Capillary Puncture and the Capillary Order of Draw
Updated October 27, 2026
A capillary puncture (fingerstick or heel stick) collects a small amount of blood from the capillary beds. It’s used for infants, for patients with fragile or hard-to-find veins, and for point-of-care tests such as glucose. The NHA CPT exam expects you to know the sites, the technique and a different order of draw from venipuncture. Here’s what to know, followed by free practice questions.
Always follow your facility’s procedure and the device manufacturer’s instructions.
Sites
- Adults and older children: the fleshy pad of the middle or ring finger of the non-dominant hand, slightly off center, across the fingerprint lines.
- Infants: the medial or lateral plantar surface of the heel (the outer edges of the bottom of the heel). Avoid the center and back of the heel, where the bone is close to the surface.
Avoid the thumb and index finger, which are more sensitive and have thicker skin, and the pinky, where the bone is close to the surface. Never puncture a site that is swollen, bruised, scarred or infected.
Technique basics
- Warm the site if needed, to increase blood flow.
- Clean the site with alcohol and let it dry completely. Wet alcohol can hemolyze the sample and sting.
- Puncture with a lancet designed for the site and patient size.
- Wipe away the first drop of blood, which contains tissue fluid.
- Collect the drops without hard squeezing (“milking”), which adds tissue fluid and can hemolyze the sample.
Capillary order of draw
The order is different from venipuncture, because clotting starts as soon as the skin is punctured:
- Blood gases (if collected by capillary)
- EDTA (lavender) tubes
- Other additive tubes (such as heparin)
- Serum tubes (no additive)
EDTA comes first so platelets don’t clump before the sample reaches the tube.
Free practice questions
-
Where should a heel stick be performed on an infant?Answer: CThe medial and lateral plantar surfaces of the heel have enough tissue over the bone. The center and back of the heel risk puncturing the bone.
-
Why is the first drop of blood wiped away during a capillary puncture?Answer: AThe first drop is mixed with tissue fluid, which can affect results, so it's wiped away with clean gauze.
-
In the capillary order of draw, which tube is filled before serum tubes?Answer: BFor capillary collection, EDTA is collected early so platelets don't clump before the sample is mixed with the anticoagulant. Serum tubes come last.
-
Which finger is usually preferred for a fingerstick?Answer: DThe middle and ring fingers have enough tissue and are less sensitive. The thumb and index finger are more sensitive, and the pinky has the bone close to the surface.
-
Why should the alcohol be allowed to dry before a capillary puncture?Answer: AResidual alcohol can hemolyze red cells and affect results, and it stings. Let the site air-dry completely.
-
Why should a phlebotomist avoid hard squeezing (milking) the finger?Answer: BSqueezing hard pushes tissue fluid into the sample and can damage red cells, both of which can change test results.
Pass your phlebotomy exam on the first try
- All 173 questions on safety, patient preparation, routine and special collections and processing
- An explanation for every answer, with the CLSI standard, OSHA rule or guideline behind it
- Unlimited full 100-question practice exams, with each domain in its real share