Order of draw
Why blood tubes are filled in a set order, and where to find the order your laboratory uses.
Why order matters
Tubes contain additives. Filling them in the wrong order can carry an additive from one tube into the next and change results. EDTA carried into a biochemistry tube, for example, can affect calcium and potassium results.
A commonly used order
Blood cultures first, then citrate (coagulation), then serum tubes with or without gel, then heparin, then EDTA, then fluoride oxalate. Cap colours vary between manufacturers, so go by the additive, and follow the order your receiving laboratory specifies.
Mixing
Gently invert each tube as the manufacturer instructs. Do not shake tubes; shaking can haemolyse the sample.
General information only. It is not accredited CPD and does not replace your training, your employer's procedures or the receiving laboratory's requirements.
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