Royal Blue Top Tube
Trace-element-free (EDTA or no additive)
Royal blue is the specialty tube most phlebotomists draw rarely and remember badly. Trace-element-free glass and stoppers, made specifically so that the tube itself does not leach detectable amounts of metal into the sample. If the test is heavy metals or trace nutrients, royal blue is the only acceptable choice.
The additive.
There are two royal blue variants. The EDTA royal blue contains the same K2 or K3 EDTA as a lavender top, but the tube glass and stopper are manufactured to be trace-element-free. This is for whole-blood lead, mercury, and similar tests where EDTA is needed and trace contamination would be detected.
The plain (no-additive) royal blue is essentially a trace-element-free version of a plain red. Used when serum is needed and trace metal contamination would alter the result.
A standard plastic tube leaches micro-amounts of zinc, lead, and other elements into the sample. For a CBC that does not matter. For a lead level reported in micrograms per deciliter, that contamination becomes the result. Royal blue glass is manufactured to a different standard.
What the royal blue top is used for.
Whole-blood lead screening for public health programs and pediatric workups. The test is reported in mcg/dL and even small contamination distorts the result.
Trace metals: zinc, copper, manganese, selenium, mercury, arsenic. Used in occupational health screening, nutrition workups, and toxicology.
Trace nutrient panels: chromium, molybdenum, and other micronutrients. Often part of a wider workup for unexplained fatigue or specific clinical syndromes.
How to draw it correctly.
Draw 7 mL. Royal blue tubes are typically a single fixed size; check the manufacturer for variants.
Invert 8 to 10 times if the tube is the EDTA variant. Zero inversions for the plain variant (it functions like a plain red).
Ordering matters. The EDTA royal blue follows lavender logic and falls at CLSI position 5. The plain royal blue follows serum logic and falls in position 3 with red and gold. The cap color alone does not tell you the position; always confirm the additive.
Three mistakes that cost you a recollect.
- 1
Confusing EDTA royal blue with plain royal blue
Different draw position, different inversion count, different downstream handling. The cap color is identical; the additive is everything.
- 2
Drawing into the wrong tube for trace metals
A lavender or a green can contaminate the sample with trace zinc or lead from the manufacturing process. The result reads as elevated when the patient is fine.
- 3
Treating royal blue like light blue
They look similar. They are not. Light blue is sodium citrate for coagulation; royal blue is trace-element-free glass for heavy metals. Read the label.
Royal Blue in the order of draw.
Royal blue is the only tube without a fixed CLSI position. EDTA royal blue draws with the lavenders at position 5. Plain royal blue draws with the serum group at position 3. Confirm the additive before deciding when to draw it.
See the full CLSI order-of-draw page →Common questions about the royal blue top.
What is the royal blue tube used for?
Royal blue vs light blue, what is the difference?
Where does royal blue go in the order of draw?
Why use a special tube for lead testing?
Can I use a regular EDTA tube for lead?
Six more tubes you will see on the same tray.
- Lavender Lavender/ PurpleCLSI 5 · EDTA (K2 or K3)
- Light Blue Light BlueCLSI 2 · Sodium citrate 3.2%
- Red RedCLSI 3 · None (glass) or clot activator (plastic)
- Gold Gold/ SSTCLSI 3 · Clot activator + thixotropic gel
- Green GreenCLSI 4 · Lithium or sodium heparin (PST has gel)
- Gray GrayCLSI 6 · Sodium fluoride + potassium oxalate