What color tube is used for a CBC?

Lavender (purple) — it contains EDTA, the anticoagulant used for CBC and most hematology.

What tube is used for PT/INR?

Light blue — it contains sodium citrate for coagulation testing, and it needs to be filled to the line.

What's the difference between a red tube and a gold/SST tube?

Both give serum. A gold/SST tube adds a clot activator and a gel that separates the serum from the cells when spun; a plain red tube has no gel. Your lab's directory says which to use.

Blood collection tube colors: what each one is for

A blood tube's cap color tells you its additive, and the additive tells you which tests it's for. Light blue is citrate (coagulation), red is plain serum, gold/SST is serum with a gel separator, green is heparin (plasma chemistry), lavender is EDTA (CBC), and gray is fluoride/oxalate (glucose).

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The Test and Tube reference in Phlebotomy Toolkit listing CBC (lavender, EDTA), CMP (gold or light green, SST), PT/INR (light blue, sodium citrate), and Blood Culture, each with a color-coded tube icon

Color → additive → what it's for

Light blue — sodium citrate — coagulation studies (PT/INR, aPTT). Fill to the line; the blood-to-additive ratio matters.
Red — no additive (or a clot activator in plastic tubes) — serum for many chemistry, serology, and blood-bank tests.
Gold / SST ("tiger top") — clot activator + gel separator — serum chemistry; the gel separates serum from cells after spinning.
Green — heparin (lithium or sodium) — plasma chemistry, stat chemistries, and ammonia.
Lavender / purple — EDTA — CBC and most hematology; also HbA1c.
Gray — sodium fluoride + potassium oxalate — glucose and lactate (fluoride preserves glucose).
Yellow — two kinds: SPS for blood cultures, or ACD for DNA/HLA testing.

Exact tube choices, brands, and any facility-specific rules live in your laboratory's test directory.

Which tube for common tests

CBC → lavender (EDTA).
CMP / BMP → gold/SST (serum) — or green (lithium heparin) at some labs.
PT/INR → light blue (sodium citrate).
HbA1c → lavender (EDTA) at many labs.
Glucose (preserved) → gray (fluoride/oxalate).

When a test could go in more than one tube, your lab's directory decides — check it.

Handling & inversions

Additive tubes need gentle inversions right after they fill so the additive mixes and the specimen doesn't clot — but the number of inversions varies by tube type and manufacturer. Follow each tube's instructions for use and your facility's guidance; don't shake.

See every tube in the app

Phlebotomy Toolkit's Test & Tube reference shows each test's tube color, additive, handling, inversions, and common rejection risks — searchable and offline.

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FAQ

What color tube is used for a CBC?
Lavender (purple) — it contains EDTA, the anticoagulant used for CBC and most hematology.
What tube is used for PT/INR?
Light blue — it contains sodium citrate for coagulation testing, and it needs to be filled to the line.
What's the difference between a red tube and a gold/SST tube?
Both give serum. A gold/SST tube adds a clot activator and a gel that separates the serum from the cells when spun; a plain red tube has no gel. Your lab's directory says which to use.