What is sepsis, and why is it so dangerous?
Sepsis is the body's own response to an infection going wrong and damaging its own tissues and organs. It is not a specific infection — it is what can happen with almost any infection, anywhere in the body.
The mechanism. Normally, the immune system mounts a contained response to an infection. In sepsis, that response becomes dysregulated and systemic: widespread inflammation, blood vessels leaking and dilating, abnormal clotting in small vessels, and falling blood pressure. Organs are deprived of adequate blood flow and begin to fail. Septic shock is the stage where blood pressure cannot be maintained despite fluids.
Why it is so dangerous:
It moves quickly. Deterioration can occur over hours, not days.
Early signs resemble ordinary illness — feeling unwell, feverish, confused — so it is missed.
Mortality rises with every hour that treatment is delayed, which is the basis for treating it as a time-critical emergency comparable to a heart attack or stroke.
Any infection can cause it, including ones that seemed minor — a chest or urine infection, a skin wound, a bite, a post-surgical infection.
The signs to know. UK Sepsis Trust and NHS guidance highlight seeking emergency help if someone has an infection and develops:
Slurred speech or confusion
Extreme shivering or muscle pain
Passing no urine in a day
Severe breathlessness
A feeling that they are going to die
Skin that is mottled, discoloured, very pale or blue — including lips or tongue.
In children, additional signs include breathing very fast, a fit or convulsion, a rash that does not fade when pressed, being very lethargic or difficult to wake, and feeling abnormally cold.
What to do. Call 999 or go to A&E, and say the word "sepsis" — the phrase "I am worried about sepsis" is explicitly encouraged because it triggers assessment pathways.
Who is at higher risk: the very young and very old, pregnant and recently pregnant women, people with weakened immune systems or chronic conditions, and anyone with a recent wound or surgery.
This is general information, not a substitute for urgent medical assessment.