Blue nails may indicate that the blood is not carrying enough oxygen to the fingertips. There are many possible causes, some of which are serious. Therefore, a person with blue nails should speak with a doctor to determine the underlying cause.

In some cases, fingernails turn blue or purplish because of cyanosis, which can also affect the lips and skin.

Cyanosis can occur if the blood is not carrying enough oxygen to the fingertips or the person has poor circulation. It can also result from problems with hemoglobin, a protein in the red blood cells that is responsible for carrying oxygen.

Various health conditions that affect the respiratory and cardiovascular systems may also cause cyanosis.

A person who notices that they have blue nails should contact a doctor for advice to rule out any underlying medical conditions.

This article looks at the conditions that can cause blue nails and explains how doctors diagnose and treat cyanosis. It also discusses when an individual should seek help.

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If just one nail is blue, this is likely due to an injury causing blood to collect under the nail.

When all the nails are blue, this indicates cyanosis, which is a symptom of another condition rather than a condition in itself. Blue nails occur because there is not enough oxygen in the blood.

Blue nails may also occur if the circulatory system is not carrying the blood around the body as it should, resulting in poor circulation and a blue tinge.

Cold weather can cause poor circulation temporarily, as the blood vessels narrow because of the reduced temperatures. They do this to prevent the blood from reaching the extremities and to keep the internal organs at the optimal temperature.

If a low temperature is the cause, the normal nail color should return when the person warms their hands.

Blue nails show that the fingers, toes, or both are not getting enough oxygen.

The following conditions can cause cyanosis:

Lung diseases

Various lung conditions can result in the nails developing a blue tinge. These conditions include:

  • Chronic obstructive pulmonary disease (COPD): COPD is an umbrella term for a group of progressive lung diseases that include emphysema and chronic bronchitis. Emphysema destroys the air sacs in the lungs, whereas bronchitis causes inflammation and narrowing of the bronchial tubes, leading to a buildup of mucus. About 30 million people in the United States are living with COPD.
  • Asthma: Asthma causes the airways to narrow and swell, and it may also increase mucus production, potentially leading to a buildup. People with asthma may have trouble breathing, chest pain, a cough, and wheezing that can interfere with their daily life. Sometimes asthma can lead to life threatening asthma attacks.
  • Acute respiratory distress syndrome (ARDS): Individuals with ARDS have difficulty breathing, and their breathing rate and heart rate are faster than normal, leading to a drop in the blood’s oxygen. Doctors treat ARDS with oxygen therapy to improve blood oxygen levels.
  • Pneumonia: Bacteria, viruses, and fungi can all cause pneumonia, which is an infection of the lungs. Following a severe flu infection, for example, pneumonia may develop. The symptoms can vary from mild to severe, but most people recover from pneumonia in 1–3 weeks.
  • Pulmonary embolism (PE): If one of the arteries in the lungs becomes blocked by a blood clot, this can cause PE. Usually, the clot travels from the leg or another part of the body and causes a life threatening blockage of blood flow to the lungs.

Heart diseases

Some cases of blue nails might be due to a heart condition, such as:

  • Congenital heart disease: Babies can be born with abnormal heart and blood vessels. Although some cases will be asymptomatic, others will cause life threatening symptoms.
  • Eisenmenger’s syndrome: This rare disorder affects the heart and lungs and is often a late complication of congenital heart disease. Eisenmenger’s syndrome causes high blood pressure and an abnormal flow of blood through the heart.
  • Congestive heart failure: Heart failure causes problems with the heart, leaving it unable to pump blood as it should. Symptoms include shortness of breath, extreme fatigue, and swollen extremities.

Blood cell and vessel abnormalities

Some issues relating to the blood cells and vessels can also cause blue nails. These include:

  • Methemoglobinemia: This condition causes increased levels of methemoglobin, a form of hemoglobin that cannot release oxygen. People can have this condition from birth or develop it because of exposure to certain chemicals or to medicines such as antibiotics and local anesthetics.
  • Carbon monoxide poisoning: Carbon monoxide blocks hemoglobin’s oxygen-binding capabilities.
  • Polycythemia vera: This form of blood cancer causes the bone marrow to produce too many blood cells.
  • Raynaud’s phenomenon: People with this condition have decreased blood flow to the hands and feet due to blood vessel spasms.

A doctor will diagnose cyanosis by performing a physical exam to look at the blue nails and check for finger clubbing. Clubbed fingers can indicate congenital heart disease and lung problems.

The doctor may also assess the individual for cardiac or respiratory symptoms.

Blood oxygen tests are an essential aid in diagnosing cyanosis. A doctor will take some blood to measure the arterial blood gas (ABG), which shows the blood’s oxygen and hemoglobin levels.

They may also place a device called a pulse oximeter on the individual’s finger to measure the blood’s oxygenation. These tests help determine why someone has blue nails.

As cyanosis is a symptom of an underlying condition, the goal is to treat the cause.

Depending on the cause of blue nails, treatments may include:

  • surgery to correct congenital heart disease
  • supportive oxygen therapy
  • methylene blue for methemoglobinemia
  • medications to help the blood vessels relax, including antihypertensive drugs and erectile dysfunction drugs

Doctors may advise people with Raynaud’s phenomenon to make long-term adjustments to their everyday habits, such as avoiding caffeine and nicotine.

The treatment of cyanosis is challenging, and different specialist doctors and medical teams may need to work together to manage the condition.

It is not uncommon for the nails to appear blue in cold conditions, but they should return to the normal color once the person has warmed up.

If blue nails are not likely due to a low temperature, and the color persists, it is important to seek medical attention.

Doctors will identify and correct the underlying cause of the cyanosis and treat it to restore optimal blood flow around the body.

Receiving treatment promptly should limit the possibility of any complications and improve the person’s outcome.

If someone with blue nails also has symptoms such as chest pain, shortness of breath, profuse sweating, and dizziness, they should immediately call 911. These symptoms can indicate a medical emergency.

Cyanosis is the medical term for blue nails, although it can also affect the lips and skin.

In low temperatures, the nails may appear blue, as the body constricts the circulation to protect the internal organs.

Cyanosis may also be a symptom of a more serious health condition, such as a heart, lung, or blood vessel disorder.

People should seek medical attention to determine the cause of the blue nails so that they can receive prompt treatment.