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Why are my fingernails blue?

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Updated on December 4, 2020

Blue fingernails are commonly caused by cyanosis, which happens when there’s a lack of oxygen in the blood. Blood lacking in oxygen has a bluish tint.

There are 2 types of cyanosis: peripheral and central. Read on to find out more about each of these, as well as what you can do to bring your fingernails back to their normal color.

Peripheral cyanosis

Peripheral cyanosis causes only the skin on your hands and feet to turn blue. It’s the result of decreased blood flow to these parts of the body only.

Cold temperatures

Peripheral cyanosis can be caused by something as simple as cold temperatures. This is because your blood vessels narrow in response to the cold, meaning less blood and oxygen are able to reach the skin.

In this case, your nails should return to their normal color once your hands and feet warm up. You can speed up this process by massaging your hands and feet or running them under warm water.

Raynaud’s phenomenon

Raynaud’s phenomenon, also known as Raynaud’s syndrome, is a condition in which blood supply to specific body parts, particularly the fingers and toes, is temporarily reduced. Sometimes, it can occur without an apparent cause. Other times, it can be caused by cold temperatures or emotional stress.

Blood clots

A blood clot is a clump of blood that forms in deep tissue or within a blood vessel. It can happen as a result of an injury or it can occur spontaneously.

If a blood clot blocks blood supply to your fingers, it can cause a blue tint to appear under your fingernails.

Central cyanosis

Central cyanosis occurs throughout the body. It causes not only your hands and feet to turn blue, but also other areas, like your lips or earlobes. It’s typically a sign of low blood oxygen levels.

Since your lungs are responsible for transporting oxygen throughout your body, lung disorders can contribute to central cyanosis. These may include:

  • Pulmonary embolisms (blood clots in the lung)
  • Lung infections, like pneumonia or whooping cough
  • Chronic lung disorder, such as chronic obstructive pulmonary disease (COPD) or asthma
  • Bronchiectasis (enlargement of parts of the airway)
  • Acute respiratory distress syndrome (ARDS) or neonatal respiratory distress syndrome (NRDS)

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Central cyanosis can also be caused by heart problems, such as:

  • Congenital heart disease
  • Heart failure
  • Cardiac arrest

Problems with airways can also contribute. This can include:

  • Croup
  • Anaphylaxis
  • Epiglottitis
  • Choking

In cases where there is no underlying condition to blame, central cyanosis may be caused by another issue. This includes being at high altitude, where air contains less oxygen, or carbon monoxide poisoning, in which carbon monoxide builds up in your bloodstream.

Diagnosis and treatment of blue fingernails

To diagnose cyanosis, your doctor will measure how much oxygen is in your blood. This is most often done through a non-invasive pulse oximeter. The device goes on the end of your finger and monitors oxygen saturation in your blood.

During your examination, the doctor may ask some questions to help diagnose your condition, such as when the bluish discoloration began, whether you have been exposed to high altitude or cold temperatures, or if you’re having trouble breathing.

Besides providing a treatment plan for the underlying cause of your skin’s hue, your doctor may also take more immediate action towards restoring the amount of oxygen to your blood.


Blue nails are often caused by cyanosis, which happens when there isn’t enough oxygen in the blood. It can be caused by something relatively harmless, like cold temperatures. It can also be caused by underlying health conditions.

If your fingernails are blue and don’t return back to their normal color even when you warm up your hands, talk to your doctor. They can help you figure out the cause and determine a treatment plan.