what is a blood infection
Last updated September 6, 2026.
**A blood infection means bacteria, or less often fungi or viruses, have gotten into your bloodstream, and because blood reaches every organ, it can make you sick very quickly.** Doctors call germs in the blood bacteremia or septicemia, and the infection usually starts somewhere else first, such as the lungs, urinary tract, skin, gut, or an IV line. If your body's response to that infection begins damaging your own organs, it is called sepsis, which is a medical emergency. Warning signs include fever or shivering, a fast heart rate, fast breathing, confusion, low blood pressure, clammy skin, and pain that feels worse than any you have had. Diagnosis relies on blood cultures and other lab tests, and treatment is IV antibiotics, fluids, and hospital monitoring, started as fast as possible. You lower your risk by keeping wounds clean, staying current on vaccines such as flu, COVID-19, and pneumococcal, and treating infections early.
What to do
- Treat the source infection: Finish the full course of antibiotics for a urine, lung, skin, or dental infection instead of stopping when you feel better.
- Watch a wound daily: Growing redness, streaking, warmth, pus, or new fever means the infection is spreading and needs to be seen the same day.
- Know the emergency signs: Confusion, severe shortness of breath, a racing heart, shivering with high fever, or skin that is clammy and mottled means call 911.
- Say the word sepsis: Tell the clinician you are worried about sepsis and mention any recent infection, surgery, or catheter, since that speeds up testing.
- Protect higher-risk people: Adults over 65, infants, people with diabetes, cancer, or a weak immune system get sicker faster and should be checked sooner.
- Stay current on vaccines: Flu, COVID-19, pneumococcal, and RSV shots prevent infections that commonly lead to bloodstream infection.
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