficulty breathing
  • Shortness of breath
  • Tachypnea (rapid breathing)
  • Leaning the chest forward to easily breathe when sitting
  • Chest pain
  • Squatting in young children
  • Using the rib cage muscle to easily breathe

Other symptoms that occur with cyanosis:

  • Frequent headaches
  • Fever
  • Loss of consciousness 
  • Confusion 
  • Nail clubbing 
  • Poor feeding and poor sleeping habits in young children and infants
  • Fussiness
  • Irritability
  • Lethargy

The following symptoms might indicate life-threatening conditions. Seek immediate medical help if you or another person develop cyanosis along with any of the following symptoms:

  • Difficulty breathing
  • Loss of consciousness
  • Dizziness
  • Fever
  • Numbness or pain in the hands, arms, legs, toes, or fingers 
  • Confusion
  • Chest pain
  • Lethargy
  • Profuse sweating
  • Pale arms, hands, fingers, legs, or toes

Risk Factors

The common risk factors for cyanosis include:

  • Exposure to cold
  • High altitude
  • Congenital heart disease (tetralogy of Fallot, transposition of the great arteries, tricuspid valve disease, pulmonary stenosis, truncus arteriosus, total anomalous pulmonary venous connection)
  • Hemoglobin abnormalities (methemoglobinemia, sulfhemoglobinemia, polycythemia)
  • Carbon monoxide poisoning
  • Impaired exchange of gases
  • Embolism
  • Pulmonary arteriovenous malformations
  • Cold exposure
  • Raynaud's phenomenon
  • Acute severe asthma
  • Pneumonia
  • Lung embolism
  • A long history of COPD
  • Taking certain medications (beta blockers, nitrite or nitrate-containing compounds, dapsone, sulfonamides, benzocaine, chloroquine)
  • Arterial obstruction (peripheral vascular disease, Buerger's disease)
  • Venous obstruction (thromboembolism, deep vein thrombosis, superior vena cava syndrome)
  • Decreased cardiac output (left-sided heart failure, hypovolemia, shock)
  • Neurological disorders (severe head trauma, intracranial hemorrhage, transient tachypnea of the newborn, seizures, brief resolved unexplained event or BRUE, hypoxic-ischemic encephalopathy)


Consult your healthcare provider right away if you develop a bluish skin discoloration or bluish tinge in your fingernails or toenails. Cyanosis is often a sign that something is not right in your body. To help determine the cause of cyanosis, the doctor will initially conduct a physical examination by checking the affected parts of your body and listening to your lungs and heart. A sample of your blood may also be collected for other tests.  

A noninvasive pulse oximeter may also be used by your healthcare provider to measure your blood's oxygenation. Your doctor may also order an arterial blood gas test to measure the levels of pH, oxygen, and carbon dioxide in the blood. To further evaluate your lungs and heart, imaging tests, such as a chest X-ray or a CT scan may be performed as well. 


Treatment usually depends on the cause of cyanosis (e.g., patients who have shortness of breath may receive oxygen). However, you should seek immediate medical help if your hands or feet still remain bluish in color even after warming them up. Treatment for cyanosis usually involves the identification and correction of the underlying cause to effectively restore the flow of oxygenated blood to the affected areas of the body. Limited complications and an improved outcome may result when prompt treatment is received. 

There are also off-label drugs that can be used to help relax the blood vessels in peripheral cyanosis. They include erectile dysfunction drugs, medications for high blood pressure, and antidepressants. An off-label drug is an FDA-approved medication used for a different condition instead of using it for its intended purpose. These drugs can still be prescribed by doctors for their patients as they see fit. 

However, certain medications may cause side effects like blood vessel constriction. They include medications such as:

Heart failure and other potentially life-threatening medical conditions that are associated with cyanosis are considered as an emergency, which requires treatment in a hospital. Long-term lifestyle changes may be required in people with Raynaud’s disease. Smoking and consuming caffeinated products should be avoided since both can cause blood vessel constriction.