Bacteremia Causes and Diagnosis

Bacteremia is an infection, caused by bacteria, that enters the bloodstream. It may also be referred to as septicemia, sepsis, septic shock, blood poisoning, or bacteria in the blood.

Nurse writing on clipboard and patient with bacteremia in hospital bed in the background
Martin Barraud / Getty Images


Bacteremia typically starts with a small, localized infection, such as an infected incision, a urinary tract infection or another type of infection. Sometimes the individual doesn't even know where the infection was in the early stages, as they didn't notice any signs or symptoms of infection while the infection was in one location.

For an example, we will say the individual has an infected tooth. At first, the patient feels a minor toothache. Then, as the infection continues, the toothache becomes more and more painful. Before he can get an appointment with the dentist, the patient notices a bad taste in his mouth, caused by pus-forming around the tooth. He tries to use mouthwash and takes ibuprofen for the pain, but it continues to get worse.

He knows he needs treatment, but decides he can wait until the next day for his scheduled dental appointment. The next day comes and the patient feels much sicker, is having a fever and chills, and starts to feel exhausted as the worsening infection enters the bloodstream.


When the infection spreads to the bloodstream, it has a new name: bacteremia. Bacteremia simply means bacteria in the blood. This condition is better known by other more common but much scarier names: sepsis and septicemia. The body will continue to try to fight the infection, but the infection is widespread at this point, moving through the bloodstream to the entire body.

At this point, a variety of blood tests including a procalcitonin level will show that the body is responding to the foreign bacteria, typically with an immune response and blood cultures will show the presence of bacteria. This is a very crucial time in the treatment of the infection as bacteremia is far more likely to cause a serious or even life-threatening illness as the body attempts to fight off the infection.

A localized infection can cause serious problems, but an infection that is moving through the bloodstream is far more likely to lead to serious illness. The sooner treatment is started, the more likely the individual is to avoid the even more serious condition of septic shock.

A Precursor to Septic Shock

An infection that begins to travel in the bloodstream can be life-threatening and must be treated aggressively with antibiotics to prevent sepsis from worsening and turning into septic shock. 

Septic shock is a condition where the body is overwhelmed by the bacteria and subsequent infection in the bloodstream.The body struggles to fight off the infection and is unable to continue the normal and essential tasks that the body normally handles with minimal difficulty. When septic shock happens the patient will need typically need medications to increase blood pressure, IV antibiotics, fluids and possibly a ventilator to assist with breathing. These patients are typically cared for in the ICU where constant monitoring is possible.

A Word From Verywell

Bacteremia is a very serious condition and should be treated as quickly as possible once diagnosed. In a nutshell, bacteremia can typically be prevented by not ignoring minor infections such as skin infection or a urinary tract infection. However, even with treatment, some infections will spread, making close monitoring of symptoms, such as temperature, important for an early diagnosis of this potentially life-threatening condition.

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Jennifer Whitlock, RN, MSN, FN
Jennifer Whitlock, RN, MSN, FNP-C, is a board-certified family nurse practitioner. She has experience in primary care and hospital medicine.