Understanding Your Medical Test: What It Is, Why It Is Done, and What Your Results Mean
A blood culture test detects harmful bacteria in your bloodstream to help diagnose infections.
{"A blood culture test checks if bacteria are growing in your blood","It helps doctors diagnose serious infections like sepsis","The test involves taking a small blood sample and placing it in a special container to see if bacteria grow","Results usually take 2-5 days to confirm if bacteria are present","If bacteria are found, doctors can determine the best antibiotic treatment"}
Key facts at a glance
- LOINC
- 17930-9
- Short code
- BCID3
- Synonyms
- Bacteria Bld Aerobe Cult org #3
- Category
- chemistry
- Sample
- whole-blood
- Container
- Aerobic blood culture bottle (e.g., BacT/ALERT FA Plus or BACTEC Plus Aerobic/F) paired with an anaerobic bottle per standard blood culture set
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- aerobic-culture
- CPT
- 87040
- SNOMED
- 104182005
- Specimen volume
- 8-10 mL per aerobic bottle for adults; 1-4 mL for pediatric bottles based on patient weight and age
- Stability
- Specimens should be transported to the laboratory within 2 hours of collection and incubated immediately. If transport is delayed, bottles can be held at room temperature (20-25°C) for no more than 12-16 hours without compromising results.
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 48–120 hours
- Order
- routine
What exactly is this test, what does it measure or look for in my body, and how can the results help my doctor care for me?
A blood culture test is a laboratory test that checks for bacteria or other germs in your blood. When bacteria enter your bloodstream, it can cause a serious infection called bacteremia or sepsis. This test helps doctors find out if you have such an infection and identify which specific bacteria are causing it.
How is this test performed, how should I prepare for it, and what can I expect to happen during the procedure itself?
A healthcare provider will clean the skin on your arm with an antiseptic to prevent contamination. Then, they will draw a small amount of blood, usually from a vein in your arm. The blood sample is placed in special bottles containing nutrients that help bacteria grow if they are present. These bottles are then placed in an incubator at the laboratory for several days.
Why might I need this test, what symptoms or health concerns could make my doctor recommend it, and who is most likely to benefit from it?
Your doctor may order a blood culture test if you have symptoms of a serious infection, such as fever, chills, rapid breathing, confusion, or low blood pressure. It is commonly used to diagnose sepsis, endocarditis (heart valve infection), or other bloodstream infections. The test is also used to monitor patients during treatment for infections.
What do the results of this test mean, how are normal and abnormal results different, and when and how will my doctor share them with me?
A negative result means no bacteria were found in your blood sample, which suggests you do not have a bloodstream infection. A positive result means bacteria were detected, and the laboratory will identify the specific type. This information helps your doctor choose the most effective antibiotic treatment. Sometimes, the test may be repeated to confirm the results or to check if treatment is working.
Reference range
No growth of pathogenic bacteria after standard incubation period (typically 5 days). Positive results are reported with organism identification and antibiotic susceptibility testing when indicated.N/A
Strict aseptic technique is required during venipuncture to prevent contamination. Skin should be disinfected with chlorhexidine or 70% isopropyl alcohol. Collection is preferably performed before initiation of antimicrobial therapy. Multiple sets from different venipuncture sites are recommended to distinguish true bacteremia from contamination.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Blood culture testing is essential for diagnosing bacteremia (bacteria in the blood) and sepsis, which are life-threatening conditions. Early detection through blood cultures allows doctors to start targeted antibiotic therapy, improving patient outcomes. The test also helps identify the specific bacteria causing the infection, enabling more precise treatment and helping to combat antibiotic resistance. Additionally, blood culture results guide doctors in determining how long antibiotic treatment should continue.
Frequently asked questions
Is the blood culture test painful?
How long does it take to get results?
Do I need to prepare for the test?
What happens if my blood culture is positive?
Can a blood culture be false positive?
Sources
- 1
- 2
- 3
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy