Order of Draw Quiz: 12 Free Phlebotomy Questions
Twelve questions on the order of draw: which tube comes first and last, where the pink, green and gray tops go, when a butterfly needs a discard tube, how many times to invert each tube, and the different order for capillary collection. Every answer follows the order of draw guide (CLSI PRE02-Ed8) and is explained, wrong options included. No account needed.
Written by Benjamin Tibbs, a phlebotomy studentChecked against CLSI, OSHA, CDC and The Joint CommissionUpdated October 2026
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Answer: C. Light blue (sodium citrate)
With no blood cultures, the light blue citrate tube is first, then the gold serum tube, then the lavender EDTA tube (CLSI PRE02-Ed8; BD). Citrate goes ahead of clot-activator and EDTA tubes so neither additive can be carried into the coagulation tube and change its results.
Why the other choices are wrong
- A. EDTA binds calcium and would be carried into later tubes, so lavender comes near the end of the order.
- B. Clot activator carried into the citrate tube can shorten clotting times, so the serum tube follows the light blue.
- D. The order of draw applies to every multi-tube draw, not only when cultures are ordered.
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Answer: A. Gray
The order is green (heparin), then lavender (EDTA), then gray (fluoride/oxalate) last. Oxalate binds calcium and fluoride affects cells and some enzymes, so gray-top additives must not be carried into any other tube.
Why the other choices are wrong
- B. Green (heparin) comes before both lavender and gray.
- C. Lavender comes after green but before gray.
- D. Additive carryover makes the order matter for these three as for any others.
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Answer: D. After the gold, before the lavender
The sequence is blood cultures, citrate (light blue), serum (red, gold or SST), heparin (green or light green PST), EDTA (lavender or pink), then fluoride/oxalate (gray). Heparin tubes come after serum tubes and before EDTA tubes.
Why the other choices are wrong
- A. Blood cultures and the citrate tube come before any heparin tube.
- B. Serum tubes come between the citrate and heparin tubes.
- C. Heparin comes before EDTA. EDTA carried into a heparin tube falsely raises potassium and lowers calcium.
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Answer: B. With the lavender, since both contain EDTA
Pink-top tubes contain K2EDTA, like lavender tops, so they take the EDTA position in the order of draw, after citrate, serum and heparin tubes. Here that means the light blue first, then the pink and lavender tubes.
Why the other choices are wrong
- A. A test's importance does not change additive carryover. Pink tubes contain EDTA and are drawn in the EDTA position.
- C. Gray is last. Pink belongs with the other EDTA tubes.
- D. Drawing an EDTA tube before the citrate tube risks EDTA carryover into the coagulation specimen.
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Answer: C. No, not for a routine PT with a straight needle
A discard tube is needed when a butterfly is used and a citrate tube is the first tube, to clear the air from the tubing so the tube fills to its line. With a straight needle, a discard tube is not needed for routine PT or aPTT testing. The tube must still be filled to its line to keep the 9:1 blood-to-citrate ratio.
Why the other choices are wrong
- A. The discard tube exists to clear air from butterfly tubing. A straight needle has no tubing.
- B. A clot-activator tube before citrate is exactly what the order of draw avoids. When a discard is needed, it is a non-additive or another citrate tube.
- D. A half-filled citrate tube has too much anticoagulant and falsely prolongs clotting times.
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Answer: A. Blood cultures, to protect their sterility
Blood culture bottles come first in the order of draw so they are collected before the needle has passed through any other tube's stopper, protecting their sterility. The light blue follows, then the lavender.
Why the other choices are wrong
- B. Citrate is first only when no blood cultures are ordered.
- C. Lavender (EDTA) comes late in the order, because carried-over EDTA alters other tests.
- D. Cultures do come first, but for sterility, not because of their volume.
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Answer: D. Plastic red tubes contain a clot activator
Plastic serum tubes contain a clot activator (silica particles), because blood clots poorly against plain plastic. Carried into a citrate tube, clot activator can falsely shorten clotting times, so serum tubes, plastic red tops included, follow the light blue tube.
Why the other choices are wrong
- A. EDTA is in lavender and pink tubes.
- B. Heparin is in green tubes.
- C. Plastic red tubes do contain an additive, a clot activator, which is why they follow the citrate tube.
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Answer: B. Blood gas, lavender, serum
CLSI GP42-Ed7 gives the capillary order as blood gases first, then EDTA, then other additive tubes, then serum last. Blood starts clotting at the puncture site, so the gas and anticoagulated specimens are collected first; a serum tube is meant to clot, so it goes last.
Why the other choices are wrong
- A. Serum goes last in capillary collection, and the blood gas comes first.
- C. The blood gas is collected first, not last.
- D. The blood gas comes before EDTA in the capillary order.
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Answer: C. 5 times
BD directs 5 gentle inversions for serum tubes (plastic red and SST) to mix the clot activator with the blood. Citrate tubes get 3 to 4, and heparin, EDTA and fluoride tubes get 8 to 10.
Why the other choices are wrong
- A. The clot activator has to be mixed with the blood for the tube to clot completely.
- B. 3 to 4 inversions is the figure for citrate tubes.
- D. 8 to 10 inversions is for heparin, EDTA and fluoride tubes.
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Answer: A. Light blue, gold, lavender, as in the order of draw
Tubes filled from a syringe follow the same order of draw as a direct draw (CLSI PRE02-Ed8), because additive can be carried from tube to tube on the transfer device's needle just as it can on a collection needle. Fill them promptly, before the blood starts to clot in the syringe.
Why the other choices are wrong
- B. EDTA tubes are anticoagulated and do not clot. Lavender goes late to avoid EDTA carryover.
- C. Clot activator carried into the citrate tube can affect coagulation results.
- D. Additive carryover through the transfer device happens just as in a direct draw.
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Answer: D. Light blue, gold, green, lavender, gray
The order is citrate (light blue), serum (gold), heparin (green), EDTA (lavender), then fluoride/oxalate (gray), with blood cultures ahead of all of them when ordered (CLSI PRE02-Ed8; BD).
Why the other choices are wrong
- A. Gold before light blue risks clot activator getting into the coagulation tube.
- B. Serum (gold) comes before heparin (green), and EDTA (lavender) comes before gray.
- C. Lavender first would carry EDTA into every tube that follows.
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Answer: B. To prevent additive carryover from one tube into the next
Additive can cling to the needle and be carried into the next tube. The order of draw sequences tubes so a carried-over additive cannot change the next tube's results; for example, EDTA (which binds calcium and contains potassium) never comes before a chemistry or coagulation tube. Blood cultures go first for sterility.
Why the other choices are wrong
- A. The order does not change the speed of the draw. It exists to prevent carryover.
- C. The sequence is set by the additives, not by which test seems most important.
- D. Laboratory workflow does not set the order of draw; additive carryover does.
Where these answers come from
Each question was checked against the standard named in its explanation. The sources used in this set:
- BD Vacutainer order of draw and mixing guide
- BD Vacutainer order of draw guide (EDTA tubes: lavender, pink, PPT); CLSI PRE02-Ed8
- BD Vacutainer order of draw guide (discard tube note); CLSI PRE02-Ed8
- BD Vacutainer serum tube product information; CLSI PRE02-Ed8
- CLSI GP42-Ed7 (capillary order of draw)
- CLSI PRE02-Ed8 (purpose of the order of draw)
- CLSI PRE02-Ed8 (syringe transfer follows the order of draw)
- CLSI PRE02-Ed8 order of draw; BD Vacutainer order of draw guide
More free practice tests
Every set has different questions, each with an explanation and your score by domain. No account needed.
By certification exam
General phlebotomy practice tests
The three phlebotomy certification exams
Question counts, time limits and passing scores from each certifying body's own documents, checked October 6, 2026.
| Exam | Questions | Time | Passing score | Practice |
|---|---|---|---|---|
| NHA CPTNational Healthcareer Association | 120 questions: 100 scored and 20 unscored pretest items | 2 hours | 390 (scaled score from 200 to 500) | NHA CPT practice exam |
| ASCP PBTAmerican Society for Clinical Pathology Board of Certification | 80 multiple-choice questions | 2 hours | 400 (scaled score) | ASCP PBT practice exam |
| AMT RPTAmerican Medical Technologists | 200 scored questions (AMT exams may also include unscored pretest items) | 2.5 hours | 70 (scaled score from 0 to 100) | AMT RPT practice exam |
More detail: how each exam is scored · retake rules · NHA vs ASCP vs AMT · all exam facts with sources
Clinical References
- CLSI PRE02-Ed8 — Collection of Diagnostic Venous Blood Specimens (8th ed., 2025)
- NHA CPT Exam Content Outline (2024)
- ASCP Board of Certification Content Guidelines
- OSHA Bloodborne Pathogens Standard (29 CFR 1910.1030)
- CDC Guidelines for Infection Control in Healthcare Settings