Causes of septic shock 

Septic shock can be caused by an infection in any part of the body that's left untreated.

The infection will first cause a response from the body known as sepsis.

Bacterial infections are the most common cause of sepsis. Fungi, such as candida, and viruses can also sometimes lead to sepsis, although this is rare.

Bacterial infections happen if harmful bacteria enter the blood through the skin  for example, after an intravenous drip or catheter has been inserted. Sepsis can also occur after an infection in an organ, such as a urinary tract infection (UTI), or a lung infection (pneumonia).

How septic shock develops

Left untreated, the toxins produced by bacteria can damage the body’s cells. They attack the walls of the small blood vessels, causing them to leak fluid from the blood into the surrounding tissues. It can also decrease the heart's ability to pump blood to the organs, which lowers your blood pressure.

The fall in blood pressure means the heart can't supply the body’s vital organs with oxygen-rich blood. Without a blood supply, the brain, heart, kidneys and liver can't function properly.

The fall in blood pressure, which doesn't respond to treatment with fluids, is what distinguishes septic shock from severe sepsis.

At-risk groups

Certain groups of people have an increased risk of developing septic shock. This is because they have weakened immune systems, which reduces their ability to fight serious infections, and includes:


Page last reviewed: 18/02/2015

Next review due: 18/02/2017