Phlebotomy needle gauge chart
This phlebotomy needle gauge chart groups selected blood-collection sizes by device for US-oriented study, not patient-specific selection. A higher gauge number means a thinner needle, and the colour on the hub is a manufacturer's shortcut — the gauge printed on the packaging is what counts.
The chart
| Device | Gauge (nominal outer diameter) | Needle / tubing length | Colour on identified examples | Source-defined context—not a patient-specific prescription |
|---|---|---|---|---|
| Straight multisample needle (evacuated tube system) | 20 G (0.9 mm) | 1 in, 1¼ in or 1½ in | Yellow — Greiner VACUETTE | Selected high-volume or rapid collections in stable adults with strong, healthy veins in Greiner’s instructions. |
| Straight multisample needle | 21 G (0.8 mm) | 1 in, 1¼ in or 1½ in | Green — Greiner VACUETTE | Routine adult option; preferred for healthy adult veins in Greiner’s instructions. |
| Straight multisample needle | 22 G (0.7 mm) | 1 in, 1¼ in or 1½ in | Black — Greiner VACUETTE | Adults, and smaller or more fragile veins, in Greiner’s instructions. |
| Winged ("butterfly") blood collection set | 21 G (0.8 mm) | ¾ in needle; 7 in or 12 in tubing in the listed BD range | Green — BD UltraTouch 368689 | Adult option in the standard BD Push Button Instructions for Use (IFU); not inherently thinner than a straight needle. |
| Winged set | 23 G (0.6 mm) | ¾ in needle; 7 in or 12 in tubing in the listed BD range | Light blue — BD UltraTouch 368688 | Small or difficult-vein contexts; the standard BD IFU includes adult, pediatric and neonatal groups. This is not an age-only selection rule. |
| Winged set | 25 G (0.5 mm) | ¾ in needle; 7 in or 12 in tubing in the listed BD range | Dark blue — BD UltraTouch 368687; orange — Greiner EVOPROTECT 450132 | Device-specific use. The standard BD IFU cautions that 25 G may increase hemolysis. Different 25 G devices do not share one wall design. |
| Syringe with a hypodermic needle | 21–23 G examples in WHO’s 2010 table | Read the needle’s own length label | Read the marked size, not a tube-cap colour | A different collection/transfer system, not a separate gauge scale. WHO table; BD syringe precautions. |
| Whole-blood donation (different collection purpose) | 16 G in WHO’s donation guidance; 16–18 G in its table | Needle usually supplied with the collection bag | Not a diagnostic-draw colour key | Donation context, not a routine diagnostic-draw recommendation. WHO, 2010. |
| Capillary / dermal puncture | Some lancets also carry a gauge | Puncture depth is a separate specification | Device-specific | BD’s 21 G × 1.8 mm fingerstick lancet disproves “lancets have no gauge.” A venous needle chart does not select a heel lancet. |
Where each row comes from. Straight-needle dimensions and colours are from the Greiner catalogue; winged-set dimensions are from BD’s reference table and the linked specifications. The millimetre figures are the labels manufacturers print, not measurements with tolerances. The Greiner examples include international catalogue entries; they do not establish US stock. Manufacturer names identify the specification being cited.
The selection principle: the assessed vein, required collection and applicable device instructions matter. Not the thinnest you own, and not the one you always reach for. Greiner’s June 2025 IFU includes 20 G use that the older WHO table does not; the historical table is not a complete list of current devices.
Why the same number means different devices
Gauge describes the outside diameter of the steel. It does not describe the device. A 23 G exists as a winged set; it is not sold as a straight multisample needle in the catalogues above. That is a statement about those catalogues, not proof that a 23 G or 25 G needle can exist only as a butterfly. A broad gauge range is not useful until you know whether a chart means diagnostic collection, donation, injection or another task. Straight-needle examples; winged-set examples.
The numbering also runs backwards, and the steps are not even. Greiner Bio-One's technical note puts the range plainly: a 10 G needle is 3.4 mm across and a 20 G needle is 0.9 mm.
So when you compare two needles, compare the millimetres in your head, not the gauge numbers. 21 G (0.8 mm) is wider than 22 G (0.7 mm), which is wider than 23 G (0.6 mm). Say "higher gauge number" or "thinner needle." "Bigger needle" gets people into trouble on exams and at the bench. Greiner nominal sizes; BD nominal sizes.
How to read a needle label
Three numbers can appear on one package, and they measure three different things.
Example 1 — a straight needle: 21 G × 1 in
Greiner's item 450072 is a VACUETTE Multiple Use Drawing Needle 21G × 1", green, also printed as 0.8 × 25 mm.
- 21 G is the gauge — the outside diameter class.
- 1 in is the length of the needle itself.
- 0.8 × 25 mm is the manufacturer's nominal metric label: diameter first, length second. It is not an exact inch-to-millimetre conversion.
- Green is that catalogue's colour for 21 G. It tells you nothing about the length.
Example 2 — a winged set: 23 G × ¾ in with 12 in tubing
BD's item 368688 is a Vacutainer UltraTouch Push Button Blood Collection Set, and its specification page lists Needle Gauge 23 G, Needle Length 3/4 in., Wing Color Light Blue, with 12 in. of tubing.
- 23 G is the gauge.
- ¾ in is the needle — the part that enters the vein.
- 12 in is the tubing between the needle and the tube holder. It is not needle length.
One caution on units: WHO's 2010 table pairs inches with centimetre figures that don't convert correctly — it prints 0.5 inch as "0.75 cm" when half an inch is 1.27 cm. Use the manufacturer's own dimensions rather than copying those conversions. The calculation is 0.5 × 2.54, using NIST's inch-to-centimetre factor.
Gauge does not tell you wall thickness
Wall thickness. Greiner's technical note explains it in one line: although the gauge stays the same, a thinner wall gives a larger inner diameter. The inner opening is also called the lumen. Steel tubing comes in regular, thin, extra-thin and ultra-thin wall versions; Greiner discusses those classes with reference to ISO 9626.
That distinction matters when you compare devices. It does not mean every device with the same gauge or a similar wall description performs identically.
Is a butterfly always smaller?
No. "Butterfly" names a design — a winged needle on flexible tubing — not a gauge. The winged sets in the catalogues above come in 21 G, 23 G and 25 G. BD reference table; Greiner device overview.
Put two real products side by side and the assumption falls apart: a 21 G winged set is 0.8 mm, and a 22 G straight needle is 0.7 mm. The winged one is the wider needle. Wings don't reverse the scale. Winged-set dimensions; straight-needle dimensions.
The tubing also adds a specification that a straight needle does not have. Its length and priming volume belong to the whole set, as the dead-space example below shows.
What the colours really tell you
Enough to be useful inside one product line. Not enough to identify an unfamiliar needle.
| What you might assume | What the sources actually show |
|---|---|
| There's one universal colour key for every blood-collection device | ISO 6009:2016 concerns colour identification of single-use hypodermic needles. Its scope alone does not establish a universal colour key for every component of a winged collection set. |
| Straight-needle colours always differ by brand | Here they agree: Greiner lists 20 G yellow, 21 G green, 22 G black, and BD names its two Eclipse safety needles “21 G green shield” and “22 G black shield.” Greiner; BD. |
| 25 G butterflies are always orange | BD’s 25 G UltraTouch has dark-blue wings; the identified 25 G Greiner EVOPROTECT is orange. These are different devices, not conflicting measurements of one product. |
| A needle's colour tells you which tube to use | Needle-size identification and tube-additive identification are different tasks. Read the tube label and applicable tube instructions; do not match a needle’s colour to a stopper. Greiner tube identification. |
On an unfamiliar pack, read the printed gauge. Every time.
Does a thinner needle mean a hemolysed sample?
Not by itself. Hemolysis is the breakdown of red blood cells, which can affect laboratory results; gauge alone does not describe every cause. WHO’s specimen-quality discussion includes both a needle that is too small and a needle too large for the vessel. Both directions matter.
The device matters, not just the number. Thin-wall construction can provide a wider inner channel at a given outside gauge. The 2023 study describes its tested 25 G design as maintaining an inner bore similar to a standard 23 G needle. BD’s current UltraTouch specification field says extra-thin wall, while the published studies describe the tested design as ultra-thin-wall. Those descriptions are not a reason to treat all 25 G devices as interchangeable. The Greiner brochure identifies its orange 25 G example as thin wall. BD specification; 2017 study.
What the research found. A 2023 comparison in cancer patients did not detect increased hemolysis with a specific 25 G UltraTouch set versus a standard 23 G set (P = 0.5). That is not proof that every 25 G device preserves every specimen, or that the devices are identical. The 2023 record lists academic affiliations and National Institutes of Health (NIH) grant support. An earlier device-specific study also reported no increase in measured hemolysis indicators; its author list includes five BD-affiliated researchers and one hospital-affiliated researcher.
So what do you do with that?
- "25 G always ruins the sample" is no longer supportable as a blanket rule.
- "Any 25 G is fine now" was never supportable either. The evidence attaches to specific devices, not to the number 25.
- Check the exact device instructions and follow your facility's written procedure; a similar gauge or wall label is not enough.
The standard BD Push Button IFU itself cautions that 25 G use may increase hemolysis. It also warns that drawing into a syringe may increase hemolysis, and specifies a blood transfer device for filling tubes from a syringe. Those instructions are not erased by a study of another device.
The butterfly's hidden cost: dead space
Tubing holds air before blood reaches the first tube. BD publishes the volume needed to prime its standard Push Button Blood Collection Set in Table 1 of the IFU:
| Tubing length | 21 G | 23 G | 25 G | 21 G-to-25 G difference |
|---|---|---|---|---|
| 7 in | 0.228 mL | 0.225 mL | 0.224 mL | 0.004 mL |
| 12 in | 0.353 mL | 0.350 mL | 0.349 mL | 0.004 mL |
| Difference across lengths | 0.125 mL | 0.125 mL | 0.125 mL | — |
Do the division and the lesson is clear. In this table, changing 21 G to 25 G moves the listed priming volume by 0.004 mL. Changing from 7-inch to 12-inch tubing moves it by 0.125 mL — 31.25 times as much. Dead space is a property of the whole set, not the gauge alone. This is a comparison of published specifications, not a universal butterfly-volume formula.
That is why the first citrate tube needs special attention with an unprimed winged set. BD’s instruction calls for a discard tube first to fill the tubing’s dead space; it does not have to fill completely. That instruction and the Greiner US tube IFU allow a nonadditive or coagulation discard tube. The Greiner international IFU specifies a No Additive tube instead, so use the instruction applicable to the actual system and region. The purpose is to protect the citrate specimen’s intended blood-to-additive ratio, not to add an arbitrary discard volume to every draw.
One more device distinction: the 12-inch UltraTouch sets list higher priming volumes than the standard sets at the same gauge and tubing length — 0.354 mL rather than 0.350 mL at 23 G, and 0.351 mL rather than 0.349 mL at 25 G. A wider inner channel can hold more, but those catalogue values alone do not isolate the cause of the difference. Use the specification for the exact set, not a value borrowed from another model.
How to check a conflicting chart
Look for a named device, a collection purpose and a source date before memorising a size rule.
| The claim | What to check |
|---|---|
| “Phlebotomy needles run 14 G to 30 G” | Ask which devices and procedures the range covers. A mixed range does not tell you which size belongs to diagnostic collection, donation or another task. WHO’s context table; identified drawing needles. |
| “19–20 G is not applicable, so 20 G can never be used” | That N/A entry comes from WHO’s 2010 table. The June 2025 Greiner IFU expressly describes selected 20 G adult use. The old table is not a current prohibition. |
| “18 G is the routine diagnostic entry in WHO’s table” | The 16–18 G entry is in the blood-donation context. The inspected Greiner 18 G catalogue entries are labelled veterinary use only. Neither fact establishes a universal rule about every 18 G device. |
| “Yellow means 21 G” | Not in the straight-needle examples here: Greiner lists yellow as 20 G and green as 21 G; BD names its 21 G Eclipse the green shield. Greiner; BD. |
We're describing claims, not ranking websites. If you find one of these on a page you were about to study from, check the rest of it too.
Which CLSI standard replaced GP41?
CLSI PRE02, eighth edition, published February 13, 2025, replaced CLSI GP41-Ed7 from 2017 — and the code itself changed from GP41 to PRE02. CLSI's own record identifies the current edition; its free sample title page explicitly identifies the replacement.
If your textbook, your lab's standard operating procedure (SOP) or a study guide cites "CLSI GP41," that's the superseded code. So does BD's own 2023 winged-set IFU, which was written before the change. It doesn't make either document useless — it tells you how old the reference is.
Mayo Clinic Laboratories’ 2020 discussion reported a historical wording change from any to some 25 G needles in GP41-era guidance. That is not a quotation from current PRE02. The CLSI sources linked here establish the edition change, not the wording of PRE02’s needle-selection requirements.
Where this shows up on your exam
For the National Healthcareer Association (NHA) Certified Phlebotomy Technician (CPT) exam, the test plan explicitly lists needle gauge sizes and lengths under Routine Blood Collections, knowledge statement k56. Equipment-selection considerations appear immediately before it at k55. This plan is based on the 2024 job analysis and applies to the exam launched January 7, 2026.
The plan does not publish a separate allocation of questions just for needle gauge. Use this chart as a focused equipment reference, not as a complete review of that domain or an official exam answer key.
Ten questions on needle selection
Original Castleport practice items, written to the sources on this page. They are not actual exam questions, not recalled items, and not a readiness score. Ten questions can't tell you whether you'll pass anything.
Question 1
A 34-year-old with a prominent median cubital vein needs four tubes. Which straight multisample option matches the preferred healthy-adult gauge in Greiner’s June 2025 instructions?
A. A 25 G winged set with 12 in tubing
B. A 21 G straight multisample needle
C. A 16 G needle attached to a collection bag
D. A 23 G winged set drawn into a syringe
Reveal answer
B — a 21 G straight multisample needle.
Greiner’s IFU identifies 21 G as its preferred option for healthy adult veins. A and D are winged systems, not the straight multisample option asked for; C is a donation setup. This tests the stated manufacturer guidance, not a rule that a prominent vein can never benefit from a winged set. Actual selection still depends on the assessed vein and the applicable procedure.
Question 2
In WHO’s 2010 needle-selection table, which of these options appears in the neonatal venipuncture column—not the heelstick procedure?
A. 21 G straight needle
B. 22 G straight needle
C. 23 G winged set
D. 18 G straight needle
Reveal answer
C — a 23 G winged set.
The 23 G winged-set entry is the only one WHO ticks in the neonatal column. 22 G is ticked for adults and for paediatric, elderly and small veins — but not neonates. 21 G is adult-only in that table. 16–18 G sits in the blood-donation row. This is a question about the dated table, not proof that it lists every currently available neonatal collection device.
Question 3
Which statement best matches the evidence about 25 G winged sets?
A. Every 25 G set raises hemolysis risk
B. 25 G is never acceptable for adults
C. Device design and collection conditions matter; the gauge number alone does not establish hemolysis risk
D. A 25 G set eliminates hemolysis
Reveal answer
C — it depends on more than the gauge number.
A 2023 comparison did not detect increased hemolysis with one specific 25 G design versus a standard 23 G device. That does not validate every 25 G set or collection condition. A overgeneralizes risk; B invents a blanket adult prohibition; D turns a limited finding into a guarantee. The standard BD Push Button IFU still carries a 25 G hemolysis caution. Wall thickness is one design feature, not the only variable.
Question 4
An unused winged set has not been primed, and the first specimen tube ordered is a citrate coagulation tube. What do the cited manufacturer instructions require before filling that specimen tube?
A. Nothing extra — draw the citrate specimen immediately
B. Draw a discard tube first to fill the tubing’s dead space
C. Always switch to a straight needle
D. Overfill the citrate specimen tube to compensate
Reveal answer
B — draw a discard tube first.
The tubing holds air. Filling its dead space first protects the citrate specimen’s intended blood-to-additive ratio. The BD instruction says the discard tube need not fill completely; it and the Greiner US IFU allow a nonadditive or coagulation discard. Other regional IFUs can be narrower, so the applicable device instructions govern the choice. A ignores the air space; C invents a mandatory device switch; D is not an acceptable correction. Overfilling is possible with incorrect transfer and is not a solution to underfilling.
Question 5
On one manufacturer’s sets, priming volume at 23 G is 0.225 mL with 7-inch tubing and 0.350 mL with 12-inch tubing. At 7-inch tubing it is 0.225 mL at 23 G and 0.224 mL at 25 G. Which change has the bigger effect on dead space?
A. Changing the gauge
B. Changing the tubing length
C. They’re about equal
D. Neither changes dead space
Reveal answer
B — tubing length.
Length change: 0.350 − 0.225 = 0.125 mL. Gauge change in this question: 0.225 − 0.224 = 0.001 mL. The length difference is 125 times the gauge difference. A is the smaller change, while C and D contradict the supplied numbers. These are calculations from the standard BD set’s listed volumes, not a formula for every butterfly. The 0.004 mL difference in the main table compares 21 G with 25 G, not the 23 G-to-25 G comparison used here.
Question 6
Someone hands you a needle whose hub colour you don’t recognise. What identifies the gauge you are about to use?
A. The hub colour alone
B. The tube stopper colour
C. The marked gauge on the labelled packaging
D. The tubing length
Reveal answer
C — the printed gauge.
The identified 25 G examples already show why A is insufficient: BD UltraTouch has dark-blue wings, while Greiner EVOPROTECT is orange. B concerns a different piece of equipment and its additive identification; D is a length, not a diameter class. Read the printed size and the correct device documentation rather than transferring a colour rule from an unfamiliar product.
Question 7
A study chart copies “16–18 G — routine diagnostic venipuncture” from WHO’s 2010 table. What has it misread?
A. Nothing
B. The range is too narrow
C. 16–18 G appears in the blood-donation context, not the routine diagnostic entries in that table
D. It leaves out 19 G
Reveal answer
C — that’s the donation row.
WHO’s table associates 16–18 G with blood donation, and its donation guidance describes a needle supplied with the collection bag. A accepts the wrong context; B and D change the range without fixing that error. The point is to keep collection purposes separate, not to infer that a particular gauge can never appear in any other device or specialized procedure.
Question 8
BD’s identified fingerstick lancet is labelled 21 G × 1.8 mm. What does 1.8 mm describe?
A. Needle gauge
B. Lancet puncture depth
C. Tubing length
D. A universal safe depth for an infant heelstick
Reveal answer
B — puncture depth.
BD identifies this device’s penetration depth as 1.8 mm. A is the separate 21 G designation; C introduces tubing the label does not describe. D wrongly transfers a fingerstick specification to a different site and patient group. Some lancets do carry a gauge, so “lancets have no gauge” is not a reliable rule. This label-reading example is not a recommendation for heel puncture.
Question 9
Which precaution appears in BD’s standard Push Button Blood Collection Set Instructions for Use about drawing into a syringe?
A. Syringe draws are prohibited
B. Syringe draws require a 25 G needle
C. Using a syringe to draw blood may result in increased hemolysis
D. Syringe draws remove the need for a transfer device
Reveal answer
C — it may increase hemolysis.
The same IFU also specifies a blood transfer device for moving blood from a syringe into collection tubes, so D contradicts its transfer instruction. A is too strong — BD describes the syringe procedure rather than forbidding it. B invents a rule that isn’t there. The warning concerns this collection method; it does not turn one gauge into a universal answer.
Question 10
A study guide cites “CLSI GP41, 7th edition (2017)” as the current CLSI venous blood collection standard. What is its status?
A. Still the current edition
B. Withdrawn with no replacement
C. Replaced by CLSI PRE02, eighth edition, February 2025 — the code changed from GP41 to PRE02
D. Folded into ISO 6009
Reveal answer
C — replaced by PRE02-Ed8.
CLSI’s catalogue identifies PRE02-Ed8, and the sample title page expressly says it replaces GP41-Ed7. A misses the new edition; B misses the replacement. D confuses two different documents: ISO 6009 concerns hypodermic-needle colour identification. This edition check does not establish the wording of any unread clause in the full PRE02 standard.
Common questions
What gauge is used for a normal blood draw?
A 21 G straight multisample needle is a routine adult option for a suitable vein, not a requirement for every adult. Greiner’s instructions identify 21 G as the preferred gauge for healthy adult veins and also describe contexts for 20 G and 22 G.
21 G or 22 G — how do I choose?
By the vein, not by habit. The manufacturer guidance identifies 22 G for smaller or more fragile veins. It does not turn a person’s age into a complete equipment-selection rule; the required collection and applicable procedure still matter.
What gauge is a butterfly needle?
There isn't one. The identified BD families include 21 G, 23 G and 25 G options, with ¾-inch needles and 7-inch or 12-inch tubing. Those lengths describe these examples, not every winged set on the market. BD reference table.
What about children and newborns?
For venipuncture, the 23 G winged set is the only option ticked for neonates in WHO’s 2010 table; the standard BD IFU lists both 23 G and 25 G for pediatric and neonatal groups, with a 25 G hemolysis caution. Those are source-specific descriptions, not instructions to choose by age alone. A heelstick uses a different device, and a lancet may have both a gauge and a depth specification.
Does a thinner needle hurt less?
Not reliably from the number alone. The 2023 cancer-patient study found no significant difference in median pain between its 25 G and 23 G groups. Reports of 3 or higher out of 10 were less frequent with 25 G: 5 of 190 versus 14 of 190. But zero-pain reports were more frequent with 23 G, and scores of 1 or 2 were more frequent with 25 G. That mixed pattern is not a promise of a painless draw, and “3 or higher” should not be relabelled “severe pain.”
What gauge do they use for blood donation?
WHO's 2010 donation guidance describes a 16 G needle, usually attached to the collection bag; its table groups donation under 16–18 G. Donation is a different collection task. Those figures are not a universal current donor-centre policy or a routine diagnostic-draw recommendation.
Next step
Match this chart against the boxes in your own tray. The printed gauge on the packaging is the one that counts, and your facility's written procedure is what governs the choice.
For a label you do not recognise, make three checks: read the gauge, separate needle length from tubing length, and check the exact device instructions. Use the explanations beside any question you missed; there is no score to chase.
Sources
Manufacturer examples identify particular devices and specifications, not a universal equipment list. WHO sources are dated 2010. Research links below lead to the published abstracts and bibliographic records used here.
Device specifications and manufacturer instructions
- Greiner VACUETTE Multiple Use Drawing Needles: Instructions for Use — 980297 Rev.06, June 2025. PDF p. 1: Needle gauge selection; Gauge Recommendations.
- Greiner VACUETTE Multiple Use Drawing Needles: ROW catalogue — Live, undated. 20G, 21G and 22G entries; items 450061–450063, 450071–450073 and 450075–450077; veterinary-only 18G entries.
- Greiner VACUETTE 21G × 1 inch, item 450072 — Live, undated. Product name and description: 21G × 1 inch, green; 0.8 × 25 mm.
- Greiner Bio-One: Needles—More than just a piece of metal — PIENN01 Rev.00; header reads “September 20”. PDF pp. 1–2: Needle Gauge; wall construction.
- BD Vacutainer Push Button Blood Collection Set: Instructions for Use — VDP40508(01), July 2023. PDF p. 1: gauge-selection table, 25G footnote, Table 1 priming volumes and transfer-device warning; p. 2: Precaution 8.
- BD UltraTouch technical brochure: reference table — BD-59003; copyright 2023. PDF p. 4: reference table, including items 368689, 368688 and 368687.
- BD UltraTouch Push Button Blood Collection Set, 21G, item 368689 — Live US specification, undated. Product title and Product Basic Specification: gauge, needle length, tubing length, wing colour, wall type and priming volume.
- BD UltraTouch Push Button Blood Collection Set, 23G, item 368688 — Live US specification, undated. Product title and Product Basic Specification: gauge, needle length, tubing length, wing colour, wall type and priming volume.
- BD UltraTouch Push Button Blood Collection Set, 25G, item 368687 — Live US specification, undated. Product title and Product Basic Specification: gauge, needle length, tubing length, wing colour, wall type and priming volume.
- Greiner VACUETTE EVOPROTECT 25G, item 450132 — Live Belgium catalogue, undated. Product name and description: 25G × ¾ inch, 12 inch/30cm tubing, orange.
- Greiner VACUETTE EVOPROTECT brochure — 980646 en-US Rev.02, July 2025. PDF p. 6 / printed pp. 10–11: Product Overview, especially 450132.
- BD Vacutainer Eclipse Blood Collection Needle family — Live US page, undated. Product listings: 21G green shield and 22G black shield, 1.25 inch.
- BD Microtainer Contact-Activated Lancet, item 366593 — Live US specification, undated. Overview: fingerstick collection; specifications and FAQ: 21G × 1.8mm, penetration depth.
- BD Order of Draw for Multiple Tube Collections — VS5729-6, November 2010; copyright 2010. Single-page poster: sidebar, winged-set/citrate-first discard note.
- Greiner VACUETTE Blood Collection Tubes: US Instructions for Use — 980200B Rev.09, February 2020; USA only; currently linked from manufacturer catalogue. PDF p. 1: citrate ratio and tube identification; p. 2: Caution 4 on syringe transfer; p. 3: order-of-draw note.
- Greiner VACUETTE Venous Blood Collection: international Instructions for Use — 980200 Rev.24, May 2022. PDF p. 1: cap-colour variation; p. 3: syringe-transfer warning; p. 4: winged-set discard note.
Guidance, standards and exam scope
- WHO Best Practices for Injections and Related Procedures Toolkit, Table 3.3 — 2010. Table 3.3: Recommended needle gauge, length and device for routine injection and phlebotomy procedures.
- WHO Best Practices Toolkit, chapter 3: Best practice in phlebotomy and blood collection — 2010. Sections 3.2.3 (gauge selection) and 3.3.4 (venepuncture for donation).
- WHO Guidelines on Drawing Blood: Introduction — 2010. Section 1.1.1: specimen-quality factors and causes of haemolysis.
- CLSI PRE02: Collection of Diagnostic Venous Blood Specimens — Eighth edition, published February 13, 2025. Edition, publication date and former document code fields.
- CLSI PRE02-Ed8 free sample — Eighth edition, 2025. PDF p. 2: title page “Replaces CLSI GP41-Ed7”; foreword identifies seventh edition as 2017.
- ISO 6009:2016: Hypodermic needles for single use—Colour coding for identification — Fourth edition, August 2016; listing records confirmation in 2021. Official abstract and edition/status fields.
- ISO 9626:2016: Stainless steel needle tubing for manufacture of medical devices — Second edition, 2016; listing says to be revised. Official abstract and status fields.
- NHA Certified Phlebotomy Technician test plan — Based on 2024 job analysis; exam launched January 7, 2026. PDF p. 5: Domain 3, Routine Blood Collections; k55 and k56.
- NHA CPT exam-update FAQ — 2025–2026 CPT transition FAQ. PDF p. 1: When does the new CPT exam launch?.
- NIST Guide to the SI, Appendix B.8 — SP 811 online conversion table; live page. Section I: inch (in) to centimetre and metre.
Research and historical commentary
- Kirchhoff et al. Comparison of a novel thin-walled 25-gauge needle… — J Appl Lab Med. 2023;8(2):264–271. DOI 10.1093/jalm/jfac129. PubMed abstract: Methods, Results and Conclusions; affiliations and grant record.
- Mouser et al. Evaluation of pain and specimen quality… — J Appl Lab Med. 2017;2(2):201–210. DOI 10.1373/jalm.2017.023564. PubMed abstract: specimen-quality study; author affiliations.
- Mayo Clinic Laboratories: Top Gun Phlebotomy—Butterfly Use — February 17, 2020; educational activity lists expiry February 17, 2026. Brad Karon transcript: historical GP41 “any” versus “some” 25G wording.
Written by the Castleport Test Prep Editorial Team. Last verified: September 14, 2026 — the linked device specifications and instructions, dated WHO guidance, standards publication records, NHA topic/date references and published research abstracts were checked. Found an error? Corrections are published and dated.
This resource was developed with AI assistance. See our editorial standards.
Castleport Test Prep is an independent publisher of exam preparation materials. We are not affiliated with, endorsed by, or approved by the Clinical and Laboratory Standards Institute, the World Health Organization, the International Organization for Standardization, Becton, Dickinson and Company, Greiner Bio-One, the National Healthcareer Association, or any certifying body, licensing board or device manufacturer. Product, standard, exam and credential names are used descriptively to identify what is discussed, and trademarks belong to their respective owners.
This is a study and reference resource. It is not a procedure manual and not medical advice. Needle selection for an actual patient is governed by the Instructions for Use for the device in your hand, your facility's written procedure, and your own supervised training.