Some causes of lips turning blue can be a lack of oxygen, being exposed to cold or water environments, lung conditions and certain heart issues, states the National Institutes of Health's MedlinePlus. Some other factors that can cause this symptom are certain medications and exposure to a poison such as cyanide. When the skin, fingernails or lips acquire a bluish tint, the condition is called cyanosis.
Certain medical issues, such as a blood clot in the lungs or Raynaud phenomenon, can lead to the lips or skin becoming blue in color. A congenital heart defect can also lead to a symptom such as blue lips, notes the Texas Heart Institute.
Treating cyanosis is dependent on the specific cause. For example, when it is due to cold exposure, it is important to keep the body warm by wearing appropriate clothing when going out into a cold environment. Other causes, such as a blood clot, heart or breathing issues, require medical attention.