If a person's skin or lips turn blue, it's usually caused by low blood oxygen levels or poor circulation. It can be a sign of a serious problem, so it's important to seek medical advice.

When blood becomes depleted of oxygen, it changes from bright red to darker in colour, and it's this that makes the skin and lips look blue.

In darker-skinned people, the blue tinge may be easier to spot in the lips, gums and around the eyes.

The medical name for this blue tinge is cyanosis.

What to do

Call 999 or go to your nearest hospital emergency department (A&E) immediately if you notice an adult or child suddenly turning blue, particularly if they have other symptoms, such as difficulty breathing or chest pain. This could be a sign of a life-threatening problem.

See your GP or call NHS 111 if you have cyanosis that comes on very gradually, or affects just the fingers, hands, toes or feet. This is usually the result of a less serious problem with blood circulation, but it should still be checked by a doctor.

Common causes of cyanosis

Some of the main causes of cyanosis are described below, but you shouldn't use this to diagnose yourself – always leave that to a doctor.

Cyanosis that just affects the hands, feet or limbs

If just the fingers, toes or limbs have turned blue and feel cold, it's known as "peripheral cyanosis". The cause is usually poor circulation resulting from:

Cyanosis that affects the skin generally and/or lips

When all the skin and/or lips have a blue tinge, it's known as "central cyanosis" and is usually a sign of low levels of oxygen in the blood. Common causes for central cyanosis are listed below.

A problem with the lungs:

A problem with the airways:

  • choking – read what to do if someone is choking
  • croup – a childhood condition, usually caused by a virus, that affects the airways and causes a barking cough
  • epiglottitis – inflammation and swelling of the flap of tissue at the back of the throat, usually caused by infection
  • anaphylaxis – a severe allergic reaction that can restrict the airways

A problem with the heart:

  • heart failure – where the heart fails to pump enough blood around the body
  • congenital heart disease – a heart defect present at birth that can affect how blood travels around the heart and body
  • cardiac arrest – where the heart stops beating

Other causes:

Page last reviewed: 29/05/2015

Next review due: 29/05/2017