Tubes are drawn in a specific order to avoid the possibility of erroneous test results caused by carryover of an additive from one tube to the next.
If a blood culture is ordered, it should be drawn as the first tube. Additional tubes should follow this order of draw.
- Sodium citrate - coagulation tube (light-blue top)
- Serum tube - with or without clot activator or gel. This tube is either a red top tube or a gold top tube depending on manufacturer and tube additive.
- Sodium or lithium heparin with or without gel plasma separator (green top)
- Potassium EDTA (lavender or pink top)
- Sodium fluoride, and sodium or potassium oxalate (gray top)