
Overview
This module describes how to draw blood under sterile conditions and inoculate into a culture medium for microbiological investigations, when suspecting bacteraemia or sepsis.
Indications
Features of
sepsissepsisTypical features include tachycardia, tachypnoea, pyrexia or hypothermia, altered mental state and hypotension.
Certain localised or systemic infections that could cause bacteraemia/fungaemia such as infective endocarditis, meningitis, septic arthritis, or systemic fungal infections
Intravascular
catheter relatedcatheter relatedIn these cases, one culture should be taken from the IV cannula lumen, and the other from another site. Other than for this specific indication, blood cultures should never be drawn from an IV cannula.
bloodstream infections
In some cases to monitor the efficacy of antimicrobial treatment
Contraindications
- Damaged skin, swelling, sclerosed veins, haematomas or skin infection at the drawing site
- AV fistula or IV cannula site on the same limb
Patient information & consent
Always verify your patient’s identity and obtain informed consent before proceeding.
How do I explain this procedure?
“I need to draw blood from you to test for infections.”
What can my patient expect?
“You may feel a sharp sting when I insert the needle. This blood test may take a little longer than usual blood tests and I may need to take blood from two or three places. Afterwards, the test results can take several days.”
What is my patient’s role?
“Let me know if you have any allergies or a bleeding tendency, or use blood thinners. Fearing blood or needles is normal, but tell me if you have fainted from it. Everything must stay very clean to do this test. Keep as still as possible, and don’t cough, sneeze or reach over the equipment. Don’t touch the top of the paper I put over the area. Afterwards, press firmly on the area with cotton wool to prevent bleeding.”
Preparation
Prepare a trolley with equipment.

Documentation
- Laboratory request form
- Patient labels
- Patient notes
Equipment
Sterile gloves
Alcohol-based hand rub
- Sharps containerSharps container
If a sharps container is not within arm's length, use a kidney dish or other hard container to temporarily hold used sharps and to carry them to the sharps container for disposal.
A sterile pack (preferably a blood culture pack)
- Skin disinfectantSkin disinfectant
Commonly used preparations include 0.5-2% chlorhexidine in 70% alcohol (Steriprep), or 10% povidone iodine. There is no consensus on the superiority of one agent above another. Caution: chlorhexidine solutions may be associated with burns and skin breakdown in infants < 2 months old.
Tourniquet
Blood culture
collection bottlecollection bottleFor routine cultures, an aerobic bottle alone is sufficient, as many anaerobes will also grow in aerobic culture medium. Anaerobic bloodstream infections are uncommon. Specific anaerobic bottles, fungal culture bottles and Mycobacterial bottles may be used if these infections are suspected. Inoculate aerobic bottles first to expel residual air in the needle into an aerobic environment.
A 22 G or larger
needleneedleOne needle is used both for drawing blood and inoculating the bottle. At this point, there is not sufficient evidence to suggest using two separate needles.
A
10-20 ml syringe10-20 ml syringe20 ml if you need to draw blood for other tests as well
An alcohol swab
Cotton wool and a plaster
Laboratory specimen bag
Site & Positioning
See Venous Blood Sampling, or if no venous sites found, Arterial Blood Sampling.

Procedure
Follow medical asepsis with sterile gloves.
Perform hand hygiene.
Open the sterile pack and create a sterile field on a
cleancleanClean the table with surface disinfectant and allow it to dry.
, dry surface. Pour skin disinfectant into the well. Open the needle and syringe onto the sterile field.
Flip the lid off the blood culture bottle,
clean itclean itYou may leave the swab on top of the bottle or not, but ensure that the stopper is dry before you inoculate the bottle.
with an alcohol swab, and place it beside the sterile field.
Secure the tourniquet above the chosen puncture site.
Perform hand hygiene and don sterile gloves.
Clean the puncture site. Allow to dry.
Drape the puncture site with the
sterile sheetsterile sheetBlood culture packs contain a fenestrated drape (with a hole in the middle), but these packs are not always available. In a pinch, you can use any sterile pack and tear a hole through the sterile sheet provided.
from the sterile pack. You may touch the whole sheet.
Attach the needle to syringe and draw at least 10 ml of blood. Uphold principles of sterility.
Release the tourniquet with your non-dominant hand before withdrawing the needle. Your non-dominant hand is now non-sterile.
Use your non-sterile hand to apply gentle pressure with a dry cotton bud;
askaskDo not ask the patient to bend their arm, as this increases the risk of a haematoma.
the patient to take over.
- InoculateInoculate
Without holding the bottle, pierce the top with the needle and allow the 10 ml blood to run into it without pushing in the plunger.
the bottle. If you have other tubes to fill, fill them afterwards.
Dispose of medical waste safely.
Secure the cotton bud with a plaster if the site is still bleeding.
Rotate the bottle gently.
Label itLabel itEnsure the label does not cover the peel-off label or bar code on the bottle. Do not peel off the label and stick it in the patient's folder as it is used by the laboratory. You may stick it on the laboratory request form to aid with specimen identification.
and transport it to the laboratory in a specimen bag with the laboratory request form.
Record completion of the procedure in patient notes.
Troubleshooting
I broke sterility.
Don’t risk contamination. Dispose of everything except the blood culture bottle, and start over.
Something fell off my sterile field and I’m gloved up.
Call for an assistant to collect the equipment and open it onto your sterile field while you wait. If nobody is available, collect the equipment yourself, then put on a new pair of sterile gloves and continue.
I couldn’t get a full 10 ml of blood.
You need a full 10 ml of blood. Don’t try to take a little more from another site and put it into the same bottle. Start over completely at a new site with a new bottle.
I want to use a femoral site for blood culture.
Only as a last resort, as these sites have a higher risk for contamination than upper limb sites. Be especially meticulous about skin antisepsis when using these sites.
Also see Venous Blood Sampling and Arterial Blood Sampling.
Risks
- False positivesFalse positives
Proper skin cleansing and good aseptic technique reduce the rate of false positives, where skin commensals are cultured instead of pathogenic microbes This results in misdiagnoses and inappropriate antibiotic use.
caused by specimen contamination
- False negativesFalse negatives
To reduce the risk of false negatives, draw no less than 10 ml of blood. Take two to three separate blood cultures from different sites. The results of a single blood culture are often difficult to interpret.
caused by inadequate sampling
References
- Fabre V, Sharara SL, Salinas AB, Carroll KC, Desai S, & Cosgrove SE. Does This Patient Need Blood Cultures? A Scoping Review of Indications for Blood Cultures in Adult Nonneutropenic Inpatients. Clinical infectious diseases: an official publication of the Infectious Diseases Society of America. 2020;71(5):1339–1347.
- WHO Guidelines on Drawing Blood: Best Practices in Phlebotomy. Geneva: World Health Organization; 2010. Available from: https://www.ncbi.nlm.nih.gov/books/NBK138665/.
- Ntusi N, Aubin L, Oliver S, Whitelaw A, Mendelson M. Guideline for the optimal use of blood cultures. S Afr Med J. 2010;100(12):839-843. Published 2010 Dec 1. doi:10.7196/samj.4217