Phlebotomy — 12 Scored Items
8% of the exam
Phlebotomy is 12 of the 150 scored items — 8% of the exam, and the most rule-driven domain on the whole test plan (knowledge statements k122–k146). Almost every item has one defensible answer, fixed by CLSI, OSHA, or The Joint Commission, so memorized sequences pay off directly here in a way they don't elsewhere. Six cycles below: identification and labeling, site selection, technique, the order of draw, capillary puncture, then complications and specimen integrity. Answer each check out loud before you reveal it — looking at the answer first feels productive and teaches you nothing.
Identify, verify, label — the rules with no exceptions
Three steps happen before the needle. First, identify: The Joint Commission (NPSG.01.01.01) requires at least two patient identifiers — full legal name and date of birth are the standard pair. A room number or physical location is never an identifier. Have the patient state and spell their name; do not ask "Are you Mr. Garcia?" Second, verify the requisition: test ordered, date, time, ordering provider, diagnostic code, dietary restriction. Identifiers must match across requisition, patient, and label. Third, label at the patient's side, at the time of collection, before you leave the room — never in advance. Fasting means nothing by mouth except water, typically 8 to 12 hours. Confirm it, and document it if the patient did not fast.
Reading the antecubital fossa — first choice, last resort, never
CLSI ranks antecubital veins by position, not by name: median (center) first, lateral/cephalic (thumb side) second, medial/basilic (little-finger side) last. The median cubital is first choice because it is well anchored in surrounding tissue, usually the largest and straightest, and least likely to roll. The basilic is last resort — the brachial artery, the median nerve, and the medial antebrachial cutaneous nerve all lie close beneath it. Never use the underside or the sides of the wrist. Avoid entirely: the arm on a mastectomy side, an arm with an AV fistula or graft, edema, extensive burns or scarring, an active hematoma, and any site above an IV. Adult foot and leg draws require provider approval.
Tourniquet, needle, and the three delivery systems
Apply the tourniquet 3 to 4 inches (7.5–10 cm) above the site, for no more than one minute (CLSI). Past 60 seconds, hemoconcentration falsely raises potassium, total protein, and cell counts; if the search runs long, release and let the arm equilibrate at least two minutes before reapplying. Release as soon as blood flows, and always before withdrawing the needle. The patient may clench once — never pump the fist, which releases potassium from muscle. Cleanse with 70% isopropyl alcohol using friction, working outward in concentric circles, and let it air dry completely; wet alcohol stings and hemolyzes. Do not re-palpate after cleansing. Anchor the skin with your thumb below the site; insert bevel up at 30 degrees or less (typically 15 to 30). Evacuated tube is the preferred closed system; syringe suits fragile veins; butterfly suits hand and pediatric veins. With a butterfly, if a light blue citrate tube is the first tube drawn, fill a discard tube first — the air sitting in the tubing would otherwise underfill it and break the 9:1 ratio.
The order of draw — one sequence, six positions
The reason an order exists is carryover: additive clinging to the needle contaminates the next tube. CLSI order (GP41, renumbered PRE02 for the 8th edition; the sequence did not change): blood cultures first for sterility, then light blue sodium citrate (coagulation), then red or gold serum (chemistry, serology), then green heparin (STAT chemistry), then lavender or pink EDTA (CBC, blood bank), then gray sodium fluoride/potassium oxalate (glucose, lactate, alcohol). The classic failure is EDTA carryover: EDTA chelates calcium and its salt is potassium-based, so a contaminated chemistry tube reads falsely low calcium and falsely high potassium. Invert additive tubes gently right after filling — light blue 3 to 4 times, red or gold with clot activator or gel 5, green, lavender, and gray 8 to 10. A plain glass red tube with no additive needs none. Never shake.
Capillary and dermal puncture
Capillary blood mixes arterial, venous, and interstitial fluid, so values differ from venous: glucose runs higher; potassium, calcium, and total protein run lower. The capillary order of draw is reversed — blood gas first, then EDTA, then other additives, serum last — because skin puncture activates platelets instantly and a clotted CBC is worthless. Sites (CLSI GP42): over one year of age, the palmar surface of the distal third or fourth finger, off-center and perpendicular to the fingerprint. Never the thumb, index finger, or fifth finger, and never an earlobe. Under one year, use the heel — only the medial or lateral plantar surface, never the posterior curvature or the arch. Maximum heel puncture depth is 2.0 mm in a full-term infant; use a device manufactured for that depth and for the infant's size. Wipe away the first drop, and never squeeze or milk the site.
Complications and specimen integrity
Hemolysis is the top preventable error. Causes: a needle bore finer than 23 gauge (a 25-gauge draw is the classic offender), drawing through a vascular access device, a hard syringe pull, wet alcohol, shaking tubes, a tourniquet left on past one minute, and under- or overfilled tubes. It falsely raises potassium, magnesium, phosphorus, and LDH. Respond to complications immediately. Electric, radiating pain means possible nerve contact — remove the needle at once, apply pressure, report to the provider, and document. Swelling during the draw is a hematoma — release the tourniquet, withdraw, hold firm pressure. Pale, sweaty, lightheaded is syncope — remove the needle, lower the head, stay with the patient, no ammonia inhalants. Repeated draws cause iatrogenic anemia; use microcollection volumes. Stop after two unsuccessful attempts and hand off. Afterward: pressure at least two minutes, arm straight, elbow not bent; if it is still bleeding, two more minutes, then three more, and get help if bleeding continues past roughly eight minutes total.
Where people lose points
✗ Venous order of draw vs capillary order of draw
✓ Venous: cultures, light blue, red/gold, green, lavender EDTA (fifth), gray. Capillary: blood gas, EDTA (near-first), other additives, serum LAST. EDTA moves to the front in capillary collection because skin puncture activates platelets immediately. Apply the venous order to a heel stick and you hand the lab a clotted CBC.
✗ A short-draw light blue tube vs a short-draw red tube
✓ A plain red serum tube has no additive ratio to protect, so a partial fill is often still testable. A light blue citrate tube must hold 9 parts blood to 1 part 3.2% sodium citrate. Underfilled, the excess citrate binds extra calcium and falsely PROLONGS PT, aPTT, and INR — which can look like a coagulopathy in a normal patient. Labs reject fills below roughly 90%. This is also why a butterfly draw needs a discard tube ahead of a first-position light blue: the air in the tubing steals that fill volume.
✗ Hemolysis vs hemoconcentration
✓ Both can raise potassium, but the mechanism and the fix differ. Hemolysis = red cells physically ruptured (needle bore finer than 23 gauge, wet alcohol, shaking, forceful syringe pull); the plasma looks pink-red and the specimen is rejected. Hemoconcentration = plasma water pushed out of the vessel by a tourniquet left on past one minute; the specimen looks perfectly normal but protein, potassium, and cell counts all read high.
✗ Blood culture bottle order with a butterfly vs with a syringe
✓ Butterfly (winged set): AEROBIC bottle first, so the air already sitting in the tubing is flushed into the bottle that tolerates oxygen. Syringe: ANAEROBIC bottle first, because a syringe holds no air and the anaerobes get the least oxygen exposure. Either way, blood cultures come first in the overall order of draw, before every other tube. Your facility's protocol and the bottle manufacturer's instructions govern the actual sequence — follow them.
✗ Clenching the fist vs pumping the fist
✓ A single gentle clench to help you locate the vein is acceptable. Repeated pumping is not — the forearm muscles release potassium into the local blood, producing pseudohyperkalemia that can look like a critical value and trigger an unnecessary workup. If a patient starts pumping on their own, stop them.
✗ 70% isopropyl alcohol vs chlorhexidine skin prep
✓ Routine venipuncture: 70% isopropyl alcohol with friction, then FULL air dry. Blood cultures: a chlorhexidine-alcohol skin antiseptic (commonly 2% chlorhexidine gluconate in 70% isopropyl alcohol), applied with friction and allowed to dry completely per the product's instructions — the dry time IS the antisepsis, not a formality. Never re-palpate a prepped site with an unclean finger; if you must, re-prep. For legal blood alcohol collection, facility protocol typically requires a non-alcohol antiseptic.
✗ Ordinary needle pain vs nerve contact
✓ Ordinary venipuncture pain is a brief, localized sting that fades. Nerve contact is immediate, electric or shooting, and RADIATES up or down the arm, often with numbness or tingling. Ordinary pain: continue. Nerve pain: remove the needle immediately, do not reposition and probe, apply pressure, notify the provider, and document. This is the single most litigated phlebotomy complication.
✗ Reporting an out-of-range result vs interpreting it
✓ A CCMA may recognize that a value is out of range, flag it, route it to the ordering provider, and document the notification — that is literally a task statement (3E13). A CCMA may NOT tell the patient what the value means, what caused it, or what to do about it. "Your potassium is high, cut back on bananas" is practicing outside your scope of practice. Correct script: "The provider will review this and contact you."
✗ Pre-labeling tubes vs labeling at the patient's side
✓ Pre-labeling at the workstation feels efficient and is a direct cause of wrong-patient specimens. TJC requires the container to be labeled in the presence of the patient at the time of collection. Also wrong: carrying labeled empty tubes between rooms, and labeling after you have left. If you cannot attest the label went on at that patient's side, the specimen is recollected.
✗ Emptying a syringe with a needle vs with a transfer device
✓ Never push blood through a needle into a tube stopper — that is a needlestick waiting to happen, and OSHA (29 CFR 1910.1030) requires engineering controls that eliminate the exposure. Use a blood transfer device and let the tube's own vacuum pull. Forcing the plunger also hemolyzes the sample. Same standard: never recap a contaminated needle, activate the safety device immediately, and discard at the point of use.
Numbers to memorize
| Minimum patient identifiers | At least 2 — full legal name + date of birth (TJC NPSG.01.01.01). Room number/location never counts. |
| When and where the tube is labeled | At the patient's side, at the time of collection, before leaving the room |
| Tourniquet placement | 3–4 inches (7.5–10 cm) above the intended puncture site |
| Maximum tourniquet time | 1 minute (CLSI). If exceeded: release and let the arm equilibrate at least 2 minutes before reapplying. |
| Needle insertion angle | 30 degrees or less (typically 15–30), bevel up |
| Gauge — routine venipuncture | 21 gauge (22 gauge is also routinely used) |
| Gauge — butterfly / small, fragile veins | 23 gauge |
| Gauge — blood donation / therapeutic phlebotomy | 16–18 gauge |
| Gauge threshold for hemolysis risk | Finer than 23 gauge — a 25-gauge draw is the classic cause (higher number = finer bore = more shear on red cells). 23 gauge itself is acceptable and standard for butterfly draws. |
| Order of draw — venous (CLSI GP41 / PRE02) | 1 Cultures → 2 Light blue citrate → 3 Red/gold serum → 4 Green heparin → 5 Lavender/pink EDTA → 6 Gray fluoride/oxalate |
| Yellow tubes — two different tubes | Yellow SPS = a blood culture tube, drawn FIRST. Yellow ACD (HLA, paternity, DNA) is drawn AFTER the gray tube. |
| Order of draw — capillary (CLSI GP42) | Blood gas → EDTA → other additive tubes → serum last |
| Light blue tube ratio | 9 parts blood : 1 part 3.2% sodium citrate. Reject below roughly 90% fill. |
| Discard tube with a butterfly | Required when a light blue citrate tube is the FIRST tube drawn through a winged set — it clears the air in the tubing dead space so the citrate tube fills completely |
| Inversions — light blue citrate | 3–4 |
| Inversions — red/gold with clot activator or gel (SST) | 5 |
| Inversions — plain glass red, no additive | 0 |
| Inversions — green, lavender/pink, gray | 8–10 (gentle 180° turn and back; never shake) |
| Blood culture bottle order — butterfly | Aerobic first (air in the tubing goes to the aerobic bottle) — confirm against facility protocol and the bottle manufacturer's instructions |
| Blood culture bottle order — syringe | Anaerobic first (no air in the syringe) — confirm against facility protocol and the bottle manufacturer's instructions |
| Blood culture skin antisepsis | Chlorhexidine-alcohol antiseptic (commonly 2% chlorhexidine gluconate in 70% isopropyl alcohol); apply with friction and let dry completely per the product's instructions; do not re-palpate |
| Finger stick site (over 1 year) | Palmar surface, distal 3rd or 4th finger, off-center, perpendicular to the fingerprint. Never the thumb, index, or 5th finger; never an earlobe. |
| Heel stick site (under 1 year) | Medial or lateral plantar surface only — never the posterior curvature or the arch |
| Maximum heel puncture depth | 2.0 mm in a full-term infant (CLSI GP42) — use a device manufactured to that depth and sized for the infant |
| First drop of capillary blood | Wipe away — it is contaminated with tissue fluid |
| Fasting specimen | Nothing by mouth except water, typically 8–12 hours |
| Maximum venipuncture attempts | 2 (standard facility policy), then hand off to another qualified person |
| Post-draw pressure | At least 2 minutes, arm straight, elbow not bent (CLSI). Still bleeding: 2 more minutes, then 3 more; get help past roughly 8 minutes total. Leave the bandage on at least 15 minutes. |
| Serum/plasma separation from cells | Centrifuge and separate within 2 hours of collection (CLSI). Let serum tubes clot completely first, per the tube manufacturer's instructions. |
| Transported chilled (ice slurry) | Ammonia, lactate, blood gases |
| Transported light-protected | Bilirubin |
| Transported at 37 °C | Cold agglutinins |
| Hemolysis falsely raises | Potassium, magnesium, phosphorus, LDH |
| Hemoconcentration falsely raises | Potassium, total protein, cell counts |
| EDTA carryover into a chemistry tube | Calcium falsely LOW, potassium falsely HIGH |
| Sharps handling (OSHA 29 CFR 1910.1030) | Never recap a contaminated needle; activate the safety device immediately; discard in a sharps container at the point of use |
Test yourself
No answers here on purpose — retrieving them is the practice. Drill this domain if any of these stall you.
- Name the six positions of the venous order of draw in sequence, with the additive in each and one test each is used for.
- State the required number of inversions for a light blue tube, a gel serum tube, a lavender tube, and a plain glass red tube with no additive.
- Why is the median cubital the first-choice vein, and which artery and which two nerves lie close beneath the basilic and make it the last resort?
- A patient has an IV running in one arm and a mastectomy on the opposite side. Walk through your decision, including whom you consult and what you may not decide alone.
- How long may a tourniquet stay on, what three measurements are falsely elevated past that limit, and what do you do if you exceed it?
- List seven causes of hemolysis and the four analytes it falsely raises.
- Give the capillary order of draw and explain in one sentence why it is not the venous order.
- On an infant's heel, where may you puncture, where may you not, and what is the maximum depth for a full-term infant?
- Mid-draw a patient reports electric pain radiating to the hand. State your next four actions, in order.
- Explain mechanically why an underfilled light blue tube produces a falsely prolonged INR, at what fill level the lab rejects it, and when a butterfly draw needs a discard tube.
- Which blood culture bottle is filled first with a butterfly, which with a syringe, what is the reason for each, and what ultimately governs the sequence?
- Name eight reasons a laboratory rejects a specimen, and state what happens to a mislabeled tube.
- A patient asks what their high glucose result means. State exactly what you may say and what you may not say, and name the boundary you are respecting.
- Name the two acceptable patient identifiers, one that is never acceptable, and the exact moment and place the tube is labeled.
- Which specimens travel chilled, which travel light-protected, which travel at 37 °C, and within how long must serum be separated from cells?
- Distinguish hemolysis from hemoconcentration: mechanism, appearance of the specimen, and how each is prevented.