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.