Blood Specimen Collection: Cultures: Venipuncture (Ambulatory) - CE/NCPD

The content in Clinical Skills is evidence based and intended to be a guide to clinical practice. Always follow your organization’s practice.

ALERT

Draw specimens for blood cultures before giving antibiotics.

After skin antisepsis, the volume of cultured blood is the next most important variable affecting the sensitivity of detection of bacteria and fungi in the blood.^{undefined#ref1">1}

OVERVIEW

Blood culture specimens should be drawn when the patient is experiencing signs and symptoms of infection, including fever or chills, and before antibiotics are given to increase the likelihood of getting a true-positive result. If the patient has been receiving antibiotics at the time the blood cultures are drawn, the laboratory should be notified because an additive can be applied to the blood culture medium to negate the antibiotic’s effect.⁷

Consider standardized methods such as a dedicated phlebotomy team, blood culture collection kits, and diversion devices to divert a small amount of potentially contaminated blood before collecting the blood culture to reduce contamination.^2,4 Many facilities have specially trained phlebotomists who are responsible for drawing venous blood. Be familiar with the blood draw policies and procedures of your organization.⁸

Typically, at least two sets of blood cultures are ordered from different sites within a 24-hour¹ time frame. Each set contains one aerobic bottle and one anaerobic bottle (Figure 1). Orders about the spacing of the specimens may vary among practitioners and organizations.

A quantity of blood that is sufficient for isolating organisms per manufacturers’ and age-related guidelines should be drawn.⁴ A blood culture specimen set may require 20 to 30 mL¹ of blood drawn from each location.

Blood culture specimens collected using venipuncture can be drawn with either a needle and syringe or a vacuum-extraction collection device that draws blood into vacuum-sealed blood culture bottles. Avoid drawing blood cultures from a peripheral venous catheter (PIVC) on insertion or from an established PIVC or arterial line due to increased risk of contamination.⁴

Care should be taken to avoid contaminating the skin or equipment to minimize the risk of false-positive test results, which can lead to inappropriate antibiotic use, additional laboratory tests, and increased length of stay.

Suggestions for reducing blood culture contamination:²

• Proper skin antisepsis
• Blood culture bottle disinfection
• Peripheral blood culture site used (unless checking for line infection)
• Frequent hand hygiene
• Use of phlebotomy teams
• Use of diversion devices
• Education on correct blood culturing techniques
• Informed use of blood culture collection (not overusing or underusing)
• Giving feedback about contamination rates to those drawing the cultures

Draw blood for blood cultures first before collecting blood for other lab tests to maintain asepsis and prevent contamination with additives from laboratory tubes.⁴

SUPPLIES

See Supplies tab at the top of the page.

EDUCATION

• Give developmentally and culturally appropriate education based on the desire for knowledge, readiness to learn, preferred learning style, and overall neurologic and psychosocial state.
• Explain the purpose of collecting blood for cultures and the method to be used.
• Explain how a tourniquet, antiseptic swab, and venipuncture may feel.
• Explain that pressure is applied to the venipuncture site briefly after the needle is withdrawn.
• Teach the patient the signs and symptoms of recurrent bleeding (e.g., expanding hematoma at the venipuncture site) and give instructions on when to seek additional care.
• Encourage questions and answer them as they arise.

PROCEDURE

1. Determine if the patient has health literacy needs or requires tools or assistance to effectively communicate. Be sure these needs can be met without compromising safety.
2. Review the patient’s previous experience and knowledge of having blood drawn for cultures and understanding of the care to be provided.
3. Assess the patient for signs and symptoms of bacteremia, including fever and chills, before drawing blood cultures.
4. Find out whether antibiotics have been given before blood culture specimen collection and tell the practitioner and laboratory the time the antibiotic was given.

   Rationale: Resin can be added to the culture medium to negate the antibiotic effect.⁷

   If cultures are needed while the patient is receiving antibiotic therapy, get the blood culture specimen shortly before the next antibiotic dose.⁷

5. Review the manufacturer’s instructions for using a blood culture vacuum-extraction device or a syringe and needle for the collection.
6. Find out whether precautions or preconditions must be met before the collection of blood cultures. Specimen timing can be affected by medication administration, nutritional intake, procedures, or diagnostic testing.
7. Review the practitioner’s orders for the number of blood culture specimen sets to be drawn and the time required between the venipuncture for each set. Compare them with the laboratory requisitions and labels.
8. Identify the appropriate laboratory culture tubes and bottles and validate with the laboratory the sequence in which the blood specimens are to be collected (if multiple specimens are required) and the volume required for each test.⁴
9. Plan to draw out only the amount of blood needed, to avoid blood loss.
10. Gather supplies and equipment, including specimen bottles and labels and vascular visualization devices, if required, and bring them to the patient’s side. Two culture bottles (one aerobic and one anaerobic) are required for each set of blood cultures.^2,7
11. Indicate the volume of blood needed for each test on the label of each bottle. The recommended amount of blood needed for the most accurate analysis is 10 mL for each bottle.¹

    Notify the practitioner if unable to draw the required amount of blood for the blood culture sets.

12. At the patient’s side, prepare or compare laboratory requisitions and computer-generated labels (if available). Compare the labels with the patient’s self-identification by having the patient confirm the spelling of the patient’s full name and date of birth (when possible). Use computer-scanning verification, if available.

    Do not draw blood if there is a discrepancy between the laboratory requisitions or labels and the patient’s identity.

13. Prepare the blood specimen collection equipment using blood collection bottles, holders, needles, syringes, and transfer devices from the same system and manufacturer to prevent equipment incompatibility.

    Rationale: Combining different manufacturers or systems for blood specimen collection equipment may cause injury to the patient or yield incorrect test results because of hemolysis, needle disengagement, or poor tube filling. Incompatibility of components may cause failure of the process.

    Do not use pediatric culture bottles for adult blood specimens because smaller volumes diminish the yield of pathogens.

    1. If using a vacuum-extraction system, position the culture bottles securely, upright, and close enough to the venipuncture site so that the tubing and collection barrel connected to the needle reach from the selected vein to the upright culture bottle.
    2. If using a winged-butterfly or straight needle attached to a syringe, position the culture bottles securely upright and place a sterile transfer device housing a rubber-sheathed needle within reach.
    3. Clean the blood culture bottle tops and discard tubes with 70% isopropyl alcohol (i.e., alcohol pad) and let them dry completely.
14. Complete the venipuncture.
15. Transfer the blood specimen into the culture bottles.
    1. Winged-butterfly needle device method
       1. Without dislodging the needle from the patient’s vein, push the attached collection barrel briefly into the discard tube and then into the aerobic culture bottle by pushing the sheathed needle through the rubber stopper so that the vacuum pulls the blood into the bottle.⁸

          To avoid false-positive results when getting blood cultures via a venipuncture, discard a volume of blood before filling the blood culture bottles.⁴

          Watch for the rapid flow of blood into the bottle. Failure of blood to appear indicates that the vacuum is lost or the needle is not in the vein.

          Both underfilling and overfilling the cultures bottles have been linked to false-positive results and contamination.^1,3

       2. Detach the collection barrel and insert the sheathed needle through the rubber stopper of the second culture bottle.
       3. If additional blood specimens are required for other laboratory tests, insert additional blood collection tubes into the collection barrel and engage the sheathed needle, as needed.
       4. Fill the last tube and remove it from the collection barrel.
          1. If the blood is flowing sufficiently into the blood culture bottles or tubes and a tourniquet was used, release the tourniquet just before filling the last blood collection tube.
          2. If blood flow is slow, and a tourniquet was used, wait to release the tourniquet until the last bottle or tube is almost full.

       Rationale: Releasing the tourniquet before filling the last blood specimen tube reduces bleeding at the site when the needle is withdrawn.

    2. Apply a sterile 2 × 2-inch gauze pad over the venipuncture site without applying pressure. Quickly but carefully withdraw the needle from the patient’s vein, activating the safety mechanism to prevent an accidental needlestick injury.⁶

       Rationale: Applying pressure over the needle can cause discomfort and injury to the patient. Carefully removing the needle minimizes discomfort and vein trauma.

    3. Immediately apply pressure over the venipuncture site with the gauze pad until bleeding stops.
16. Needle and syringe method
    1. Apply a sterile 2 × 2-inch gauze pad over the venipuncture site without applying pressure. Quickly but carefully withdraw the needle from the patient’s vein, activating the safety mechanism to prevent an accidental needlestick injury.⁶

       Rationale: Applying pressure over the needle can cause discomfort and injury to the patient. Carefully removing the needle minimizes discomfort and vein trauma.

    2. Immediately apply pressure over the venipuncture site with the gauze pad until bleeding stops.
    3. Connect the syringe with the blood specimen to the transfer device, making sure that the syringe nozzle is not contaminated.

       Rationale: Using a transfer device with the blood collection tubes lets the vacuum to draw the blood into the tube, reducing the risk of needlestick injury.

    4. After throwing away the discard sample, distribute the blood volume between the culture bottles starting with the aerobic culture bottle.⁸

       Keep the bottles and syringe upright and make sure that no air is transferred from the syringe into the bottle.

Repeat the blood specimen collection sequence for a second set. Blood culture sets are usually drawn in immediate succession.

Rationale: Unless ordered by the practitioner or per the organization’s practice, blood should be collected with at least two different blood draws from two different peripheral sites.^1,4

Gently mix the culture broth and blood in the culture bottles.

Rationale: Mixing gently blends the medium and the blood.

Label the specimens in the presence of the patient.⁵

Place the labeled specimens in a biohazard bag and transport it to the laboratory.

Assist the patient to a comfortable reclining position for several minutes. ⁸

EXPECTED OUTCOMES

• Venipuncture is successful without nerve or adjacent tissue injury.
• Aseptic technique is maintained.
• Venipuncture site shows no evidence of continued bleeding or hematoma after blood specimen collection.
• Patient tolerates procedure with minimal anxiety, fear, or discomfort.
• All required laboratory blood specimens are collected, and accurate results are received.

UNEXPECTED OUTCOMES

• Nerve or adjacent tissue injury occurs.
• Aseptic technique is not maintained.
• Hematoma forms at venipuncture site.
• Infection or phlebitis develops at venipuncture site.
• Patient has vasovagal response, including dizziness, fainting, or loss of consciousness.
• Hemostasis is not achieved.
• Blood culture has a false-positive result.
• Blood culture specimen is not enough for testing and cannot be processed.
• Needlestick injury happens.

DOCUMENTATION

• Date and time of venipuncture and number and location of attempts
• Location and description of venipuncture site
• Volume of blood drawn and collected in each bottle
• Name and credentials of person doing venipuncture
• Disposition of specimens
• Inability to get blood cultures, if unsuccessful
• Education
• Patient’s tolerance of venipuncture
• Unexpected outcomes and related interventions

PEDIATRIC CONSIDERATIONS

• Use appropriate-size vacuum bottles or tubes and vacuum strength. Large tubes with full vacuum may exert too much pressure on a pediatric patient’s vein.⁷
• Carefully assess a pediatric patient who is at risk for venous collapse from the vacuum-extraction system.
  • A young child may not be able to withstand vacuum system pressure or may require a smaller tube.
  • Pressure from larger tubes may cause vein wall damage, leading to infiltration.
• Follow the organization’s practice for use of chlorhexidine gluconate on neonates.
• Consider that minimum and ideal volumes for blood culture specimens for a neonate and child vary based on weight.

OLDER ADULT CONSIDERATIONS

• The appropriate-size vacuum bottles or tubes and appropriate vacuum strength should be used.
  • Large tubes with full vacuum may exert too much pressure on an older adult’s vein.
  • An older adult may not be able to withstand vacuum-system pressure or may require a smaller tube.
  • Pressure from larger tubes may cause vein wall damage, leading to infiltration.

REFERENCES

1. Centers for Disease Control and Prevention (CDC). (2024). Preventing adult blood culture contamination: A quality tool for clinical laboratory professionals. Retrieved August 13, 2025, from https://www.cdc.gov/lab-quality/docs/bcc-prevention_a-quality-tool_cdc.pdf
2. Centers for Disease Control and Prevention (CDC). (2025). Blood culture contamination: An overview for infection control and antibiotic stewardship programs working with the clinical laboratory. Retrieved August 13, 2025, from https://www.cdc.gov/lab-quality/media/pdfs/2024/08/fs-bloodculture-508.pdf
3. Doern, G.V. and others. (2020). A comprehensive update on the problem of blood culture contamination and a discussion of methods for addressing the problem. Clinical Microbiology Reviews, 33(1), e00009-e00019. doi:10.1128/CMR.00009-19 Retrieved August 13, 2025, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6822992/pdf/CMR.00009-19.pdf
4. Infusion Nurses Society (INS). (2024). Infusion therapy standards of practice. Standard 41: Blood sampling. Journal of Infusion Nursing, 47(Suppl. 1), S140-S146.
5. Joint Commission, The. (2025). National Patient Safety Goals for the hospital program. Retrieved August 13, 2025, from https://digitalassets.jointcommission.org/api/public/content/9be383450fc941df806b76c5fbdd9ae6?v=3c600c3a
6. Occupational Safety and Health Administration (OSHA). (n.d.). Patient care unit: Needlestick/sharps injuries. Retrieved August 7, 2025, from https://www.osha.gov/etools/hospitals/patient-care-unit/needlestick-sharps-injuries
7. Pagana, K.D., Pagana, T.J., Pagana, T.N. (2025). Chapter B: Blood culture and sensitivity. In Mosby’s diagnostic and laboratory test reference (17th ed., pp. 106-156). St. Louis: Elsevier.
8. Perry, A.G. (2025). Chapter 7: Specimen collection. In A.G. Perry and others (Eds.), Clinical nursing skills & techniques (11th ed., pp. 178-226). St. Louis: Elsevier.

Clinical Review: Genevieve L. Hackney, MSN, RN

Published: October 2025