Written and maintained by CASRAI Editorial Board
Last updated
This page describes products and general use; it is not medical advice.
A red top tube is a blood collection tube used to collect serum, and in the BD Vacutainer range its red closure marks a tube whose inner wall is coated with a clot activator. This guide shows what that coating is, how it differs from orange-closure and gel serum tubes, and which sizes BD publishes. It is written for clinic staff, buyers and students who need to read a tube label correctly.
What is in a red top tube?
In BD’s published range, a standard red Hemogard closure tube carries a silicone-coated clot activator, not a liquid additive. BD’s listing for its Vacutainer serum tube (catalog 367812) gives the additive as “Clot activator, silicone coated” with a red Hemogard closure (BD product page, checked 2026-10-30). BD states that serum tubes are coated with silicone and micronized silica particles to accelerate clotting, and that the silicone coating reduces red cells adhering to the tube wall.
Who uses it: phlebotomists and laboratory staff who collect serum for testing, and the buyers who stock those tubes. Colour conventions differ between manufacturers, so the tube’s own label and the manufacturer’s instructions for use decide what a given closure means.
How is the tube built?
BD’s Vacutainer Plus serum tubes are plastic. The BD product page lists the glass-or-plastic field as plastic and states they are made of a special formulation of polyethylene terephthalate (PET). The tube is evacuated, closed with a Hemogard closure and carries a paper label. The silica coating can sometimes make the inner wall look cloudy or filmy; BD notes this on its product page as something that can occur.
Red vs orange vs red/gray: which serum tube is which?
The red closure is one of several serum tubes in BD’s range. The table compares three BD products; it describes BD products only and does not rank them.
| Tube (BD catalog no.) | Closure | Additive as listed by BD | Key difference |
|---|---|---|---|
| Vacutainer serum tube (367812, 367814) | Red Hemogard | Clot activator, silicone coated | No gel; plastic (PET) |
| Rapid Serum Tube (368774) | Orange Hemogard | Thrombin-based clot activator | Different activator from the red tube; orange is not red |
| SST tube (367987) | Conventional red/gray | Clot activator with double polymer gel (transport tube) | Contains gel between the clot and serum layers |
Sources: BD product pages 367812, 368774 and 367987 on bd.com, checked 2026-10-30.
What sizes does BD publish?
| BD catalog no. | Draw volume | Tube size | Material |
|---|---|---|---|
| 367812 | 4 mL | 13 x 75 mm | Plastic |
| 367814 | 5 mL | 13 x 100 mm | Plastic |
BD publishes different centrifugation guidance for non-gel serum tubes and for gel tubes, so the exact catalog number and its electronic instructions for use (eIFU) matter. Follow the instructions for use packed with the lot you hold. To understand the equipment itself, see what a centrifuge is, and for the wider colour system see blood draw tube colors.
Sources: BD product pages 367812, 367814 and 367987, checked 2026-10-30.
Why does the coagulation caveat matter for order of draw?
Order of draw is set by your laboratory’s collection procedure and the tube manufacturer’s instructions, and the position of clot-activator serum tubes relative to the light blue citrate (coagulation) tube is part of it. Follow your own procedure rather than this page. See also the blue top tube additive and gray top tube additive guides for neighbouring tubes.
Common mistakes
- Treating every red closure as the same product. BD’s red/gray SST tube contains gel and an orange closure marks a thrombin-based activator, so check the label and catalog number.
- Applying guidance for a gel tube to a non-gel tube from memory instead of the instructions for the tube in hand; BD lists different guidance for each.
- Reading a cloudy inner wall as a defect; BD notes the silica coating can cause this appearance and that it does not make the tubes unacceptable for use.
- Ignoring your laboratory’s order-of-draw procedure when a clot-activator tube and a coagulation tube are drawn together.
Frequently asked questions
What additive is in a red top tube?
For BD’s standard red Hemogard serum tube, the listed additive is a silicone-coated clot activator (silica particles on the wall). Other manufacturers may differ, so read the label.
Is a red top tube made of glass or plastic?
BD’s Vacutainer Plus serum tubes (367812 and 367814) are plastic, made of PET. This page makes no claim about other brands or older glass tubes.
Is orange the same as red?
No. BD’s orange-closure Rapid Serum Tube uses a thrombin-based clot activator, while the red closure tube uses a silicone-coated clot activator.
Where can I read about the other supplies around tube collection?
The phlebotomy lab supply checklist covers the wider supplies around tube collection.
Sources
- BD Vacutainer serum tubes, catalog 367812: https://www.bd.com/en-us/products-and-solutions/products/product-page.367812 (checked 2026-10-30)
- BD serum tube, catalog 367814: https://www.bd.com/fr-ca/products-and-solutions/products/product-page.367814 (checked 2026-10-30)
- BD Rapid Serum Tube, catalog 368774: https://www.bd.com/en-us/products-and-solutions/products/product-page.368774 (checked 2026-10-30)
- BD SST tube, catalog 367987: https://www.bd.com/en-us/products-and-solutions/products/product-page.367987 (checked 2026-10-30)
