This article was last reviewed on
This article waslast modified on January 28, 2021.

Ever wonder what happens to your blood sample once it's been collected? It's sent "to the lab" for analysis, but what does that entail? This article will take you on a tour as a blood sample is processed.

In the laboratory, trained laboratorians use various methods to analyze your sample as determined by what types of tests you need performed. The Who's Who in the Lab article introduces you to these lab personnel.

For every test, there is an appropriate sample that provides the best information for that test. To learn about other types of body samples besides blood and throat swabs that can be collected for analysis, see the article Collecting Samples for Testing.

Accordion Title
The Steps
  • Collecting blood

    Depending on the facility where you have your blood drawn, a doctor, nurse, phlebotomist or other laboratorian, or another medical professional will draw your blood. In this picture, a phlebotomist has inserted a needle into a vein on the outer portion of the arm near the elbow.

    When multiple tests are ordered, more than one tube of blood may be collected, and there is a specific order in which different collection tubes with special preservatives must be drawn.

  • Labeling the blood sample

    Once the blood is drawn, the tube is labeled. In many labs, the label may be pre-printed with the patient's name and unique patient identification number, or a barcoded label carrying this information is used. It is essential that the person drawing the sample label the tube properly before leaving your side.

  • Documentation

    After the sample has been collected and labeled, it is transported to the lab to be logged in. Depending on the test needed and where you have the sample drawn, your blood may be simply transported to the lab where the analysis is performed or transported to a lab that specializes in a particular blood analysis.

    Once the specimen arrives in the lab, however near or far away, your blood sample will be logged into the laboratory's tracking system. The tube label contains all the information necessary to ensure that the sample is analyzed for the appropriate tests and the results are matched to your name. Usually, a written or electronic requisition form listing not only your information but also your health practitioner's name and address is sent with the sample so the results can be sent to the appropriate person.

  • Processing

    Depending upon the tests that have been ordered, your blood sample may be processed before it is analyzed. Most routine laboratory tests are performed on either plasma or serum. Plasma is the liquid portion of blood. It is separated from the cellular portion of blood by rapidly spinning the specimen in a centrifuge for several minutes. The plasma, which has a light yellow color, appears at the top of the tube, while the blood cells are at the bottom.

    Serum is plasma that has been allowed to clot. It is prepared in the same way as plasma; however, the blood is collected into a tube with no anticoagulant. While spinning in the centrifuge, the clot moves with the cells to the bottom of the blood collection tube, leaving the serum on top.

    If the test requires whole blood (e.g., a complete blood count), the sample can be analyzed directly without further processing.

  • Testing (automated)

    In most cases, an instrument, appropriately called a blood analyzer, analyzes the blood sample. In this picture, the tube of blood is being placed directly into the machine. This particular state-of-the-art analyzer is capable of running batches of samples -- up to 120 samples per hour. In general, chemistry analyzers use serum and/or plasma, and hematology and coagulation analyzers use blood that contains an anticoagulant to prevent clotting. 

  • Results

    With the latest technology in analyzers comes the ability to generate the results electronically and graphically. In this case, the results will be sent electronically to the health practitioner. In many situations, results are printed and then faxed. If the results indicate that the patient may be very ill, the laboratory will call the health practitioner with the results and then send the written or electronic report.

    The length of time between the drawing of the blood and when the health practitioner gets the results can vary greatly, from as little as a few minutes to as much as several weeks. Urgency, geographic distances, processing schedules, complexity of the test, and other factors contribute to the length of time required before results are available to the health practitioner, who will then share the results with you, the patient.