Does this test have other names?
Blood culture and sensitivity test, blood C&S
What is this test?
This blood test finds out if you have a systemic infection. This is an infection that
affects your whole body, not just 1 part. A sample of blood is studied in a lab to
check for bacteria or a type of fungus called yeast.
Why do I need this test?
You may need this test if you have symptoms of a systemic infection. These include:
A blood culture and sensitivity test can be done to confirm an infection, such as
pneumonia, and figure out the best way to treat it.
What other tests might I have along with this test?
If your healthcare provider believes you have pneumonia, a test called a Gram stain
may be done on a sample of sputum, which is mucus that you cough up. This helps find
out what is causing the infection.
You may also have susceptibility testing. This test finds out which antibiotic can
treat your infection. You may also have a complete blood count (CBC) either before
or with the blood culture. The CBC test shows if you have a higher level of white
blood cells, which can also be a sign of infection. Your urine may also be tested
to check for infection.
The blood culture test may need to be repeated if it comes back negative, but you
still have symptoms. It may also be repeated after you take antibiotics to make sure
the infection is gone.
What do my test results mean?
Test results may vary depending on your age, gender, health history, and other things.
Your test results may be different depending on the lab used. They may not mean you
have a problem. Ask your healthcare provider what your test results mean for you.
A positive result means bacteria or yeast are present in your blood. A negative result
means that no signs of any bacteria or yeast were found in the blood.
How is this test done?
The test is often done with at least 2 blood samples, drawn through a needle from
different veins. Taking multiple samples is more likely to produce accurate results.
The blood samples are placed in bottles with a substance that promotes growth of bacteria
or yeast. This is called a culture.
Early results may be available in 24 hours, but it can take 48 to 72 hours to find
out the specific bacteria or yeast causing your infection.
Does this test pose any risks?
Having a blood test with a needle carries some risks. These include bleeding, infection,
bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may
feel a slight sting or pain. Afterward, the site may be sore.
What might affect my test results?
Antibiotic medicine could slow the growth of the infecting bacteria. If possible,
the blood sample should be drawn just before you begin taking antibiotics.
How do I get ready for this test?
You don't need to prepare for this test. If you are taking antibiotics, let your healthcare
provider know the time of your last dose. Tell your provider about all medicines,
herbs, vitamins, and supplements you are taking. This includes medicines that don't
need a prescription and any illegal drugs you may use.