Blood Culture and Sensitivity

A blood culture is a test that checks samples of blood for the presence of disease-causing germs like bacteria and fungi. During this test, a blood sample is placed in a special container in a laboratory and watched to see if germs grow.

Blood culture testing is frequently used to diagnose infections and determine if germs have entered the bloodstream. A blood culture test identifies the specific germ causing an infection and enables further testing to determine what type of treatment may be most effective.

Taking a Blood Culture Test

Blood culture testing requires at least two blood samples that are taken from different veins. Multiple samples are used because it provides a more reliable test result. Often, three or four blood samples will be taken.

The blood draws can occur in various medical settings like a doctor’s office, laboratory, or hospital. Patients with severe symptoms from infections may have their blood drawn in an emergency room.

Before the test

There is usually no preparation required to take a blood culture test. However, testing is normally performed before starting antibiotic treatment because these drugs can affect test results. For that reason, you should tell your doctor if you have taken any antibiotics prior to the test.

During the test

It is normal to have between two and four separate blood draws for blood culture testing. Samples may be obtained at the same time, or two initial samples may be drawn with additional blood samples taken several hours later.

Blood samples are usually taken from veins in the arms. For each blood draw, a health care professional will tie an elastic band around your arm to increase blood flow in the vein. The skin will then be thoroughly cleaned with an antiseptic, which is an important step in making sure that bacteria from the skin do not contaminate your blood sample.

A needle will be inserted through the skin and into the vein, which may cause a brief stinging sensation. Blood will be withdrawn into a vial, and once enough blood is collected, the needle will be removed. The same process will be repeated for each blood sample that is needed. Each blood draw usually takes less than a few minutes.

After the test

A bandage or gauze will typically be applied to each area where your blood was drawn. You may notice some bruising or soreness around the puncture sites, but these effects usually go away quickly.

Serious complications from a blood draw are rare, but make sure to tell your doctor if you have any persistent or severe side effects after your blood culture test.