It's a matter of life and death.

Meaning

The situation is extremely serious, potentially fatal.

Examples

• John: 'The child is choking.'<br>
• Alice: '<b>It's a matter of life and death.</b> We need to perform the Heimlich maneuver!'
• John: '<b>It's a matter of life and death.</b> Call an ambulance immediately!'
• Alice: 'He's bleeding profusely.'<br>