Observe the color of the nails.
Blue fingernails are caused by a low level or lack of oxygen circulating in your red blood cells.
It occurs when there isn’t enough oxygen in your blood, making the skin or membrane below the skin turn a purplish-blue color.
The skin discoloration could also mean that there’s a high level of an abnormal form of hemoglobin in your blood.
Cold temperatures can also cause your fingernails to turn blue. That’s because cold temperatures force your blood vessels to constrict. The narrow pathways make it difficult for enough oxygen-rich blood to get to your nails.
If normal nail color returns upon warming up or massaging your hands, the blue color was likely due to that part of your body not getting enough blood supply because of cold temperatures.
Blue discoloration of your fingernails can be caused by problems in the lungs, heart, blood cells, or blood vessels.
Conditions that can cause cyanosis include:
- chronic bronchitis
- emphysema
- asthma
- acute respiratory distress syndrome
- pneumonia
- pulmonary embolism (blood clot in the lung)
- congenital heart disease
- Eisenmenger’s syndrome
- congestive heart failure
- Raynaud’s phenomenon
- carbon monoxide poisoning
- polycythemia vera (production of too many red blood cells)
Call an ambulance if your blue fingernails are accompanied by:
- shortness of breath, breathing difficulties, or gasping for air
- chest pain
- profuse sweating
- dizziness or fainting
Source:
https://www.healthline.com/health/blue-fingernails#causes
