Capillary / Dermal Puncture (Fingerstick)

1Step-by-Step Procedure

1. 1

   Verify the order and identify the patient with two identifiers.

2. 2

   Select a puncture site: the lateral, fleshy part of the middle or ring finger in adults (avoid the thumb, index finger, and the very center of the fingertip).

3. 3

   Warm the site if circulation is poor (warm compress, 3–5 minutes) to improve blood flow.

4. 4

   Cleanse the site with alcohol and allow it to air dry completely before puncturing.

5. 5

   Hold the finger firmly and puncture perpendicular to the fingerprint ridges using a sterile, single-use lancet.

6. 6

   Wipe away the first drop of blood, which may be diluted with tissue fluid or alcohol residue.

7. 7

   Allow a rounded drop to form naturally; avoid excessive squeezing ("milking"), which dilutes the sample with tissue fluid.

8. 8

   Fill microcollection containers in the correct capillary order of draw: blood gas testing, EDTA (lavender), other additive tubes, then serum.

9. 9

   Apply gentle pressure with gauze until bleeding stops.

10. 10

    Label all containers at the bedside before leaving the patient.

What Your Instructor/Preceptor Is Checking

• ✓

  Selects an appropriate puncture site and avoids the thumb, index finger, and the exact center of the fingertip.

• ✓

  Punctures perpendicular to the fingerprint ridges, not parallel.

• ✓

  Wipes away the first drop before collecting the sample.

• ✓

  Avoids excessive milking of the finger.

• ✓

  Fills microcontainers in the correct capillary order of draw.

Common Mistakes

• ⚠

  Milking or excessively squeezing the finger, which hemolyzes the sample and dilutes it with tissue fluid.

• ⚠

  Puncturing parallel to the fingerprint ridges, which makes the blood run along the ridges instead of forming a drop.

• ⚠

  Using a site that's too cold or poorly perfused without warming it first.

• ⚠

  Puncturing the thumb, index finger, or the exact center of the fingertip (closer to bone, more painful, higher infection risk).

• ⚠

  Failing to wipe away the first drop, which can skew results with tissue fluid contamination.

Practice Tips

• →

  Warming the site for a few minutes before puncturing genuinely improves first-attempt success — don't skip it on a cold hand.

• →

  Capillary order of draw is different from venipuncture order of draw — don't default to the six-tube venous sequence.

• →

  This procedure is especially common with pediatric and geriatric patients — expect scenario-based exam questions about it.

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