Phlebotomy · Study drill
Order of draw trainer
Put the blood collection tubes in the right order, learn what each additive does, and match common lab work to the right tube. Free, with every answer explained.
- Tube order drill
- Test-to-tube practice
- Every answer explained
- No sign-up needed
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Part 1 · The chart
The venipuncture order of draw
The order below is the one CLSI GP41 is commonly summarized as, and the one the university lab manuals in the sources use. It exists for one reason: the additive in one tube can be carried into the next tube and change its result.
- 1Blood cultureVaries by bottle set
- 2CitrateLight blue
- 3SerumRed / Gold
- 4HeparinDark green / Light green
- 5EDTALavender / Pink
- 6FluorideGray
- 1
Blood culture bottles
Common cap color: Varies by bottle set
- Additive
- Culture broth in a sterile bottle or tube
- What it does
- Keeps any microorganisms in the sample alive so the lab can grow and identify them.
- Why here
- Drawn first so the culture stays sterile and no other tube’s additive can reach it.
- Common uses
- Blood cultures
- 2
Sodium citrate
Common cap color: Light blue
- Additive
- Sodium citrate solution (3.2% at the labs in the sources)
- What it does
- Binds calcium so the sample cannot clot. The plasma is used for clotting studies.
- Why here
- Comes right after the culture bottles so nothing can be carried into it: EDTA from a later tube, for example, can lengthen clotting times.
- Note
- Fill it to the line. The tube is built for a 9:1 blood-to-additive ratio, and a short draw can lengthen clotting times. With a winged (butterfly) set and the citrate tube first, draw a discard tube to fill the tubing’s dead space; it does not need to be full.
- Common uses
- PT/INR, aPTT and other clotting studies
- 3
Serum tubes
Common cap colors: Red / Gold
- Additive
- None, or a clot activator, with or without a gel separator
- What it does
- The blood is allowed to clot. Spinning separates the serum, and a gel barrier (when there is one) holds it above the cells.
- Why here
- Goes after citrate because the clot activator in a plastic serum tube can upset clotting studies if it is carried into the citrate tube. Only a culture bottle, a plain glass tube or a plastic tube with no clot activator may come before citrate.
- Common uses
- Chemistry panels, serology, drug levels and other serum work
- 4
Heparin
Common cap colors: Dark green / Light green
- Additive
- Sodium heparin or lithium heparin, with or without a gel separator
- What it does
- Works through antithrombin to switch off clotting factors, mainly thrombin and factor Xa, so the sample stays liquid and gives plasma.
- Why here
- Drawn before EDTA so EDTA cannot reach it: EDTA carried into a chemistry tube can falsely raise potassium and lower calcium readings.
- Note
- Use the heparin salt the lab names for the work. A lithium level, for example, can never go in lithium heparin; the WHO table lists sodium heparin for it.
- Common uses
- Plasma chemistry
- 5
EDTA
Common cap colors: Lavender / Pink
- Additive
- EDTA
- What it does
- Binds calcium so the sample cannot clot. The whole blood is kept for cell counts and blood bank work.
- Why here
- Sits near the end because its carryover does the most damage: EDTA in a chemistry tube can read as high potassium and low calcium, and in a citrate tube it can lengthen clotting times.
- Note
- Needs a full draw. Mix by gentle inversion; never shake.
- Common uses
- CBC and other hematology, hemoglobin A1c; pink for blood bank
- 6
Sodium fluoride
Common cap color: Gray
- Additive
- Sodium fluoride with potassium oxalate
- What it does
- Fluoride slows glycolysis, which preserves the glucose in the sample; potassium oxalate is the anticoagulant.
- Why here
- Drawn last in the standard order, so its fluoride and oxalate cannot be carried into any other tube.
- Note
- Needs a full draw; the WHO guideline notes that a short draw may cause hemolysis.
- Common uses
- Glucose when processing is delayed, and lactate (kept on ice)
- Mix every additive tube by gentle inversion, the number of times your lab specifies. Never shake a tube.
- Cap colors are common conventions. They can differ by manufacturer and by lab, and so can the exact order for tubes not listed here, so your lab’s procedure manual always comes first.
- For study only. This is a learning aid, not a collection procedure.
Part 2 · The drill
Tap the tubes in order
The six tube groups come up shuffled. Tap them in the order you would draw them. The clock runs until the last tube is placed, every tap gets feedback, and each mistake is explained at the end.
Part 3 · Practice questions
Which tube, and why
Ten questions that mix the common pairings (CBC, PT/INR, A1c, lactate, blood cultures) with the additive facts behind them. One at a time, with the answer explained before you move on. Your result is free.
The bonus
The badge card, the capillary order and 20 more questions
Locked until you unlock the bonus above
- A badge-size order-of-draw card to print: the venipuncture order on one panel, the skin-puncture order on the other.
- 20 more tube and additive questions, every answer explained.
- The skin-puncture (capillary) order side by side with the venipuncture order, and why it is almost the reverse.
Sources
Where these facts come from
Everything on this page is written in our own words from these public sources. Where they differ on a detail, your lab’s procedure manual decides.
- WHO Guidelines on Drawing Blood: Best Practices in Phlebotomy (2010) · Table 2.3 (order of draw, additives and what they do) and section 7.1.3 (skin-puncture order).
- CLSI, Order of Blood Draw Tubes and Additives · The GP41 order of draw, example cap colors, and which tubes may come before a coagulation tube.
- UF Health Pathology Laboratories, Routine Venipuncture Guidelines · A university lab’s CLSI order of draw, the discard-tube note for winged sets, and mixing.
- University of Michigan MLabs, Order of Draw for Multiple Tube Collections · Tube groups, pink EDTA for blood bank, gray tube for lactate.
- UCSF Clinical Laboratories, Specimen Collection · Blood cultures first, citrate fill volume, discard tube with a winged set.
- Labcorp, Blood Specimens: Coagulation · The 9:1 blood-to-anticoagulant ratio, under-filling, and the discard tube with a winged set.
- Labcorp test listings (CBC 005009; also PT 005199, aPTT 005207, hemoglobin A1c 001453, lactic acid 004770) · The tube pairings in the questions: CBC and A1c (EDTA), PT and aPTT (citrate), lactate (gray, on ice).
- ARUP Laboratories, Lactate, Plasma (3019650) · Gray fluoride-oxalate tube in an ice bath, plasma separated within 15 minutes.
- Bazzano et al., The Order of Draw during Blood Collection: A Systematic Literature Review (2021) · What EDTA carryover does to results, and what the studies say about how often it happens.
- DailyMed, Heparin Sodium Injection prescribing information · Section 12.1: how heparin works through antithrombin.
- Alberta Precision Laboratories, Skin Puncture Order of Collection (PA03-010) · The capillary order, citing CLSI GP42.
Questions
Common questions
Yes. The chart, the drill and the ten practice questions are free, and your result needs no sign-up. An email unlocks the bonus: a printable badge card, the skin-puncture order and 20 more questions.
Because the additive in one tube can be carried into the next tube and change its result. The classic example is EDTA: a trace of it in a chemistry sample can read as high potassium and low calcium, and in a citrate tube it can lengthen clotting times. How often that happens with modern closed (vacuum) systems is debated. A 2021 systematic review found the studies disagree: the most recent ones call carryover unlikely in a closed system, some earlier ones found EDTA contamination relatively common, and the review called the evidence too thin for a firm conclusion. The standards and the lab manuals keep the order, and so does this page.
Yes. The colors here are the common conventions, but they can differ by manufacturer and by lab, and so can the exact placement of tubes that are not in the standard six groups. The WHO guideline says to verify its recommendations, the color codes and the additives with the local laboratory, and so do we.
Use it to study. On the bench, your lab’s procedure manual and your trainer come first, and they decide the tubes, the fill volumes, the inversions and any discard tube. This page takes no patient details and is not a collection procedure.
The venipuncture order as CLSI GP41 is commonly summarized: blood culture bottles, sodium citrate, serum tubes (with or without clot activator or gel), heparin tubes, EDTA tubes, then the sodium fluoride tube. The university lab manuals in the sources use these same six groups. The WHO guideline’s table, which is based on the 2003 consensus, runs the same way with one extra step: a plain tube with no additive between the culture bottles and citrate, which CLSI still allows for glass tubes or plastic tubes with no clot activator.
No. For a finger or heel puncture, lab summaries of CLSI GP42 fill the blood gas tube first, then the EDTA tube, then the other additive tubes, then serum. The WHO guideline puts it simply: the hematology specimen first, then chemistry and blood bank, to minimize the effects of platelet clumping, which makes it roughly the reverse of the venipuncture order. The bonus shows the two side by side.