Why Are My Fingernails Blue?

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If you’ve ever noticed that your fingernails tend to turn blue—popularly known as “blue finger syndrome”—it might be because you have a condition known as cyanosis. These blue and purplish nails are the result of a lack of oxygen in your bloodstream. The discoloration from cyanosis can affect everyone from adults to children, even newborns.

This change in color can signify you have abnormal hemoglobin, the protein that carries oxygen to your blood cells. This may come from other conditions that impact your respiratory, cardiovascular and central nervous systems.

Beyond this, cold temperatures can also lead to purple nails. Your blood vessels narrow once temperatures drop, preventing enough oxygenated blood to reach the tips of your fingers.

The cause can vary depending on where the discoloration is on the body, how long it lasts and whether or not you have any other underlying medical conditions that may or may not have been diagnosed already.

Cyanosis can affect everyone from adults to children.


Rowan Jordan / Getty Images

Types of Cyanosis

Cyanosis is a symptom of hypoxemia, which occurs when you haven’t received enough needed oxygen in your blood. This is often in people with advanced chronic obstructive pulmonary disease (COPD), but can also be due to conditions like sleep apnea, pneumonia or asthma, among others.

Hypoxia is diagnosed by measuring blood oxygen levels through an arterial blood gas test (ABG) or pulse oximetry, using a sensor that measures the oxygen in your blood.

Cyanosis and its related purple and blue skin discolorations develop when arterial blood oxygen levels drop below 85%.

There are different types of cyanosis: 

  • Central cyanosis means you’ll see an area of bluish discoloration on the body and around mucous membranes. This is the result of a lack of oxygen traveling to your blood cells and other conditions that result in deoxygenated hemoglobin as well as the presence of abnormal hemoglobin. This could indicate you have serious respiratory illness like asthma or pulmonary hypertension. 
  • Peripheral cyanosis refers to bluish tinge found on your hands, toes, and fingertips. This is usually not life-threatening but could suggest another underlying condition. It can be an extension of central cyanosis, which might indicate more serious additional health conditions.
  • Differential cyanosis shows up as asymmetrical bluish discoloration, with your lower extremities being blue and your upper extremities pink. This can mean you might have a serious underlying cardiopulmonary condition.

Cyanosis in Newborns

Cyanosis can be found in infants and young children. Peripheral cyanosis can be a benign discoloration of the baby’s feet and hands. Transient central cyanosis is common and can often clear away within five to 10 minutes of birth. Central cyanosis that lingers on however can be serious. Discoloration of the lips and tongue and could indicate the baby has not received sufficient pulmonary blood flow or oxygen intake, among other serious concerns.


Separate from these other types of cyanosis is pseudocyanosis. This is when blue discoloration results from outside causes that can mimic that of a lack of oxygen to the body’s blood. For instance, there have been examples of the ingesting of metals like iron causing this.

Additionally, consuming certain drugs and toxins can cause the body to mimic the peripheral and central cyanosis from lack of oxygenation in the bloodstream.

Cyanosis Symptoms

Just to be clear, cyanosis is not a disease, but a symptom of other conditions. Your blood transitions from a healthy bright red to a darker red color when it is deprived of needed oxygen. When this happens, your blood will absorb more light from the blue spectrum, leaving your skin to have that blue tinge.

While your fingernails are one of the most common areas of the body where the effects of cyanosis will be most clear, other parts of the body can be impacted. This includes your tongue, lips, skin, ears and gums.

This exact location of the discoloration can give you a clue as to what the underlying cause of your cyanosis might be. Here are some examples: 

  • Central cyanosis will lead to blue coloring of the mucous membranes and extremities. 
  • Peripheral cyanosis will show itself in your lips, hands, fingertips, and toes, but not the mucous membranes. 
  • Differential cyanosis impacts the area between the lower and upper extremities, but not your fingertips, for instance.

Your skin’s temperature can also indicate what type of cyanosis is affecting you. Your temperature might be more normal with central cyanosis but cooler with peripheral cyanosis. Why? This is due to decreased local circulation.

If the blue and purplish discoloration is accompanied by other symptoms like finger clubbing, chest pain, or breathing difficulties, it can help pinpoint what underlying cyanosis you have.

When to Call a Doctor

You should call 911 or seek emergency medical care if your cyanosis symptoms are accompanied by:

  • Chest pain
  • Profuse sweating
  • Clammy skin
  • Shortness of breath
  • Difficulty breathing
  • Dizziness or fainting

These could all be signs of a medical emergency like a heart attack or pulmonary embolus. 


If you have cyanosis and notice your fingertips or other areas of your body are showing signs of a blue or purple discoloration, it could be a sign of a more serious underlying condition or it might mean nothing at all.

Cyanosis is highly variable. Your fingernails might turn blue just temporarily once exposed to a quick shift to colder temperatures that cause your blood vessels to constrict.

More serious underlying conditions can show themselves in the form of persistent cyanosis as a result of either a lack of oxygen sent to the blood, a restriction of blood flow in your blood vessels, or a reduction in cardiac output. These would signify more serious health problems that would need the attention of your physician and medical team. 

Here are some of the key causes of cyanosis, broken down by organ system in the body:

Organ System



Asthma, bronchiolitis, COPD, croup, high altitude, extensive pneumoniainterstitial lung disease (ILD), pulmonary edema, pulmonary embolism


Congenital heart disease, congestive heart failure, shock

Blood vessels

Cold exposure, peripheral artery disease, pulmonary arteriovenous malformations, Raynaud's phenomenon

Blood cells

Carbon monoxide poisoning, methemoglobinemia, polycythemia vera, sulfhemoglobinemia


When aiming to diagnose cyanosis, your doctor will break the process up in three steps:

Physical Exam

Your doctor will determine whether you are exhibiting signs of central, peripheral or differential cyanosis. They’ll check your skin temperature. Cooler temperature suggests impaired local circulation and peripheral cyanosis, while a normal temperature suggests central cyanosis.

They’ll check for finger clubbing, which could suggest congenital heart disease, bronchiectasis and chronic lung infection. You’ll be assessed for any other cardiac or respiratory symptoms.

Review of Medical History

Your doctor will check your family history. You’ll also be asked about the timing of the onset of your symptoms. This will help a physician how and when this might have started and even determine whether this is congenital or an acquired condition. 

Blood Oxygen

They will perform blood oxygen tests in the form of arterial blood gas (ABG) tests, which show the partial pressure of dissolved oxygen in your blood and saturation of hemoglobin levels. They’ll also conduct a pulse oximetry, which will measure the absorption of light at the two wavelengths that correspond to oxyhemoglobin and deoxyhemoglobin.

A pulse oximetry needs to be done with an ABG test since it can have a false-positive reading in people with peripheral cyanosis. This is due to the fact that abnormal hemoglobin levels are not picked up by a pulse oximetry test. Combining the two will give the most accurate assessment possible.

Additional tests and imaging studies might be performed beyond these three assessments. This might be due to your physician’s initial findings and to confirm suspected causes for your cyanosis. 

A Word From Verywell

As you can tell, that blue tinge on your fingernails or elsewhere on your body could before a variety of causes. Cyanosis is highly varied and treatment for it is based on the underlying cause. Cyanosis is not a disease in and of itself. 

The skin discoloration associated with cyanosis might just be a temporary event brought about by cold weather. That being said, this shouldn’t be brushed aside as an unimportant health concern if. You don’t know the cause.

As with any other strange, unusual symptom you might experience, please consult a doctor. Do this even if your cyanosis resolves on its own. Persistent cyanosis suggests a more serious medical condition and should be investigated through proper medical attention. 

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