How Does A Blood Test Work?

Blood tests are expected in a doctor’s office, and most of us don’t even realize we are getting one until the needle pricks our skin. But how does this simple, often-painless procedure give so much information to the medical staff? Let’s take a look at how blood tests work to find out!

What Happens During The Test

Once blood is drawn, it goes through a small tube which is spun very quickly to create plasma. The blood also is mixed with an anticoagulant (added to keep it from clotting during testing) before being spun down. The spinning causes proteins and other molecules in your blood to band together into various size particles, allowing them to be separated by weight and identified easily. Each particle is then identified and counted, providing insight into what’s going on inside your body at that time. While some tests measure direct results of certain conditions, others simply identify deficiencies or excesses of elements such as calcium or magnesium that can lead to serious health problems if they remain out of balance for too long.

What Information Is Obtained


Every blood test is different, but most provide a wealth of information about your body. For example, you may be tested for anemia, which refers to a reduced number of red blood cells or hemoglobin. Hemoglobin is responsible for carrying oxygen from your lungs to tissues throughout your body. Low levels may result in shortness of breath and fatigue. People who are menstruating can have anemia due to excessive blood loss. The good news is that symptoms can be easily treated with supplements such as vitamin B12 or iron. If severe, however, anemia can lead to heart failure and even death.

Another common blood test measures your cholesterol levels by determining how much high-density lipoprotein (HDL), low-density lipoprotein (LDL), and triglycerides (blood fats) you have. High HDL has been linked to a lowered risk of heart disease, while high LDL has been associated with plaque buildup within arteries leading to coronary artery disease or stroke. High triglycerides correlate with high LDL levels as well as diabetes and obesity. Together these numbers create your lipid panel. All of these results give doctors a valuable insight into your overall health and risk factors for developing certain conditions. When undergoing a diagnostic workup based on symptoms, it’s best not to do it during fasting periods since not eating affects what kind of lab tests will be drawn.

When you have an illness, your doctor may prescribe a blood test to determine what’s causing it, which can help determine which course of treatment would be most effective. Blood tests are low risk: some common complications of blood tests include bruising and infection. Despite these risks, doctors use blood tests regularly because they help them understand what’s going on inside your body—and that knowledge could save your life.