How does blood testing work?

How does blood testing work?

The information presented here does not constitute medical advice, and is not intended to be a substitute for a consultation with your medical doctor.

You’ve likely done a blood test at least once in your life, likely as part of your routine checkup, or before a surgery.

However, if your doctor is anything like ours, they likely never bothered to explain your options, how blood testing actually works, and how to interpret results.

Let’s jump right in!

What is blood?

Blood is a fluid that circulates through our body and delivers essential substances like oxygen and nutrients to the body’s cells.

It also transports metabolic waste away from those cells, detects foreign bodies, delivers messages through hormones and regulates body temperature.

Blood composition changes with diet, supplements, medical conditions, and lifestyle. Testing it can thus give you a unique insight into your overall health, and how it is evolving over time.

What’s the typical blood work procedure?

In general, blood tests are simple and fast.

Blood tests have traditionally been prescribed by a doctor, but there are more and more blood test services that allow you to get tested directly.

Depending on the blood test you are getting, you may be asked not to eat or drink anything but water before the test.

There are then two main methods to getting your blood tested:

Mail-in at-home finger prick kits

Many common blood tests can now be done from the comfort of your own home, using a simple, painless finger prick.

Your blood test provider will send you a kit that contains everything you need to perform the test. You will then mail in your sample, and usually get your results within a couple of days.

For some tests, studies have shown that the finger-prick method produces the same results as a venous blood draw. For others, such as blood glucose, a venous blood draw must be performed to confirm positive results obtained with the finger prick.

Here’s an instruction video from a UK-based at-home blood test provider Thriva:

Venous blood draws (phlebotomy)

Blood draws are done from a vein, usually in your arm, using a needle. The draw will be performed at a laboratory or in a doctor’s office and take just a few minutes.

To perform a blood test, a nurse or technician (phlebologist):

  1. Cleans the area on your arm where they’ll draw the blood from.
  2. Ties a rubber band to your upper arm to help make your veins more visible.
  3. Puts a needle attached to a tube gently into a vein to draw blood.
  4. Removes the needle from the skin and takes the rubber band off your arm.
  5. Covers the drawing site with a bandage or clean cotton and medical tape.

Are blood tests safe and painless?

The risks of routine blood tests are extremely low.

The volume of blood needed to conduct a blood test is negligible to your system, and it is perfectly safe to get a blood draw multiple times a year.

With a venous blood test, all you’re likely to feel is a little pinch. You may get a small bruise where the needle went in, but it is completely harmless and will disperse on its own.

With a finger-prick blood test, all you’ll feel is a small prick on your finger, and the area the lancet went in might be a little tender for a few hours after the test.

How is my blood tested?

Your blood sample will be processed by a lab, usually within 1-2 days.

You will then receive your report, usually in the form of a list of biomarkers followed by your results and blood test reference ranges.

LabCorp report normal ranges

What is a biomarker?

The term ‘marker’ or ‘biomarker’ is short for ‘biological marker,’ and it stands for anything measurable that can indicate something about our health.

There are hundreds of biomarkers such as LDL Cholesterol, Glucose, Hemoglobin and Creatinine. Each of these can be used to understand your health status and predict the risk of certain diseases.

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