Phlebotomy Capillary Collection: Procedure, Equipment, Order of Draw & Best Practices

Capillary blood collection is a common phlebotomy technique used to obtain small blood specimens through a skin puncture, typically from a fingertip in adults or the heel in infants. It is often performed when only a small blood volume is needed, venous access is difficult, or point-of-care testing requires rapid results. Compared with venipuncture procedure, capillary collection is less invasive but requires careful technique to produce an accurate specimen.

Because capillary blood is a mixture of arterial, venous, and capillary blood along with small amounts of interstitial and intracellular fluid, improper collection can affect test results. Errors such as excessive squeezing of the puncture site, incorrect site selection, or collecting specimens in the wrong order may lead to hemolysis, tissue fluid contamination, clotting, or inaccurate laboratory values. Following standardized collection procedures helps preserve specimen quality, reduce the need for repeat collections, and support reliable clinical decision-making.

This guide explains what capillary blood collection is, when it should be used, the equipment required, approved puncture sites, the step-by-step collection procedure, the capillary order of draw, common collection errors, and best practices for obtaining high-quality specimens. The concepts covered are based on guidance from the Clinical and Laboratory Standards Institute (CLSI), the World Health Organization (WHO), the Centers for Disease Control and Prevention (CDC), and other recognized authorities, making this guide valuable for both clinical practice and certification exam preparation.

What Is Capillary Blood Collection?

Capillary blood collection, also called capillary puncture, skin puncture, or dermal puncture, is the process of collecting a small blood specimen by puncturing the skin with a sterile safety lancet. In adults and older children, the specimen is usually collected from the middle or ring finger, while in infants younger than 12 months, it is typically obtained from the medial or lateral plantar surface of the heel. This technique is commonly used when only a small blood volume is needed or when venipuncture is difficult or impractical.

Unlike venous blood obtained through venipuncture, a capillary specimen is a mixture of blood from arterioles, venules, and capillaries, along with small amounts of interstitial and intracellular fluid. Because of this mixed composition, some laboratory values may differ slightly from those obtained from venous specimens. Proper collection technique is essential to minimize tissue fluid contamination and ensure accurate test results.

Capillary collection is frequently used for point-of-care testing, bedside testing, newborn screening, and laboratory tests that require only a few drops of blood. Common examples include blood glucose monitoring, hemoglobin and hematocrit testing, bilirubin measurement in newborns, and selected blood gas or chemistry tests using microcollection devices. However, not all laboratory tests are suitable for capillary specimens, particularly those requiring larger blood volumes or tests with strict specimen requirements.

Capillary Blood vs. Venous Blood

Although both specimen types are used for laboratory testing, they differ in how they are collected, the amount of blood obtained, and their clinical applications.

Feature	Capillary Blood	Venous Blood
Collection method	Skin puncture using a sterile lancet	Venipuncture using a needle
Typical collection site	Fingertip or infant heel	Veins, usually in the antecubital area
Blood volume	Small volume	Larger volume
Blood composition	Mixture of arterial, venous, capillary blood, and small amounts of interstitial fluid	Primarily venous blood
Common uses	Point-of-care testing, newborn screening, glucose, hemoglobin, hematocrit, and other small-volume tests	Routine laboratory testing, blood cultures, coagulation studies, chemistry panels, and tests requiring larger specimens
Advantages	Less invasive, faster collection, suitable for patients with difficult venous access	Provides sufficient specimen volume and is appropriate for most laboratory tests
Limitations	Greater risk of hemolysis, clotting, and tissue fluid contamination if collected improperly	More invasive and may be challenging in patients with poor venous access

Understanding these differences helps phlebotomists choose the appropriate collection method based on the patient’s condition, the required laboratory tests, and specimen volume. Selecting the correct technique and following standardized collection procedures improves specimen quality and supports accurate laboratory results. To strengthen your understanding of venipuncture techniques, review our Routine Blood Collection Guide and test your knowledge with the Routine Blood Collection Quiz.

When Is Capillary Collection Used?

Capillary blood collection is performed when a small blood specimen is sufficient for laboratory testing or when venipuncture is unnecessary, difficult, or impractical. Although it is a valuable alternative to venous blood collection, it should only be used for tests validated for capillary specimens. The decision to collect a capillary specimen depends on the patient’s age, clinical condition, the required specimen volume, and the laboratory test being ordered.

Common Indications for Capillary Collection

Capillary collection is commonly used in the following situations:

Point-of-Care Testing

Many point-of-care (POC) tests require only a small blood sample and provide rapid results at or near the patient’s location. A fingerstick specimen is commonly used for blood glucose monitoring and other bedside tests that support immediate clinical decisions.

Pediatric and Neonatal Patients

Infants and young children often have small, fragile veins that make venipuncture more challenging. A heel puncture is the preferred method for obtaining capillary blood from infants younger than 12 months when only a small specimen is needed. This approach minimizes blood loss while providing enough blood for appropriate laboratory testing, including newborn screening and bilirubin measurement.

Difficult Venous Access

Capillary collection may be appropriate for patients whose veins are difficult to access because of dehydration, obesity, extensive scarring, burns, chemotherapy, or other medical conditions. When only a small specimen is required, a skin puncture can reduce patient discomfort and avoid repeated venipuncture attempts.

Small-Volume Laboratory Tests

Some laboratory tests require only a few drops of blood and are specifically validated for capillary specimens. Examples include:

• Blood glucose
• Hemoglobin
• Hematocrit
• Bilirubin (particularly in newborns)
• Selected point-of-care chemistry tests

The laboratory’s policies and the test manufacturer’s instructions should always be followed to ensure the requested test is approved for capillary specimens.

When Capillary Collection Should Be Avoided

Capillary collection is not appropriate for every patient or laboratory test. Venipuncture is generally preferred when a larger blood volume is required or when capillary sampling may compromise specimen quality.

Capillary collection should generally be avoided in the following situations:

• Poor peripheral circulation, which may occur in patients with shock, severe dehydration, hypothermia, or impaired blood flow, because it can reduce blood flow to the puncture site and affect specimen quality.
• Edematous puncture sites, as excess tissue fluid may dilute the specimen and produce inaccurate laboratory results.
• Areas with infection, inflammation, burns, scars, or previous punctures, which increase the risk of contamination, patient discomfort, and unreliable specimens.
• Tests requiring larger specimen volumes, such as blood cultures, coagulation studies, erythrocyte sedimentation rate (ESR), or multiple laboratory panels, because capillary collection usually cannot provide enough blood.
• Situations where the laboratory specifically requires a venous specimen to ensure accurate and validated test results.

Selecting the appropriate collection method is an important part of the pre-analytical phase. Choosing capillary collection only when clinically appropriate helps preserve specimen integrity, reduce collection errors, and improve the reliability of laboratory results. Before performing any blood collection procedure, review our Patient Preparation Guide to learn the essential steps for patient identification and preparation, then reinforce your knowledge with the Patient Preparation Quiz.

Equipment and Approved Collection Sites

Using the correct equipment and selecting an appropriate puncture site are essential for obtaining a high-quality capillary specimen. Proper supplies help reduce the risk of contamination, hemolysis, and needlestick injuries, while correct site selection promotes adequate blood flow and minimizes patient discomfort.

Required Equipment

Before beginning the procedure, gather all necessary supplies to ensure the collection can be completed safely and efficiently.

• Safety lancet: A sterile, single-use safety lancet designed for capillary puncture. The puncture depth should be appropriate for the patient’s age and the collection site.
• Microcollection tubes: Also called microtainers, these containers collect small blood volumes and may contain additives depending on the laboratory test ordered.
• Alcohol pad: Used to disinfect the puncture site before collection. The skin should be allowed to air dry completely before puncture to avoid specimen contamination and patient discomfort.
• Sterile gauze: Applied after collection to stop bleeding and protect the puncture site.
• Gloves and other personal protective equipment (PPE): Worn in accordance with Standard Precautions to reduce the risk of exposure to bloodborne pathogens.
• Specimen labels: Applied immediately after collection in the presence of the patient to ensure accurate specimen identification.
• Sharps container: An FDA-cleared, puncture-resistant container for immediate disposal of used lancets.
• Warming device (when appropriate): A warm compress or commercial warming device may be used before collection to increase capillary blood flow, particularly for heelsticks or patients with poor peripheral circulation.

Preparing all equipment before approaching the patient helps improve workflow, minimizes delays, and supports safe specimen collection.

Approved Collection Sites

Selecting the correct puncture site is critical for obtaining an adequate blood sample while avoiding injury to underlying structures.

Fingerstick Sites for Adults and Older Children

The preferred puncture sites are the palmar surface of the distal segment (fingertip) of the:

• Middle finger
• Ring finger

These fingers typically have good capillary blood flow and sufficient soft tissue, making them suitable for capillary collection. The puncture should be made slightly off-center on the fingerprint whorls rather than directly in the center of the fingertip. This location generally produces better blood flow and reduces discomfort.

Heelstick Sites for Infants

For infants younger than 12 months, the recommended puncture sites are the:

• Medial plantar surface of the heel
• Lateral plantar surface of the heel

These areas provide adequate capillary blood flow while reducing the risk of injury to the calcaneus (heel bone), nerves, cartilage, and blood vessels. Heel punctures should be performed using a safety lancet designed specifically for neonatal or infant use.

Sites to Avoid

Choosing an inappropriate puncture site can increase the risk of inaccurate test results, patient injury, or specimen rejection.

Avoid performing a capillary puncture on:

• The thumb, because it has a pulse and thicker tissue.
• The index finger, which is more sensitive and frequently used.
• The little finger, because its tissue is thinner and the bone is closer to the skin surface.
• Fingers that are swollen, bruised, scarred, calloused, infected, or previously punctured, as these conditions may affect blood flow or increase the risk of contamination.
• The center or posterior curvature of an infant’s heel, where puncturing may damage the calcaneus.
• Areas with edema, burns, inflammation, or poor circulation, which can compromise specimen quality.

Careful equipment selection and proper puncture site assessment help reduce pre-analytical errors and improve specimen integrity. Before performing the puncture, phlebotomists should confirm the patient’s identity, explain the procedure, and inspect the selected site to ensure it is safe and appropriate for collection. For a deeper understanding of infection prevention and patient safety, explore our Safety and Compliance Guide. You can also review the Anatomy and Physiology Guide to better understand the anatomical structures involved in selecting safe and effective capillary puncture sites.

Step-by-Step Capillary Collection Procedure

Following a standardized collection procedure helps obtain a high-quality specimen while minimizing patient discomfort, specimen contamination, and collection errors. Although facility policies may vary slightly, the following steps are consistent with recognized phlebotomy best practices.

1. Verify the Test Order and Prepare Supplies

Review the laboratory test request to confirm the required specimen type and determine whether capillary collection is appropriate. Gather all necessary equipment before approaching the patient, including the correct safety lancet, microcollection tubes, alcohol pads, gauze, gloves, specimen labels, and a sharps container. Having supplies ready helps prevent interruptions and reduces the risk of collection errors.

2. Identify the Patient and Explain the Procedure

Use at least two patient identifiers, such as the patient’s full name and date of birth, according to your facility’s identification policy. Compare this information with the test order before collecting the specimen.

Explain the procedure in simple terms, answer any questions, and obtain the patient’s cooperation. Proper communication can reduce anxiety and encourage the patient to keep the puncture site still during collection.

3. Perform Hand Hygiene and Put on Gloves

Clean your hands according to Standard Precautions and put on clean gloves before touching the patient or collection equipment. Gloves help protect both the patient and the healthcare worker from exposure to bloodborne pathogens but do not replace proper hand hygiene.

4. Select and Prepare the Puncture Site

Choose an approved puncture site based on the patient’s age.

• Adults and older children: Use the middle or ring finger of the non-dominant hand whenever possible.
• Infants younger than 12 months: Use the medial or lateral plantar surface of the heel.

If the site is cool or blood flow appears poor, warm it for 3 to 5 minutes using a warm compress or approved warming device. Warming increases capillary circulation and helps produce an adequate blood sample.

Clean the selected site with a 70% isopropyl alcohol pad using a circular motion from the center outward. Allow the site to air dry completely before puncturing the skin. Puncturing through wet alcohol may cause discomfort, hemolysis, or specimen contamination.

5. Perform the Skin Puncture

Remove the safety lancet from its packaging immediately before use. Position the lancet firmly against the selected site and activate it according to the manufacturer’s instructions.

For fingersticks, make the puncture across the fingerprint ridges rather than parallel to them. This promotes blood flow and prevents blood from spreading along the skin grooves, making collection easier.

After activation, immediately dispose of the used lancet in an approved sharps container without recapping or attempting to reuse it.

6. Wipe Away the First Drop of Blood

Allow a blood drop to form naturally, then wipe away the first drop with sterile gauze.

The first drop may contain residual alcohol or tissue fluid that can dilute the specimen and affect laboratory results. Removing it helps improve specimen quality before collecting the required sample.

7. Collect the Specimen

Allow additional blood drops to form naturally and collect them into the appropriate microcollection container.

Avoid excessive squeezing, milking, or scraping the puncture site. Gentle, intermittent pressure near the puncture site may be used if necessary, but excessive pressure can cause hemolysis, dilute the specimen with tissue fluid, and increase the likelihood of inaccurate laboratory results.

Hold the microcollection tube so blood flows into the container naturally. Follow the recommended capillary order of draw when collecting multiple specimens to reduce additive carryover.

Immediately after filling each additive tube, mix it by gently inverting it the number of times recommended by the manufacturer. Do not shake the tube vigorously, as this may damage blood cells and contribute to hemolysis. After collection, proper labeling, handling, and transport are equally important for maintaining specimen integrity. Learn more in our Specimen Processing Guide, then reinforce your understanding with the Specimen Processing Quiz.

8. Complete the Procedure

After collecting the required specimen, apply clean gauze to the puncture site and ask the patient to apply gentle pressure until bleeding stops. Adhesive bandages may be used when appropriate, unless contraindicated because of patient age, allergies, or facility policy.

Label all specimens immediately at the patient’s side using the required patient identifiers and any additional information required by the laboratory. Delayed or incorrect labeling is a common cause of specimen rejection and can compromise patient safety.

Inspect the specimen to ensure the required volume has been collected and that there are no visible clots when collecting blood into additive tubes. Transport the specimen according to laboratory requirements, maintaining any required temperature or time limits to preserve specimen integrity.

Finally, remove gloves, dispose of contaminated materials appropriately, perform hand hygiene, and document the procedure according to your facility’s policy.

Capillary Order of Draw

When multiple capillary specimens are collected during the same puncture, they should be filled in a specific order to minimize additive carryover and preserve specimen quality. Following the recommended capillary order of draw helps reduce the risk of inaccurate laboratory results caused by contamination between collection tubes.

The recommended capillary order of draw is:

1. Blood gas specimens (if collected)
2. EDTA microcollection tubes
3. Other additive tubes (such as heparin or fluoride-containing tubes)
4. Serum specimens (with or without a clot activator)

This order differs from the venipuncture order of draw because capillary specimens are collected directly into microcollection containers rather than evacuated tubes. Filling EDTA specimens before serum specimens helps reduce the likelihood of platelet clumping and microclot formation, which can affect hematology results. Collecting additive tubes before serum tubes also minimizes the potential for additive contamination that could interfere with laboratory testing.

In addition to following the correct order, phlebotomists should gently mix additive microcollection tubes immediately after filling by inverting them according to the manufacturer’s recommendations. Delayed or inadequate mixing may allow clot formation, making the specimen unsuitable for analysis. Vigorous shaking should be avoided because it can damage blood cells and contribute to hemolysis.

Adhering to the recommended capillary order of draw and proper mixing techniques helps maintain specimen integrity, reduce pre-analytical errors, and improve the accuracy of laboratory results. Some laboratory tests require specialized collection methods, unique specimen types, or additional handling procedures beyond routine capillary collection. To learn about these techniques, explore our Special Collections Guide and reinforce your understanding with the Special Collections Quiz.

Common Errors and Best Practices

Most capillary collection errors occur during the pre-analytical phase and are preventable through proper technique. Understanding these common mistakes helps phlebotomists collect high-quality specimens while reducing the need for repeat collections.

Common Error	Why It Happens	Best Practice
Excessive squeezing or milking	Applying too much pressure forces tissue fluid into the specimen, increasing the risk of hemolysis and dilution.	Allow blood to flow naturally and use only gentle pressure near the puncture site if needed.
Puncturing before the alcohol dries	Residual alcohol may contaminate the specimen and cause patient discomfort.	Allow the puncture site to air dry completely before using the lancet.
Choosing an incorrect puncture site	Using unsuitable fingers or the center of an infant’s heel increases the risk of injury and poor blood flow.	Use only approved finger or heel puncture sites based on the patient’s age.
Wiping away too much blood or scraping the skin	Interrupts blood flow and may contaminate the specimen.	Wipe away only the first drop, then allow subsequent drops to form naturally.
Underfilling microcollection tubes	Insufficient specimen volume or incorrect blood-to-additive ratio can affect test accuracy.	Fill each tube to the recommended volume whenever possible.
Failure to mix additive tubes promptly	Blood may clot before the additive is evenly distributed.	Gently invert additive tubes immediately after collection according to the manufacturer’s instructions.
Incorrect or delayed specimen labeling	Increases the risk of patient identification errors and specimen rejection.	Label each specimen immediately in the presence of the patient after collection.
Improper specimen handling or transport	Delays or unsuitable transport conditions may compromise specimen integrity.	Follow laboratory requirements for handling, storage, and transport.

Avoiding these errors improves specimen quality, decreases recollection rates, and supports accurate laboratory testing. Consistently following standardized procedures is one of the most effective ways to reduce pre-analytical errors and ensure reliable patient results.

Certification Exam Tips

Capillary blood collection is a frequently tested topic on certification exams such as the NHA Certified Phlebotomy Technician (CPT), ASCP Phlebotomy Technician (PBT), and AMT Registered Phlebotomy Technician (RPT). Rather than memorizing isolated facts, focus on understanding the reasoning behind each step of the collection process. Exam questions often present clinical scenarios that require applying proper collection techniques and safety practices.

Keep these key concepts in mind when studying:

• Know the approved puncture sites. For adults and older children, the preferred fingerstick sites are the middle and ring fingers. For infants younger than 12 months, use only the medial or lateral plantar surface of the heel.
• Understand when capillary collection is appropriate. It is commonly used for point-of-care testing, newborn screening, small-volume laboratory tests, and patients with difficult venous access. Venipuncture remains the preferred method when larger specimen volumes are required.
• Remember to wipe away the first drop of blood. This helps reduce contamination from tissue fluid or residual alcohol and improves specimen quality.
• Follow the correct capillary order of draw. Collect blood gases first (when required), followed by EDTA specimens, other additive tubes, and serum specimens.
• Avoid excessive squeezing of the puncture site. Excessive pressure can cause hemolysis and tissue fluid contamination, leading to inaccurate laboratory results.
• Mix additive tubes immediately after collection. Gentle inversion distributes the additive evenly and helps prevent clot formation.
• Always verify patient identity before specimen collection. Correct patient identification and specimen labeling are essential patient safety practices and are emphasized on certification exams.
• Apply Standard Precautions throughout the procedure. Perform hand hygiene, wear appropriate personal protective equipment, dispose of used lancets in a sharps container immediately after use, and follow your facility’s infection prevention policies.

A strong understanding of these principles will help you answer both knowledge-based and scenario-based exam questions while preparing you to perform safe and accurate capillary blood collection in clinical practice. Once you’re familiar with these concepts, reinforce your understanding by taking our Phlebotomy Practice Test. It includes realistic, exam-style questions covering capillary collection, patient preparation, specimen handling, safety, and other topics commonly tested on the NHA CPT, ASCP PBT, and AMT RPT certification exams.

Key Takeaways

• Capillary blood collection is a skin puncture technique used to obtain a small blood specimen, typically from the fingertip in adults and the heel in infants.
• It is commonly performed for point-of-care testing, newborn screening, small-volume laboratory tests, and patients with difficult venous access.
• Capillary blood is a mixture of arterial, venous, and capillary blood with small amounts of interstitial fluid, making proper collection technique essential for accurate results.
• The preferred fingerstick sites are the middle and ring fingers, while infants younger than 12 months should be punctured only on the medial or lateral plantar surface of the heel.
• Proper patient identification, hand hygiene, site preparation, and specimen labeling are critical steps that support patient safety and specimen quality.
• Always wipe away the first drop of blood to reduce contamination from tissue fluid or residual alcohol.
• Avoid excessive squeezing or milking of the puncture site, as it can cause hemolysis and tissue fluid contamination, leading to inaccurate laboratory results.
• Follow the recommended capillary order of draw: blood gases, EDTA specimens, other additive tubes, and serum specimens.
• Gently mix additive microcollection tubes immediately after collection to prevent clot formation and preserve specimen integrity.
• Understanding proper capillary collection techniques helps improve laboratory accuracy and prepares you for certification exams such as the NHA CPT, ASCP PBT, and AMT RPT.

Conclusion

Capillary blood collection is an important phlebotomy technique used when small blood volumes are sufficient or venous access is difficult. Obtaining a high-quality specimen depends on accurate patient identification, proper equipment selection, choosing an approved puncture site, following a standardized collection procedure, and adhering to the recommended capillary order of draw. Attention to detail throughout the collection process helps prevent common pre-analytical errors such as hemolysis, tissue fluid contamination, clotting, and specimen misidentification.

Whether you are preparing for the NHA CPT, ASCP PBT, or AMT RPT certification exam or developing your clinical skills, understanding the principles behind capillary blood collection will help you perform the procedure safely and confidently. Consistently applying evidence-based collection practices supports reliable laboratory results, improves patient safety, and contributes to high-quality healthcare.

References

1. World Health Organization. WHO Guidelines on Drawing Blood: Best Practices in Phlebotomy. Geneva: World Health Organization; 2010. Available from: https://www.ncbi.nlm.nih.gov/books/NBK138650/
2. Clinical and Laboratory Standards Institute. GP42: Collection of Capillary Blood Specimens (Current Edition). Wayne, PA: CLSI. Available from: https://clsi.org/shop/standards/gp42/
3. Centers for Disease Control and Prevention. Hand Hygiene in Healthcare Settings. Available from: https://www.cdc.gov/handhygiene/
4. The Joint Commission. National Patient Safety Goals: Improve the Accuracy of Patient Identification. Available from: https://www.jointcommission.org/standards/national-patient-safety-goals/
5. American Society for Clinical Pathology. Phlebotomy Technician (PBT) Certification. Available from: https://www.ascp.org/content/board-of-certification/get-credentialed

Finished reviewing the basics? Challenge yourself with our Phlebotomy Practice Test to apply what you’ve learned through exam-style questions with detailed explanations and identify areas that need additional review.