Phlebotomy order of draw

This is the routine venous phlebotomy order of draw, as published by the Clinical and Laboratory Standards Institute (CLSI). Tube colors are examples — always confirm the additive on the label and follow your laboratory's collection instructions.

Sequence: CLSI, Order of Blood Draw Tubes and Additives. Color examples: BD tube guide. Venous collection only: capillary collection has a different order. A first citrate specimen through an unprimed butterfly set needs the discard step.

Last verified: September 14, 2026 — the linked collection guidance, device examples, and standard-edition records. This is a study reference, not a substitute for supervised training, your laboratory's procedure, or the device instructions.

Abbreviations: EDTA = ethylenediaminetetraacetic acid; SST = serum separator tube; PST = plasma separator tube; RST = rapid serum tube.

Draw the tubes you were asked for, not the whole chart

The six positions are a relative order. Sort the tubes you actually have, then collect them in that relative order.

Worked example. The order is a complete blood count (CBC), a comprehensive metabolic panel, and a prothrombin time/international normalized ratio (PT/INR). For this example, the laboratory specifies three tubes: lavender (EDTA), gold SST (serum), and light blue (citrate). Their positions are 5, 3, and 2. So you draw light blue → gold SST → lavender. You do not add a blood culture bottle or a gray tube just because those groups appear on the chart.

The example assumes routine straight-needle collection. With an unprimed butterfly set and citrate first, add the tubing-fill discard step. A test's container requirements come from the laboratory, not from its name alone. CLSI; BD collection instructions.

A question can give you three tubes and ask for their order. The mnemonic gives you six words. You have to sort, not recite.

Each position protects something

If you memorize only the colors, a reworded question ("which tube comes immediately before the lavender?") can knock the whole sequence out of your head. Attach the additive and its purpose to the position, not just a color.

Walk it once:

• Cultures go first as part of minimizing contamination. First position alone does not make a collection sterile: skin and bottle-septum preparation still matter. CLSI; CDC collection guidance.
• Citrate goes second in the routine sequence, ahead of clot activators and the later anticoagulants that could interfere with coagulation testing. CLSI.
• Serum tubes go third. Serum tubes with a clot activator must follow citrate; genuinely nonadditive serum tubes have the specific exception explained below. CLSI.
• Heparin goes fourth. It is an anticoagulant, and carryover into a coagulation specimen can interfere with testing. Collection-interference review.
• EDTA goes fifth. With potassium-EDTA contamination, potassium can read falsely high while calcium reads falsely low. That describes actual contamination, not an automatic consequence of every reversed draw. Experimental evidence.
• Gray goes last among these six routine groups. Fluoride/oxalate contamination can affect hematology measurements. Specialty tubes outside the chart still require their own collection instructions. CLSI; Collection-interference review.

Common tests are examples, not tube-selection instructions

The same test name does not guarantee the same accepted container at every laboratory. Use the additive group to sort the tubes after checking what the ordered tests require.

These are additive/use examples from BD, the EDTA research overview, and the cited laboratory methods, not a complete test directory. The BD instructions also limit the use of separator-gel tubes for certain drug assays. Labcorp's ESR method uses lavender EDTA, and its plasma lactate method specifies gray fluoride-containing tubes. Ammonia is not a universal green-top test: Labcorp's Ammonia, Plasma test 007054 accepts EDTA as its only anticoagulant.

Which mnemonic should you use?

"Studious Boys Rarely Get Low Grades" (Sterile, Blue, Red, Green, Lavender, Gray). Six words, six positions, no overlap.

Our recommendation: pick one six-word version and keep it, because CLSI publishes six groups, and a six-word cue maps onto them one for one. "Red" stands for the serum group, not a requirement to draw a red tube before a gold tube. "Blue" means the light blue citrate group, not every blue-colored closure. CLSI.

One more habit: rehearse it from the middle. Ask yourself "what comes after the green tube?" and then practice sorting only the tubes named in a question. Keep this cue for routine venous collection, not a finger stick or heel stick.

Five cases the mnemonic doesn't cover

A color-only cue cannot settle these cases. The additive, collection method, and test instructions can.

Butterfly set with a citrate tube first? Use a discard tube

The tubing on an unprimed winged ("butterfly") collection set holds air. If the light blue citrate tube is the first specimen on that set, the air can leave the tube short of its intended fill — which throws off the blood-to-anticoagulant ratio and can falsely prolong clot-based results.

The fix is a discard tube drawn first, just to push blood into the tubing's dead space. It does not need to be filled completely. It should be a nonadditive or a coagulation tube, and the amount collected must be enough to fill the tubing. There is no one discard volume for every set. BD collection instructions, Recommended Order of Draw.

Do not use a red top that contains a clot activator for this. BD's instructions identify SST and Plus Serum/CAT clot-activator tubes as additive tubes that must not be used as discards before citrate specimens. A genuinely nonadditive plastic tube is different; read the label rather than rejecting or accepting a tube by color alone. BD instructions, clot-activator discard restriction; CLSI.

Outside that situation, a discard tube is not routinely required before a coagulation sample (Labcorp, Blood Specimens: Coagulation). This is also a different thing from clearing an indwelling line, which has its own procedure.

Rule: unprimed butterfly + citrate first = an appropriate discard first, enough to fill the tubing, not necessarily a full tube.

Does red come before or after light blue?

Both answers are in print, and the difference is the tube, not the teacher.

CLSI's rule is that only a blood culture tube, a glass nonadditive serum tube, or a plastic serum tube without a clot activator may be collected before the coagulation tube. A plain glass red with genuinely no additive qualifies. A plastic red top with a clot activator and a gold SST do not. CLSI.

The material alone does not decide it. In a question that identifies a clot-activator red top, put it after citrate. If it explicitly identifies a genuinely nonadditive serum tube, apply that stated exception instead of assuming that every red top is identical.

Rule: clot-activator serum after citrate; a genuinely nonadditive serum tube is the specified exception.

Yellow is two completely different tubes

A yellow closure tells you almost nothing on its own.

• Yellow with SPS is a blood culture tube. It belongs in the first group.
• Yellow with ACD (acid citrate dextrose) is used for blood bank studies, human leukocyte antigen (HLA) typing, and DNA and paternity testing. It is not a culture tube and it does not automatically go first.

The two additives appear on BD's SPS specification and ACD specification; the test-use examples appear in the BD tube guide.

ACD isn't one of the six listed positions. Place it the way CLSI says to place any unlisted tube — by its additive and by the collection instructions for the test that was ordered. Neither "all yellow first" nor "all yellow last" is a real rule. CLSI.

Royal blue, tan, pink, pearl: go by the additive

Same principle: a closure color is not an additive.

CLSI's guidance for tubes not on the six-position list is to consider what their additive could do to the next tube. So:

• A royal blue with a clot activator is a serum tube → position 3.
• A royal blue with K₂EDTA is an EDTA tube → position 5.
• A tan labeled K₂EDTA joins position 5, with the other EDTA tubes.

BD lists the two royal-blue examples separately: serum clot activator and K₂EDTA. Mayo's trace-metal collection instructions identify a tan K₂EDTA lead tube. Pink and pearl/white examples also use EDTA, but check the actual label and ordered test. BD tube guide.

Mayo Clinic Laboratories instructs that when several specimens are scheduled, the royal blue tube should be drawn first within its additive group. That is a royal-blue instruction in Mayo's trace-metal procedure, not proof that every tan tube must precede every lavender tube. Check the laboratory's instructions for the particular lead or trace-metal test. Mayo, page 1, Order of Draw.

Ignore any chart that gives royal blue one fixed position regardless of what's inside it.

Rule: read the label, find the additive, join that group, then apply the test's special collection instructions.

Capillary collection uses a different order

A finger stick or heel stick is a different method with its own standard, CLSI GP42, Collection of Capillary Blood Specimens, 7th edition (September 2020). Do not apply the venous sequence to it.

For the blood-gas and microcollection specimens below, use this order:

The explanation published by Nancy Glasgow-Roberts, chair of the GP42 seventh-edition committee, puts blood gases ahead of EDTA. Clinical society guidance corroborates the sequence, and the University of Florida's microcollection instructions specifically put serum-separator containers after anticoagulant specimens. Dried-blood-spot and newborn-screening collection has separate instructions and is not part of this four-row chart.

Clotting and platelet clumping can compromise a capillary hematology specimen, so EDTA collection is early. Serum specimens are intended to clot and are collected later. The serum-separator tube's clot activator does not move it into the earlier "other additive" position. Clinical society guidance; UF microcollection order.

Capillary blood should go into capillary collection devices, not be transferred into venipuncture tubes. Capillary-device guidance.

This distinction also appears in official exam materials: the ASCP Board of Certification's PBT content guideline lists venous and capillary order separately, and NHA's CPT test plan includes separate venipuncture and capillary collection tasks. These establish topic coverage, not a claim that this page covers either entire exam.

Rule: if a question says heel stick, finger stick, or capillary microcollection, use the capillary sequence, not the venous mnemonic.

Correct order isn't the same as correct fill and mixing

These are separate checks. Getting the sequence right does not fix the other two.

Fill. A routine citrate coagulation tube needs 9 parts blood to 1 part anticoagulant. Fill it to the indicated volume. Underfilling raises the anticoagulant-to-blood ratio and can extend clot-based assays. Never combine two underfilled tubes to make one full one — each tube carries its own anticoagulant, so combining them doesn't fix the ratio. If a tube is short, follow your lab's acceptance and recollection procedure. A hematocrit above 55% requires the laboratory's citrate-adjustment procedure rather than applying the routine ratio without review. Labcorp coagulation instructions.

Mixing. Invert gently, immediately, the number of times the tube's manufacturer specifies — and those counts differ by tube type and by manufacturer. Don't shake; vigorous mixing can cause foaming or hemolysis. Inadequate mixing can cause clots in anticoagulant tubes and delayed clotting in serum tubes. BD collection instructions, step 13.

Device-specific inversion counts

These are the counts for the products listed on BD's June 2023 order-of-draw chart, not a universal table for every tube with the same color.

Source: BD chart, mixing column and footnotes. PPT means plasma preparation tube. Specialty tubes and culture bottles require their own device instructions; do not extend these figures to every royal-blue, tan, or blood-culture container. Labcorp specifies 3–6 inversions for its citrate collection procedure, illustrating why the named device and laboratory instructions matter. Resolve a discrepancy with your supervisor rather than averaging two instructions. Labcorp.

Backflow. Preventing additive-containing blood from flowing back toward the patient is a separate safety requirement. BD's instructions: keep the patient's arm downward, hold the tube with the stopper uppermost during collection, release the tourniquet as soon as blood starts flowing, and prevent the additive from contacting the stopper or end of the needle. These precautions do not replace the recommended order. BD, Prevention of Backflow.

What an out-of-order draw does — and what it doesn't prove

A reversed sequence is a collection deviation; it is not proof that contamination occurred or that every affected result changed.

The clearest distinction is between confirmed potassium-EDTA contamination and a tube drawn after EDTA. With sufficient contamination, potassium can read high and calcium low because potassium-EDTA adds potassium and EDTA binds calcium. That pattern can raise suspicion; it cannot, by itself, establish contamination or justify dismissing an abnormal patient result. Experimental evidence; Closed-system observational study.

A 2021 systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework and included 11 studies. Its authors classified seven as finding negligible importance for order in preventing cross-contamination and four as supporting its necessity. They emphasized differences between open and closed collection systems and said the limited, heterogeneous evidence did not support strong conclusions. Those are study classifications, not a patient-level contamination rate.

The review describes possible carryover through direct tube-to-tube transfer, reflux through collection equipment, or a syringe needle contaminated while filling tubes. Do not pour whole blood between additive collection tubes to "fix" a draw or a fill problem. That is different from the laboratory's specified processing of a properly collected specimen into an appropriate transport container. Review, Introduction; Labcorp.

None of that makes the sequence optional. Follow the applicable laboratory procedure and device instructions. Correct order also does not prevent every other collection error: adequate citrate fill, a required winged-set discard, gentle mixing, and aseptic culture technique are separate requirements. CLSI; BD; CDC.

If you realize you drew out of order: don't decide on your own whether the specimen is usable, and don't try to rescue it by transferring whole blood into another additive tube. Tell the laboratory what happened and follow its specimen-assessment and recollection procedure. The actual tubes, tests, and collection conditions determine the response.

Practice questions

Twenty-five original, unofficial questions — not questions from any certification exam. The scenarios are hypothetical. This is a topical self-check, not a full-length exam; any percentage you calculate is feedback on these 25 items, not an official exam score or a prediction of passing.

Answers and explanations are on this page. Nothing to unlock, nothing to sign up for.

For anything you missed, go back to the section linked in the explanation and try that question again before moving on.

Is your handout out of date?

PRE02, eighth edition, is the current CLSI venous collection standard listed in its catalog. It replaces GP41, seventh edition. Capillary collection remains a separate standard, GP42. CLSI PRE02; CLSI GP42.

A GP41 citation signals an older reference; it does not, by itself, tell you whether the handout's actual sequence is wrong. Compare the additive groups and exceptions, and ask your instructor or laboratory about any discrepancy. The brief list of changes on a catalog page is not proof that every detailed requirement stayed the same.

Sources

The linked passages and device examples were checked on September 14, 2026. Source dates are not replaced by the date of this check.

• Collection standards and sequence: CLSI's public six-group venous explanation; PRE02 eighth-edition catalog and public sample; GP42 seventh-edition catalog and public sample. The full paid standards were not accessed.
• Device and laboratory instructions: BD archived 2021 collection-system instructions; BD June 2023 order/mixing chart; Labcorp coagulation instructions. Figures are tied to the named source and device, not presented as universal mixing rules.
• Additive and specialty-tube examples: BD's dated tube guide; current yellow SPS and yellow ACD specifications; current royal-blue clot-activator and royal-blue K₂EDTA specifications; Mayo trace-metal instructions, page 1. Mayo's cited passage concerns additive grouping and royal-blue priority, not a universal tan-tube rule.
• Capillary collection: Glasgow-Roberts, Best practices in capillary blood collection, January 2021; clinical society recommendations, Recommendation 16.1, 2015; University of Florida microcollection order.
• Contamination and evidence: CDC culture-contamination guidance and culture-collection procedure; Lima-Oliveira et al., experimental K₂EDTA contamination, 2014; Ercan et al., closed-system observational study, 2021; Bazzano et al., systematic review, 2021.
• Exam-topic and test-directory checks: ASCP PBT content guideline, revised September 25, 2025; NHA CPT test plan, based on the 2024 job analysis; Labcorp's ESR, lactate, and ammonia specimen requirements. Exam plans establish subject coverage; clinical and laboratory sources support the explanations.

Written by the Castleport Test Prep Editorial Team. AI tools assisted with drafting and source-based editorial checking. We checked the linked public sources within the scope described above; we did not observe a laboratory workflow or conduct a clinical or professional review of this page. Our editorial standards distinguish source verification from qualified subject-matter review.

Castleport Test Prep is an independent exam prep publisher. We are not affiliated with, endorsed by, or approved by the Clinical and Laboratory Standards Institute, the National Healthcareer Association, the ASCP Board of Certification, or Becton, Dickinson and Company. Exam, credential, and product names are used to identify their subjects; trademarks belong to their respective owners. The practice questions here are original and unofficial. This page does not certify clinical competence and does not guarantee any exam result.