If you’re blessed enough that you haven’t had blood drawn in a while, you might not have thought much about the process. You might imagine that a needle goes in, a syringe is drawn back, and the venous blood is thusly collected. Indeed, it can be done that way.
However, there is an altogether niftier and more efficient method of fast blood collection for pathology testing. It’s all about using vacuum and smart design to ease the work of phlebotomists, while maintaining a sterile and safe environment.
Vacuum, Contained
These days, if you get blood collected for testing, there’s a plenty good chance you’ll have it drawn into a vacutainer. It’s named as a portmanteau of “vacuum” and “container” because that’s fundamentally what the system relies upon. A vacutainer is a glass or plastic tube which holds a vacuum inside, sealed with a stopper. That vacuum can be used to help extract fluids to be stored inside the container—namely, blood, in most cases.
The method of use is relatively straightforward. A vacutainer needle is inserted into a patient’s vein to access the blood. The vacutainer needle does not have a typical syringe draw. Instead, the back end of the needle sits inside a plastic housing which accepts vacutainer tubes. There is a flexible rubber seal on the back end of the needle so blood doesn’t leak out when no tube is connected.
When a vacutainer tube is inserted into the housing, the vacutainer needle pierces the stopper of the tube. The vacuum inside then draws blood from the vein into the tube for collection. When full, the tube can be removed and it self-seals as the needle comes out of the stopper. Another tube can be quickly clipped into the vacutainer needle housing to draw further blood if more is needed, without leaks or mess causing contamination issues.
Vacutainer tubes are, by design, single use. They’re manufactured to capture a set quantity of blood for testing, based on the level of vacuum in the tube at the time it is sealed, and are disposed of after use. Labels are often included on the tubes allowing patient information to stay with the blood itself. Tubes have a shelf life, as with most medical paraphernalia, in particular since they may not maintain vacuum indefinitely.
The tubes are also typically filled with various additives in order to best preserve and prepare the blood while it awaits testing, and stoppers are color-coded to indicate this. The precise additives used are highly dependent on the testing required. A tube for a standard blood culture draw will typically be filled with sodium polyanethol sulfonate, which acts as an anti-coagulant, with growth media also present for microorganisms.
Coagulation tests will use tubes with sodium citrate inside, while a test for lead will often use a tube with sodium EDTA chelator inside. Some basic blood component tests will use a plain tube with no additives, while others are highly specific—tuberculosis testing often uses purpose-made tubes with antigen additives ready to go. Some tubes include special serum-separating agents which help with splitting blood into its component parts when shaken or centrifuged, useful for certain tests that look at different blood cell types individually.
A package of vacuum blood draw tubes, with the purple cap indicating K2 EDTA additives inside. Credit: via Amazon
" data-large-file="https://hackaday.com/wp-content/uploads/2026/08/71afZqDCscL._SL1500_-1.jpg?w=625" class="size-medium wp-image-1139627" alt="" width="400" height="400" srcset="https://i2.wp.com/hackaday.com/wp-content/uploads/2026/08/71afZqDCscL._SL1500_-1.jpg 1500w, https://hackaday.com/wp-content/uploads/2026/08/71afZqDCscL._SL1500_-1.jpg?resize=250%2C250+250w%2C+https%3A%2F%2Fhackaday.com%2Fwp-content%2Fuploads%2F2026%2F08%2F71afZqDCscL._SL1500_-1.jpg%3Fresize%3D400%2C400+400w%2C+https%3A%2F%2Fhackaday.com%2Fwp-content%2Fuploads%2F2026%2F08%2F71afZqDCscL._SL1500_-1.jpg%3Fresize%3D625%2C625+625w&ssl=1" sizes="auto, (max-width: 400px) 100vw, 400px"/>A vacutainer needle hooked up to a housing. The needle inside the housing typically has a rubber sheath which stops blood flow when no tube is inserted. This allows tubes to be hot-swapped for drawing multiple quantities of blood from a patient. Credit: via Amazon
" data-large-file="https://hackaday.com/wp-content/uploads/2026/08/31ndnPideIL._SX522_.jpg?w=522" class="size-medium wp-image-1139626" alt="" width="400" height="228" srcset="https://i2.wp.com/hackaday.com/wp-content/uploads/2026/08/31ndnPideIL._SX522_.jpg 522w, https://hackaday.com/wp-content/uploads/2026/08/31ndnPideIL._SX522_.jpg?resize=250%2C142+250w%2C+https%3A%2F%2Fhackaday.com%2Fwp-content%2Fuploads%2F2026%2F08%2F31ndnPideIL._SX522_.jpg%3Fresize%3D400%2C228+400w&ssl=1" sizes="auto, (max-width: 400px) 100vw, 400px"/>If you’ve ever dared to watch while having your blood drawn in this manner, the technology can look quite swish. The tubes are easy to hotswap without leaking any blood and several tubes can be filled in under a minute once the phlebotomist has found an appropriate vein.
However, the technology is not particularly new. It was developed all the way back in 1947 by Joseph Kleiner, though other vacuum-based blood draw techniques existed previously. His goal in developing the technology was to ease patient discomfort and reduce the spillage of blood. This stemmed from his experience seeing his terminally-ill wife suffer multiple needle punctures whenever multiple blood tests were required, and seeing the mess caused when syringes were emptied into test tubes for processing and testing. His inspiration was seeing vacuum-sealed tubes used by the military to transport blood during World War II; the product he developed would later reach the market in 1949. They had the benefit of keeping the blood from exposure to air, reduced the number of punctures required along with the chance of needle stick injuries and infection, and ensured blood was collected in standard volumes and conditions, which aided clinical accuracy. Plastic versions were developed by medical supplier Becton Dickinson in the 1960s, and have become widely popular in the phlebotomy field since.
If you’re not in the medical field, and you’ve managed to avoid regular blood tests, you probably haven’t even noticed vacutainers. Alternatively, you might simply live in an area where their use is uncommon, or you’ve just been intently looking away while your blood has been drawn. In any case, they remain a neat little bit of technology that makes a messy, hazardous, medical process as clean and tidy as possible.
Featured image: “Drawing Test tubes different colors” by [Goldmund100].