A blood culture is a test that checks for foreign invaders like bacteria, yeast, and other microorganisms in your blood. The presence of these pathogens in the bloodstream can be a sign of a blood infection, a condition known as bacteraemia. A positive blood culture results mean that you have bacteria in the blood and the infection involves the blood that travels throughout the system. Bacteria that begin to invade the skin, lungs, urine, or gastrointestinal tract are common sources of blood infections. The infection can spread to the blood and become systemic if it’s severe or if the immune system is unable to contain it and systemic infection is known as sepsis.

Basically, blood culture test comprises a simple blood sample that is analysed in the laboratory and the doctor will evaluate the findings to determine the source of infection and treatment plan.
Blood culture test

Purpose Of Test

Blood culture tests are suggested by the doctor when they suspect that a person may have a blood infection. It is vital to test for any blood infection because it can lead to severe complications like sepsis.

In sepsis, the infection causing pathogens in the bloodstream impede with body’s normal defence mechanism and avert the immune system from functioning well. These pathogens also secrete toxins that may eventually damage vital organs. The test results would help the healthcare provider to determine, which organism or bacteria is causing the infection effective treatment plan.

Symptoms Of Blood Infection /Sepsis

Some of the common symptoms of a blood infection that needs immediate medical help include:


High fever

Rapid breathing

High palpitation

Extreme fatigue

Muscle pain


If left untreated, a blood infection can progress to a more serious stage, sepsis. The symptoms of sepsis in addition to those mentioned above, as well as signs of organ damage such as:


Reduced urine output



Spotted skin

As the infection progresses more severe complications of sepsis may happen, which include

Inflammation throughout body

Formation of several tiny blood clots in smallest blood vessels

A sudden drop in blood pressure

Failure of organs

Also Read: Septic Shock: Causes, Symptoms And Treatment

Certain Health Conditions

Blood culture test can also detect conditions such as endocarditis. It is a condition that develops when bacteria in the bloodstream sticks to the heart valves and can be fatal.

How To Prepare For The Test?

It is important to inform your healthcare provider about the medications you’re taking and any supplements. As the doctor may ask you to stop taking certain medications that may interfere with results.

How Is Test Performed?

The skin is cleaned to avert any microorganisms on the skin from infecting the test. The technician covers a cuff or an elastic band around the arm to let the vein fill with blood and become more prominent. Then a needle is used to draw samples of blood from the arm.

Usually, several blood samples are collected from different veins to help increase the possibility of detecting the bacteria or fungi in the bloodstream. For an adult, the technician may usually draw two or three blood samples, often drawn on different visits.

After drawing the blood, the technician covers the site with a bandage. The blood sample is analysed in the laboratory where it’s cultured. Each sample is added to a bottle containing a liquid called broth which favours any microorganism present in the blood sample to grow.

Interpreting The Results

If the blood culture is positive, it means you have a bacterial or yeast infection in the blood. When the type of organism present in the blood is determined, the doctor will further do another test called a sensitivity test. This test helps to evaluate which medication will work best against that organism. It is a regular protocol to run a sensitivity test as a follow-up to a positive blood culture test. Furthermore, it can also be done when an infection is not responding to treatment.

If the doctor suspects that a person may have a blood infection, then a wide range of antibiotic injections are administered intravenously. These medications can combat a broad spectrum of bacteria, while you’re waiting for the blood culture or sensitivity testing results.

Blood infections need prompt treatment in a hospital or else they can be lethal. As blood infections can lead to severe complications, talk to a doctor if you’re showing any symptoms.