Skip to content

Gram Stain Bacteria Identification (Blood Culture Screening)

Published: August 9, 2026Updated: August 16, 2026

This test helps detect the presence of bacteria in your blood, often used as an initial screening step before confirming infection through blood cultures.

Quick summary

["Early detection of blood infections may help guide treatment decisions."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
75688-2
Short code
Deprecated GN bact Bld Pos Prb Mag-Imp
Synonyms
Deprecated GN bact Bld Pos Prb Mag-Imp
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
probe-mag-capture
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

What Is This Test For?

This test involves examining a sample of your blood under a microscope to look for bacteria. It’s typically performed as part of a broader blood culture process to identify potential infections, such as sepsis or bloodstream infections.

How Is the Sample Collected?

A small amount of blood is drawn from a vein, usually in your arm, and sent to the lab. The sample is then processed to identify any bacteria present.

When Might You Need This Test?

You may need this test if you have symptoms like fever, chills, or signs of infection, especially if you’re at higher risk (e.g., undergoing surgery, having a weak immune system, or receiving medical devices like catheters).

What Does a Positive Result Mean?

A positive result suggests the presence of bacteria in your blood, which may indicate an infection. Further testing, such as blood cultures, is usually needed to confirm the type of bacteria and guide treatment.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Blood Culture Gram Stain Screening

Frequently asked questions

Why was I asked to take this test?
Your healthcare provider may recommend this test if you have symptoms of infection, a weakened immune system, or are receiving treatments that increase your risk of blood infections.
What happens if my test results are abnormal?
If bacteria are found, your doctor will likely order additional tests (like blood cultures) to determine the exact cause and recommend the best treatment, such as antibiotics.
How long does it take to get results?
Results from this screening test are typically available within a few hours to a day, but confirmatory blood cultures may take longer (up to several days).
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

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