Amount of Blood Needed for a Blood Test | Arthritis Information

I just had a CBC and CMP blood test. I was so afraid to look while the nurse was taking my blood that I didn't notice that she didn't fully fill the vial until after it was over and she took out the needle from my arm. The vial was only about 3/4 full. Is that enough to get an accurate blood test result?

I was just thinking that it would be so easy for these blood testing companies to just send out any old result without actually performing the tests and consumers like me wouldn't even know that the lab report we get is just a bunch of random numbers.

3/4 of a tube is plenty. It shouldn't be all the way full because you need to allow room for the blood to be agitated. It would not be in the labs best interest to produce bogus reports as a policy. The lawsuit vulnerability would be way too muchThey don't even need that much for the tests you took. Some labs have a policy of taking a little more in case there's an accident with a specimen once it's out of the container OR in case the doctor's office calls as an afterthought and wants to run an additional test.

As a lab technician I can offer some input here. Sam1234 is correct in saying that some labs draw more than needed in case another test is ordered by the doctor later. This saves us from having to poke you again. Also, sometimes things happen and a test may need to be repeated with a diluted specimen so then we have enough to do that as well. For a CBC and CMP there should have been two tubes drawn. One that had a lavender top and one that had a green top. The tubes are color coded according to the additive that is in them. When we run a cbc the machine usually only takes a drop or two of blood for the test. I've done cbc's from a finger stick on children before.

The thing on bogus reports is not only highly illegal but highly immoral and anyone who would do such a thing does not belong in the lab. I can say that I've never fudged any results myself and I don't care how long it takes to get an accurate result or how many times I need to run the test. Also, most labs have what is called LIS which stands for lab information systems that is integrated into the instruments doing the analysis. When the test is done the info is uploaded to the system and the tech must then review the results and release them for the doc to be able to view.

Bob

I agree that 3/4 vial is plenty and that it doesn't hurt to have extra... just in case.

Bob, what interests me is how many vials drawn at one time is too much?

I had 10 drawn once and my niece had 12! I was fine but she got lightheaded.

Is that frequently done?

Most tubes are in a vaccuum and fill to the desired amount unless stopped before hand by either pulling the tube out or by removing the needle for the vein.I've actually drawn more than 12 on a patient before. It was called therapeutic phlebotomy which is used when you actually have too much blood. Yes, this can happen and will force your heart to work harder causing cardiac overload which can kill you obviously.

Wendy. All the tubes are what are called vacutainers and have a small amount of vacuum in them in order to draw in the blood. This is why you will sometimes hear a tech or phlebotomist say that the tube blew out the vein. Sometimes the vacuum is too much for the vein and poof it collapses. Usually this happens on the older folks more often but can happen to anyone really.

Another nice thing I learned is to always disengage the tube before removing the needle. If you dont then blood can backflow from the tube out the needle. Messy...messy...messy way to learn but effective!

Bob