Behind the Scenes of Blood Testing

By Katya Margolin, July 21, 2023


Blood testing is what health tracking devices always wanted to be.

They all show you aspects of what's happening in your body so you could make better lifestyle choices to be healthier, but blood testing tells a deeper story than a mobile app or wristband could tell on their own. With all these devices and services becoming more accessible, healthcare is finally shifting from your doctor's hands to your own, and advancements in blood testing are opening even greater doors. 

Most of us have had our blood drawn at some point, whether it was a doctor's appointment or a donation with the Red Cross, so you probably have a general idea of how it goes down. But, have you wondered what happens from the moment the needle pricks your arm to the time you get your results in the mail?

Turns out, it is an intricate process. Blood needs to be collected, stored, packaged, transported, and analyzed with very particular, nuanced methods. Read on to learn everything you never realized you wanted to know about the wonderful complexity of blood testing. 

What is Blood Testing?

Blood tests reveal how our health is doing by showing what is in our blood. That deep red fluid is packed with different substances, like proteins, nutrients, and hormones. Analyzing them requires a fresh blood sample, a very careful and sterile process, and fancy tools and machinery at specialized labs. Giving a blood sample normally takes less than 3 minutes (1) and is painless, though some people may experience temporary discomfort and bruising from the needle shortly after the blood draw (2).

Why Get Blood Tests?

Blood tests can uncover the risk or development of health problems that would otherwise go unnoticed. This is crucial for preventing disease or stopping it in its tracks. If you use any medication, blood tests also let you know how well treatments are working (3).

Tracking disease is important, but did you know blood tests could also track the quality of your health?  

Track Health, Not Just Disease

Traditionally, we get blood tests once a year during our annual physical exam. These tests are generic and focus on a limited set of biomarkers related to disease, while falling short on assessing your health. This is no longer good enough.


"Healthy" has a broad spectrum; you don't have to be sick to be set back. Even if you are free of disease, you might still feel tired, unfocused, slowed down, plateaued, or burdened with a few extra pounds more often than you'd like. That's because you're not optimized. InsideTracker looks at biomarkers related to physical and cognitive health and performance to assess whether your blood levels are optimal, rather than just normal, so you can achieve your best potential. It all starts with your blood sample. 


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Blood Basics                                                                    

There are 5 liters of blood circulating throughout the human body at all times, keeping us alive and functioning properly. Blood provides oxygen and nutrients to tissue, and removes waste. Approximately 45% of our blood consists of red blood cells, less than 1% consists of white cells and platelets, and the remaining 55% is made up of clear yellowish fluid called plasma (4).

Each substance has a unique, essential role:

Plasma nourishes tissues: Plasma is a liquid in your blood that transports water and nutrients to the body’s tissues (5).

  • 92% percent of plasma consists of water (4)
  • 7% contains proteins, like antibodies and clotting factors
  • ~1% consists of hormones like insulin, nutrients like sugar, and electrolytes like sodium.

Red blood cells carry oxygen: Red blood cells contain the protein hemoglobin, which carries oxygen throughout the body and removes carbon dioxide from tissues. 

White cells fight infection: White blood cells are part of your immune system and defend the body by fighting infection.

Platelets control blood clotting: Platelets are smaller blood cells that help your blood clot. They end bleeding by sealing cuts on blood vessel walls (6).

There are many different types of tests and procedures to analyze the various substances in blood. The right preparation for your blood draw depends on what is being tested. 

Preparing for Your Blood Test

While some tests do not need any special preparation, other blood tests—including the ones we conduct at InsideTracker—require fasting for 12 hours before your blood draw. A blood sample from a fasting state better represents your natural, baseline blood levels. Substances from food temporarily change your blood levels and can interfere with analyses (7), so a sample taken in a non-fasting state may render misleading results.

Exercise also alters your blood levels, so you shouldn't partake in any exercise or unusual physical activity during the 24 hours before the draw unless you are specifically testing how this activity affects you.


For your blood draw with InsideTracker, you will go to a Quest Diagnostics Patient Service Center, unless you ordered an at-home test. We recommend drinking a lot of water during the 24 hours before your test as this will help the blood to flow more freely during the blood draw. Remember to bring a printed copy of your InsideTracker lab slip to the blood draw as your examiner will need this to know how to take your blood samples.

Out of the 5 liters of blood in your body, even 3-5 full vials are a safe quantity and unsubstantial, so don't worry! This ensures that enough samples are available for back-up in case some samples are compromised. It also allows for any confirmatory tests that may be needed after the initial tests.

Preparing Blood for Analyses

Your blood samples must be handled very precisely to maintain their integrity and protect the blood analyst from any possible infection. Lab technicians and everyone else who handle the samples follow specific guidelines to avoid contaminating the samples, keep cells alive, and prevent too much from changing, which happens naturally the longer the blood is removed from its host. There's even a method to proper labeling so your blood samples are tracked securely while keeping your personal information private.

Proper handling of the blood sample starts with choosing the right test tube to contain it; there are various types of tubes designed for specific types of tests. Tubes are capped with a vacuum seal so, if the cap is punctured with a special needle to collect blood, the pressure effortlessly pushes blood into the needle without risking contamination.


For certain tests, it is important that blood does not clot. In these cases, the samples go in test tubes lined with Ethylenediaminetetraacetic acid (EDTA), a chemical that prevents clotting.  

Blood samples also need to be kept at the right temperature, which will vary according to what is being tested. Storage temperature usually ranges between room temperature (15 - 30°C), refrigerated (2 to 10°C), or frozen (-20°C or colder) (7).

Specific components of the blood may need to be isolated for certain tests. In these cases, whole blood needs to be separated into its three main components: plasma, white blood cells and platelets, and red blood cells. This separation is achieved through centrifugation, the method of separating lighter and denser portions of a mixture by centrifugal force. If the tests call for it, the test tube with your blood sample will be placed in a device called a "centrifuge." This device spins very quickly to separate heavy and lighter components of the blood. After centrifugation, you can see the blood separated into three layers. The lighter components (plasma) naturally end up on top. Specific components of the blood can now be isolated, transferred into another container, and analyzed individually.

Transferring blood components is also a delicate process. Biosafety practices have been established to protect blood samples and the people handling them. To prevent contamination, test tubes typically should be opened in a biological safety cabinet (BSC), or biosafety cabinet, —an enclosed and ventilated desk space designed for working with materials that have the potential to contaminate or be contaminated with pathogens. There are three types of biosafety cabinets for different types of tests. Air circulates in these cabinets as it flows from the bottom and gets sucked up at the top, so no air can enter or escape. This protects the interior of the cabinet from external contaminators and prevents any pathogens from escaping the cabinet.

A Long Journey

Once the blood samples have been centrifuged and transferred to a proper container, as needed, they are transported to a regional lab for analysis. This can be quite a journey; the samples are driven by car to an airport, flown to another city—possibly traveling hundreds of miles—and driven again to their final destination. As you can imagine, the commute will expose blood samples to all sorts of bumps, shocks, and temperature fluctuations, so proper packaging is essential to keep the blood samples secure. 

Packaging blood samples for transport may involve details like using the right containers, tight caps and lids, special transport bags and boxes, and proper labels and seals. Frozen samples should be transported in plastic -screw-cap containers only, and will be shipped with ice to remain frozen until they reach the laboratory (7). This is important because analysis cannot be done on thawed samples. Dry ice is used for longer distances. Transporting by air comes with a long list of packing policies created by the International Air Transport Association (IATA), the trade association for the world’s airlines that helps formulate industry policy on critical aviation issues, like the safe transport of sensitive goods.

As you can see, a lot goes into just moving blood samples across locations. When ready, your InsideTracker blood sample will be transported from the Quest Diagnostics Patient Service Center to a Quest Diagnostics lab to be analyzed. All Quest labs are certified in Clinical Laboratory Improvement Amendments (CLIA), which ensures quality standards for laboratory testing.

Analyzing Blood

Different tests are designed to analyze various components of your blood and assess certain aspects of your health. Whole blood is used to count red blood cells, while plasma is separated from blood cells by centrifugation to undergo other tests (3). Some tests require serum, which is what remains in place of plasma after blood clots so no clotting factors are present. Blood is left to clot for sixty minutes and then centrifuged for 15 minutes to separate the serum (8).


Plasma is more commonly used for tests because its components are believed to better reflect a patient's pathological situation than those in serum (9). For these analyses, test tubes are lined with the chemical anticoagulant EDTA to prevent clotting.

Now What?

Blood test results are generally available in three to seven days, depending on which markers are being tested. If you had a standard blood test at your doctor's and no signs of disease were found, then there are no next steps. Once InsideTracker gets your results, however, we invite you to start a new chapter. We incorporate your results with our evidence-based algorithm to make recommendations for optimizing your health. These are practical steps you can take each day to feel, perform, and live better. The efficacy of each intervention we recommend is substantiated by multiple credible sources from our cited database. These recommendations are customized for each individual depending on your need, goals, and lifestyle preferences, while keeping your personal information secure and private.


If you're tracking your steps or sleeping patterns, shouldn't you be tracking what's in your blood just as consistently?

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  1. "What to Expect with Blood Tests." National Heart, Lung, and Blood Institute. National Institutes of Health, 6 Jan 2012. 21 May 2015.
  2. "What Are the Risks of Blood Tests?" National Heart, Lung, and Blood Institute. National Institutes of Health, 6 Jan 2012. 21 May 2015.
  3. "What are blood tests?"National Heart, Lung, and Blood Institute. National Institutes of Health, 6 Jan 2012. 21 May 2015.
  4. "Blood Components." American Red Cross. The American National Red Cross, 2015. 21 May 2015.
  5. "Blood Basics." American Society of Hematology. American Society of Hematology, 2015. 21 May 2015.
  6. "Types of Blood Tests." National Heart, Lung, and Blood Institute. National Institutes of Health, 6 Jan 2012. 21 May 2015.
  7. "General Guidelines." Quest Diagnostics. Quest Diagnostics. N.d. 23 May 2015.
  8. "SERUM, PLASMA OR WHOLE BLOOD COLLECTION." Quest Diagnostics. Quest Diagnostics. N.d. 23 May 2015.
  9. "Blood samples: whole blood, serum, plasma." HSeT Foundation. HSeT Foundation, 1 Nov 2012. 23 May 2015.

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