What is "normal”? Understanding your ranges and lab results

Blood tests are useful tools for understanding what's going on inside your body. But they can be tricky to interpret.

Many of us just take a blood test every other year, when symptoms arise or when a doctor tells us. But this is not the optimal path to developing a clear idea about our state of health. Blood tests are a critical part of prevention, with regular checkups to being the healthiest version of yourself. 

They also help detect problems and determine how to go about treating them. In fact, the majority of chronic diseases can be prevented through early detection and lifestyle choices. 

But of course, blood tests can be a stressful thing, especially if your results don’t look quite as expected. So, what does it mean if your results are not quite normal or borderline? We strongly believe that we all should be empowered to make sense of our lab results and health-related information to take charge of wellbeing and fitness. So let’s dive in.

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Reference ranges and what they mean

When you get your blood test results back, you might see that they fall into one of two categories: normal range (which is what you want) or out of range.

The term “reference range” is often used interchangeably with “normal range”. A reference range is used by clinicians to interpret laboratory test results. They are generally determined using data collected from large groups of healthy people who have undergone tests in a laboratory setting. These ranges may be based on a single population of healthy people, or it may be an average of multiple populations. Most lab tests have ranges that 95 percent of healthy people fall into. Normal ranges are different for each lab test, and they can change over time as technology improves, and more people are tested. Doctors use these ranges or reference intervals as guidelines to make more informed decisions.

1 in 20 people have levels outside the “normal range”

Just because you have an out of range test result, it does not necessarily mean you have a health problem. Based on the 95 percent distribution, it also means that 5 percent or differently put 1 in 20 healthy individuals will have levels that fall outside the normal range. That’s also why the term reference range is preferred over “normal range”. While the reference population can be clearly defined, there is no clear definition of what is “normal” in a clinical sense.

Many statistical tests such as lab tests assume a normal distribution. It's a concept that explains how most people are distributed or clustered across a bell curve, with a small percentage of 5 being outliers who are very high or low compared to the average. It's also known as the Gaussian distribution, which is often used in statistics to describe how a majority of things are distributed in the world.

Furthermore, it’s important to know that many labs, test blood samples in different ways. If you receive varying results, it might be because results are reported using different ranges depending on the equipment and methods used, as well as conversion units. 

In fact, there are several more major factors that affect blood test results. Each one of them has an impact on the blood test and may skew the results. 

  • Age
  • Biological sex
  • Stress
  • Genes
  • Lab technique
  • Medication
  • Recent infections
  • Time of day

As you can see, there are many factors that come into play when it comes to interpreting and analyzing lab results. For example, children and adolescents will have different levels of hormones than older adults. Men tend to have higher calcium levels, while women are more prone to lower potassium levels. They also have higher levels of certain hormones during their menstrual cycle and pregnancy because of fluctuating levels of estrogen. This change in hormone levels can affect certain hormone tests, such as those for thyroid-stimulating hormone (TSH). 

Summary:

  • 1 in 20 healthy people will have out of range test results 
  • The term reference range is preferred over “normal range”

Trends over time and continuous testing

A blood test is a great tool to help you understand your health from the inside out. It can show your body's response to stress and diet, as well as the presence of health issues. But a single or isolated test just provides a current snapshot during a single moment in time. It won't tell us everything we need to know about our bodies. It's the combination of tests over time that gives us a more complete picture of what's going on inside of us. 

“Continuous testing shows us trends and patterns over time that are more accurate than a one-time result”. “For example, if a woman’s thyroid-stimulating hormone TSH is elevated above 5.0 mU/L it may indicate an underactive thyroid. But it also may just be a one-time occurrence due to stress, pregnancy, or other hormonal changes. Only after checking the thyroid markers in 3 months, taking factors such as family history, physical discomfort, or symptoms into account, a proper diagnosis can be made”, Dr. Klaus Schmidt-Thome, general practitioner and aware health advisor, explains. 

While in-range results for a blood test will indicate that your body is functioning normally, it doesn't necessarily mean that everything is perfect. When we look at normal results, we need to consider what's normal for the individual—not just the average person in general. Your doctor and regular tests can help you determine what's normal for you and how you might be able to improve upon that.

Summary:

  • The real power of regular blood tests is their ability to provide long-term health trends
  • Normal ranges are a helpful tool, but sometimes these ranges need to be adjusted by a doctor based on your personal health needs

How to best use blood tests

  • Get a comprehensive blood panel 6–12 months each year to stay on top of your health
  • To track progress from changes to your nutrition, workout routine, stress management, or supplements, use smaller tests every 3–6 months (depending on your health goals)
  • Gather all your blood tests in one place (e.g. the Aware app) to detect trends and patterns over time, share them with your healthcare professional and watch out for noticeable changes

The bottom line

Don’t jump to conclusions when your results are a bit off. Talk to your doctor and let them put your labs into context, based on your health, family history, and other factors. Keep in mind that some medications, recent infections, and stress can affect blood test results. Don’t worry about small variations from time to time, they can happen. Your doctor will tell you when and if to retest.

So next time you get a lab report back and the numbers aren't quite what you were expecting, take a deep breath, relax, and talk with your healthcare provider about how best to proceed. Make sure you have all your lab work in front of you, so you can review everything together and ask questions about anything that seems confusing or unusual.

With Aware, you can easily book comprehensive blood tests and do regular checkups. The app makes it easy to gather all your previous and existing blood tests in one place, share them with your doctor, and learn what each biomarker exactly means for your health. Sign up for the Aware early access program and improve your health with us, or read our use our checklist to prepare for your next blood test.

References:

  1. Distribution. Finding and Using Health Statistics. National library of medicine. Sep 9, 2022. 
  2. How to understand your health results. MedlinePlus. September 15, 2022. 
  3. Blood tests. MedicalNewsToday June 27, 2018.