Blood Culture

Written by Brian Krans | Published on August 7, 2012
Medically Reviewed by Brenda B. Spriggs, MD, MPH, FACP

What is a Blood Culture?

A blood culture is a fairly routine test that checks for bacteria, yeast, and other microorganisms in the blood.

The test is relatively simple for the patient and involves a simple blood draw. A laboratory tests the blood sample and the results are forwarded to your doctor.

Why a Blood Culture Is Done

Blood cultures are ordered when a doctor suspects you may have a blood infection. Some blood infections can be mild, but one such serious consequence of a blood infection is sepsis. In this condition, the organisms release toxins that trigger the immune system to attack the body.

Symptoms of sepsis include:

  • chills
  • confusion
  • decreased urine
  • fever
  • nausea
  • rapid breathing
  • rapid heartbeat

The results of the test can help your doctor determine which specific organism or bacteria is causing the problem and how best to combat it.

The Risks of a Blood Culture

The only risk of the test is when you give blood; however, blood draws are routine procedures and rarely cause any serious side effects.

The risks of giving a blood sample include:

  • bleeding under the skin (hematoma)
  • excessive bleeding
  • fainting
  • infection

How to Prepare for a Blood Culture

The test requires little preparation for the patient.

Tell your doctor what kinds of medication you are taking, including prescriptions and nutritional supplements. He or she may ask you to stop taking certain medications that may alter the blood culture results.

If you’re wary of needles, talk to your doctor or a nurse at the office to discuss ways to ease your anxiety.

How a Blood Culture Is Performed

The blood draw may be performed in a hospital or a specialized testing facility.

Your skin will be cleaned before the test to prevent any microorganisms on your skin from contaminating the test.

The nurse or technician will likely wrap a cuff or an elastic band around your arm to allow the veins to fill with blood and become more visible. He or she will use one needle to draw several samples of blood from your arm.

After the draw, some gauze and a bandage will be placed over the puncture site.

The culture will be performed in a laboratory.

After a Blood Culture

After the test, you will be able to go about your life as usual, provided you do not feel light-headed or faint during the test. If so, you’ll have to rest before you leave the testing facility.

Interpreting the Results

If the blood culture is positive, this means the person has a bacterial or yeast infection in the blood. An infection of this kind can be life threatening if left untreated.

Depending on the type of bacteria discovered in your blood, your doctor will perform another test called a sensitivity or susceptibility test. This helps determine which type of antibiotic will kill the bacteria.

Treatment should be started immediately either with oral antibiotics or intravenous broad-spectrum antibiotics. In the case of sepsis, the patient will be hospitalized to ensure complete treatment.

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