When there is not enough oxygen supply in your bloodstream, the skin or membrane just below the skin may turn a blue or purple color. This is also known as cyanosis.

Cyanosis can be difficult to spot in people with darker skin tones but may appear gray or white. Those with yellow skin tones may see a gray or green appearance.

Blue fingernails can occur for many reasons, including being out in cold temperatures for a long time. This is because the cold causes your blood vessels to constrict, also known as vasoconstriction. This limits the amount of oxygenated blood that can reach your skin, resulting in cyanosis.

The causes of cyanosis can include chronic health conditions, heart disease, and anemia. If you often have blue nails, consider speaking with a healthcare professional to rule out any underlying health conditions.

What are blue fingernails?

Close-up of a person's entwined hands whose fingernails are painted blue. — Lucas Ottone/Stocksy United

Most often, blue fingernails are the result of cyanosis. This can make your nail beds or the skin below your nails look very pale or with a bluish or gray tint.

Another sign that your blue nails are due to cyanosis is the skin on your lips turning a bluish-purple or gray color.

If you notice just one nail is blue, this is more likely to be due to an injury or skin trauma, known as a subungual hematoma.

What are the different types of cyanosis?

There are several types of cyanosis, depending on the severity of the lack of oxygen and the parts of your body that are affected.

The different types of cyanosis include:

Central cyanosis: Also known as general cyanosis, this type can affect your entire body. It is a serious health condition that needs immediate medical care.
Differential cyanosis: This can affect the skin in your lower limbs, like your feet, and can be due to heart and lung health issues.
Peripheral cyanosis: This can cause your fingernails and hands to turn blue or gray. It is rarely fatal.

With all types of cyanosis, the affected area may appear differently depending on your skin tone:

Lighter skin tones: You may notice a bluish tinge.
Darker skin tones: You may see a gray or white appearance.
Yellow skin tones: You may notice a gray or green tinge.

What can cause blue fingernails?

Some health conditions can cause blue fingernails (peripheral cyanosis) to develop. This includes:

Raynaud’s disease: This condition causes your blood vessels to constrict in response to temperatures or emotional events. This lack of blood flow can cause limbs to develop a bluish tinge.
Heart conditions: Several heart conditions like congenital heart disease, heart failure, or heart murmurs can cause blue fingernails. This is because these conditions reduce the amount of oxygenated blood that reaches the vessels in your fingers or toes.
Blood vessel issues: If you have an irregularity in an artery or a condition obstructing your blood flow, like deep vein thrombosis, you may notice blue fingernails.
Lung conditions: Various lung conditions that restrict the efficiency of oxygen into your bloodstream can cause blue fingernails. This includes chronic obstructive pulmonary disorder (COPD), which is a blood clot that starts in the lungs, also known as a pulmonary embolism.

Remember that peripheral cyanosis may be less noticeable on darker skin tones but may appear gray or white. You may see a gray or green appearance if you have a yellow skin tone.

Treatment for blue fingernails

A doctor needs to identify the cause of cyanosis for treatment to be effective. Cyanosis treatment will aim to fix the root issue.

A healthcare professional will examine your hands and feet to check for clubbing, where fingers and toes enlarge. Clubbed fingers can be a clear sign of underlying and severe health conditions, such as congenital heart disease and lung issues.

A doctor will also likely check your heart and breathing to assess for underlying health conditions. If your cyanosis symptoms are severe, a doctor may perform an arterial blood gas measurement. This identifies the amount of oxygen and hemoglobin in your bloodstream. Hemoglobin is the component of your blood cells that carry oxygen around your body.

Depending on the cause of your symptoms, treatments can include:

oxygen support therapy for chronic lung conditions
medications to relax your blood vessels, such as benazepril (Lotensin)
limiting caffeine and nicotine
surgery to correct congenital heart disease

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When to speak with a doctor

Cyanosis is not a health condition but rather a symptom of another health issue. Therefore, if you notice you often have blue fingernails, consider speaking with a healthcare professional.

Cyanosis can be a sign of something serious. If you notice any of the following symptoms alongside cyanosis, seek medical care immediately:

chest pain
difficulty breathing
flu-like symptoms
disorientation
excess sweating

Summary

Blue fingernails, or peripheral cyanosis, can be due to your blood not carrying enough oxygen around your body.

It can also sometimes result from being out in the cold for too long. However, it may also be due to an underlying medical condition, such as congenital heart disease or a lung disorder. Blood vessel irregularities can also cause peripheral cyanosis.

Cyanosis is not a health condition but instead a symptom of another one. Therefore, treatment will focus on the underlying cause and aim to treat that condition first.

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