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Blood Tube Colors:
The Complete Reference Chart.

Every BD Vacutainer cap color, what is inside it, what it tests, and where it falls in the CLSI order of draw. Built by instructors who got tired of explaining this from a blurry handout.

Jump to chart ↓ Order of draw
02 · The chart

Blood tube colors chart: the seven tubes you will actually draw.

Cap colors below match BD Vacutainer specifications. The CLSI position is the canonical 6-step sequence in section 4.

Lavender

Lavender / Purple

5 CLSI

EDTA (K2 or K3)

CBC ESR Blood bank typing HbA1c
Volume
4–6 mL
Inversions
8–10
immediately after draw
Read the lavender top tube guide →
Light Blue

Light Blue

2 CLSI

Sodium citrate 3.2%

PT PTT INR Fibrinogen D-dimer
Volume
2.7–4.5 mL
Inversions
3–4
immediately after draw
Read the light blue top tube guide →
Red

Red

3 serum group

None (glass) or clot activator (plastic)

Serology Immunology Blood bank crossmatch Drug levels
Volume
6–10 mL
Inversions
0–5
immediately after draw
Read the red top tube guide →
Gold

Gold / SST

3 serum group

Clot activator + thixotropic gel

CMP BMP Lipid panel Hormones Drug levels
Volume
3.5–8.5 mL
Inversions
5
immediately after draw
Read the gold top tube guide →
Green

Green

4 CLSI

Lithium or sodium heparin (PST has gel)

STAT chemistry Ammonia Lactate
Volume
4–10 mL
Inversions
8–10
immediately after draw
Read the green top tube guide →
Gray

Gray

6 last

Sodium fluoride + potassium oxalate

Glucose Lactate Alcohol Glucose tolerance
Volume
2–10 mL
Inversions
8–10
immediately after draw
Read the gray top tube guide →
Royal Blue

Royal Blue

varies 5 or 3 by additive

Trace-element-free (EDTA or no additive)

Lead Zinc Copper Mercury Nutrition panels
Volume
7 mL
Inversions
8–10
immediately after draw
Read the royal blue top tube guide →
03 · Picker

Pick a cap, see the details.

Tap a tube. The detail panel below is the same info you would get on the back of the classroom poster, plus one thing students keep getting wrong.

Lavender/ Purple

EDTA (K2 or K3)

The CBC tube. EDTA chelates calcium so blood cannot clot, and cell morphology stays intact for hours.

5CLSI
CBCESRBlood bank typingHbA1c
Volume
4–6 mL
Inversions
8–10
CLSI position
5
of 6

Common mistake. Invert gently 8 to 10 times right after the draw. Clots in a lavender are an instant recollect.

Read the full lavender top tube guide →
04 · Phlebotomy order of draw

Order of draw: CLSI H3-A6 in six steps.

The order exists because additives migrate. A trace of EDTA in a chemistry tube is enough to trash the calcium and potassium results. Memorize the sequence, then memorize why each step is where it is.

  1. 1
    Blood culture
    Yellow SPS bottle
    Sterile site first. Always.
  2. 2
    Light Blue
    Sodium citrate (coagulation)
    Protected from any tissue thromboplastin.
  3. 3
    Red / Gold
    Serum group (no anticoagulant)
    Either order within the group is acceptable.
  4. 4
    Green
    Heparin (PST)
    Plasma chemistry, before any chelating additives.
  5. 5
    Lavender / Pink
    EDTA
    EDTA carryover ruins downstream chemistry, so it sits late.
  6. 6
    Gray
    Fluoride / oxalate
    LAST. No exceptions. Fluoride and oxalate contaminate anything earlier.
Mnemonics, examples, and exam traps →
05 · Questions

The questions that come up every semester.

What color tube is drawn first?
The yellow SPS blood culture bottle is drawn first whenever cultures are ordered. If no cultures are ordered, the light blue (sodium citrate) tube is first. Drawing it first protects the coagulation tests from any tissue thromboplastin or additive carryover from other tubes.
What color tube is used for a CBC?
A complete blood count goes in a lavender (purple) top. The additive is EDTA, which chelates calcium so the blood cannot clot and cell morphology stays intact for hours. EDTA is also used for ESR, blood bank typing, and HbA1c.
Why is the gray tube last?
Gray contains sodium fluoride and potassium oxalate. Both will contaminate other additives if they carry over, and oxalate damages cell membranes. The gray tube goes last every time, no exceptions, so its additives can never reach an earlier tube.
Light blue vs royal blue, what is the difference?
Light blue is sodium citrate for coagulation testing (PT, PTT, INR). Royal blue is a trace-element-free tube made from special glass and stoppers, used for heavy metals and trace nutrient panels (lead, zinc, copper, mercury). They are not interchangeable, even though they look similar at a glance.
What happens if I underfill a citrate tube?
Light blue tubes have a fixed 9 to 1 blood-to-additive ratio. Underfilling shifts the ratio and falsely prolongs PT and PTT results. Most labs reject any citrate tube under 90 percent of the fill line. Always fill to the indicator.
Why does the order of draw matter?
Tiny amounts of additive can transfer from one tube into the next through the needle or stopper. EDTA carryover into a chemistry tube falsely lowers calcium and elevates potassium. Following CLSI order of draw prevents these errors before they reach the patient chart.
Is the SST the same as the gold top?
Yes. SST stands for serum separator tube. The gold top (sometimes called tiger top with a red and gold marbled cap) contains a clot activator plus a thixotropic gel that forms a barrier between serum and cells after centrifugation.
Do EDTA and lavender mean the same thing?
In day-to-day phlebotomy, yes. The lavender (purple) top is the standard EDTA tube. Pink top tubes also contain EDTA but are reserved for blood bank specimens because of their special labeling requirements.
06 · Free practice

Studying for the NHA CPT?

PhleboPrep offers 10 free practice questions every week. Includes order-of-draw scenarios just like the real exam.

Try free practice →