Why "within range" on a blood test is not necessarily optimal

Anyone who has looked at their blood test results would have noticed the reference range provided for each individual test, telling you (and your healthcare professional) what is deemed a ‘normal’ result for that test. Whether it’s iron or insulin, oestrogen or progesterone, each test comes bearing a reference range, to serve as a guide for interpreting the results.

But how are these reference ranges derived?

Where do they come from?

Many think they’re based on research, such as that a Vitamin D reading of 50-150 nmol/L is best for health. Sadly, this is not the case. Whilst research may inform some of the reference ranges, it’s not the full picture. Rather, the reference ranges on a blood test represent a bracket into which 95% of results fall within that local area. Essentially, they are a measure of average within the local region. For example, in Australia, where the selenium content in our soil is relatively low, the reference range for serum selenium is around 0.75 - 1.35 umol/L. This is significantly lower than selenium-rich areas of the world, where the reference ranges can be as high as 1.0 - 1.6 umol/L. This means a “normal” reading of 0.85 umol/L in Australia would be considered deficient in countries like Brazil or Argentina, where dietary selenium intake is significantly higher.

This is why it is so important to understand that a reference range is a measure of average, not optimal. Sadly however, the average individual is not necessarily healthy. Many of us fail to get outside each day for our daily dose of vitamin D. We might not reach our daily recommended intake of veggies, and we might indulge in fast food or alcohol a little too often. As naturopaths, we want our patients results to fall within an optimal range for health and wellbeing and we work with them closely to achieve this.

To use an example from practice, we frequently treat young women who are tired, low on energy and short of breath, despite having a ‘normal’ iron reading. So often they say “my doctor tested my iron levels, and they were fine”. And yet they are still experiencing the classic symptoms of iron deficiency. For most labs, the reference range for ferritin (the storage form of iron) is 30 - 200 ug/L. Often these girls fall right on the cusp, such as a result of 34 ug/L. They’re within range, but right at the very bottom of it. Some labs even use a range of 15 - 200 ug/L, so a result of 16 is still technically normal, despite being well outside the range used by other path labs. When we treat patients, we treat not only their clinical signs (such as what they’re blood test is telling us), but also their subjective symptoms (e.g. their fatigue and low energy). In my experience, a ferritin is 18 or 24 is not ideal for most individuals, and certainly not conducive to feeling the best you can.

Furthermore, whilst some reference ranges vary depending on your age and gender, many are standard across the board, meaning the same range is used for a five-year-old girl or a fifty-year-old man. These are two entirely different humans though with different nutritional needs, different risk factors for disease and different patterns of growth and development, so what may be ideal for one may not be ideal for the other. This is why blood test results must always be interpreted of the context of the individual patient - their age, gender, family history, medical history, nutritional requirements and more should all play a part in determining whether or not their blood tests are indicative of ‘good health’.

In clinic, we also look at patterns on blood tests, such as changes that are occurring over time. We might notice a slow, albeit persistent decrease in iron levels, or perhaps a slow but steady increase in total cholesterol. It is so important we take note of such changes, determine why they are occurring and put in place strategies to fix or prevent it, before it becomes a problem. One of the key tenets of naturopathy is holistic and preventative healthcare, so preventing an issue before it arises is integral to our job.

As a naturopath, I encourage my patients to take responsibility for their health and ask questions if things don’t add up. The reference ranges given on blood tests are meant to serve only as a guide; they are a measure of average, not optimal. If you’ve been told your blood tests were “all fine” and yet you’re still experiencing symptoms, seek a second opinion! After all, it’s your health and you have to be your own biggest advocate.

Niki x