What Tube for a CBC (complete blood count)?
Lavender-top K2EDTA tube (pink K2EDTA is also accepted).
- Additive
- K2EDTA
- Inversions
- 8–10 times
- Order of draw
- #5 of 6
Collection and handling
- Invert 8–10 times right away so the EDTA mixes and the sample does not clot.
- A clotted CBC sample is rejected; even small clots change the cell counts.
Exam tip
EDTA is drawn after the serum and heparin tubes. EDTA carried into a chemistry tube falsely raises potassium and lowers calcium, which is why order of draw matters.
Where it falls in the order of draw
- 1. Blood culture bottles (aerobic + anaerobic) (Culture media)
- 2. Light blue (3.2% sodium citrate)
- 3. Gold / red-gray (SST) or red (Clot activator (SST also has gel))
- 4. Green / light green (PST) (Lithium heparin (PST also has gel))
- 5. Lavender (or pink) (K2EDTA)
- 6. Gray (Sodium fluoride / potassium oxalate)
Full explanation in the order of draw guide.
Tube requirements differ between labs and assays. Always follow your own laboratory's collection manual.
Drill tubes and order of draw until they stick
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