Capillary Puncture

• Capillary puncture


  • Ideal for small children when only a small volume of blood is needed
  • Advantageous in certain adult populations whose veins are inaccessible (severely burned, cancer patients, obese, geriatric patients)
  • Should not be used on patients who are extremely dehydrated or cold
• Ideal populations for capillary puncture


  • Small children
  • Severely burned
  • Cancer patients
  • Obese
  • Geriatric patients
  • Point of care testing
  • Special procedures that require capillary blood
• Equipment for capillary puncture


  • Lancet (sterile, disposable, retractable blade, for finger or heel)
  • Micro-collection containers (collect tiny amounts of blood)
  • Hematocrit tubes (manual HCT)
• Capillary puncture sites


  • Ring/Great finger
  • Infants heel (less than 1yr old)
  • Earlobe
• Capillary specimen


  Mixture of arterial, venous and capillary blood, including interstitial fluid and intracellular fluid
• Capillary blood puncture


  Higher result in glucose, lower result in total protein, calcium and potassium compared to venous blood
• Order of draw for capillary puncture


  • Gas tubes
  • Slides
  • EDTA - purple top tube
  • Heparin - light or dark green top tube
  • Other additive microcollection container
  • Serum - red top or amber tube with red top
• Procedure for capillary puncture of the finger


  1. Identify patient and verify collection orders, wear PPE

  2. Choose a finger that is not cold or edematous

  3. Clean the puncture site with alcohol and let it dry

  4. Massage the lower portion of finger to stimulate blood flow

  5. Puncture the skin while pressing the area below the puncture site, dispose puncture device

  6. Wipe away the first drop of blood with a sterile dry gauze

  7. Collect the sample in the chosen container in a downward angle and apply gentle pressure to the finger

  8. Hold gauze to the puncture site until bleeding has stopped

  9. Invert the tube according to its requirement

  10. Apply bandage to the puncture site

  11. Label the collection containers
• Area of choice for capillary puncture on babies


  • Plantar surface medial to a line drawn posteriorly from the middle of the great toe to the heel
  • Lateral to a line drawn posteriorly from between the fourth and fifth toes to the heel
• Sites to avoid for capillary puncture on babies


  • Medial or big toe side
  • Lateral or little toe slide
  • Central arch area of the foot
• Depth of puncture for capillary puncture on babies

  • Premature (0.85 mm)
  • Full-term (2 mm)
• Puncture of the fingers of infants < 1 y.o should be done only after other options are considered, as the distance to the bones and main nerves is 1.2 - 2.2 mm
• Potential issues with capillary puncture


  • Excessive crying
  • Hemolysis
  • Newborn with elevated bilirubin
  • Concentration of chemical constituents in capillary blood
  • Collecting sequential sample
• Causes of hemolysis in capillary puncture


  • Alcohol used to clean the skin was not allowed to dry
  • Finger or heel was squeezed too vigorously in an attempt to produce greater blood flow
  • Newborn infants have increased red cell fragility
• Capillary blood vs venous blood


  Glucose is higher, total protein, calcium and potassium are lower in capillary blood