top of page

Blood test standards?

Updated: Dec 18, 2023

When the doctor has your blood tested, the results are compared with “Reference Ranges” (normal levels) for each test and then the doctor is advised by bolded results, asterisks, or comments linked to the results that fall outside this range.

For example if your HbA1c is 5.2% (33 mmol/mol) and the normal level is under 5.8%, (Under 40 mmol/mol) then all is good and sometimes the doctor will not even bother to tell you things are OK. No news is considered good news.

But an interesting question arises as to how is the reference range determined. We can’t ask your body, and everyone is a little unique with some people seemingly perfectly healthy with blood test results that would be very unhealthy for others. You probably know someone or heard of someone who was a regular smoker and lived to a ripe old age, while others are sickened by second hand smoke alone.

So in order to set a reference range, results of many people are viewed over time and a level is set based on actual test results for seemingly healthy people. It is usually set at the range that 95% of the tested people fall within. Each laboratory validates and sets their own reference ranges, due to slight differences in the testing, equipment, testing process, and differences in their test population. This must be why it is often noted that the “normal” level will vary by laboratory.

Here is a statement from a laboratory:

Adult reference Range values were established from wellness participants with an age mix similar to our patients.

But what is to happen if, over time, the general results move away from the reference range? Laboratories have little choice but to “adjust” the “reference range” to reflect the real results they are now seeing in their patients. With only 12% of USA adults now recording as metabolically healthy, what is happening to the reference ranges for our general testing?

This should be a warning to us to be aware that “normal” may not be healthy. If your doctor is not astute about this shift in test results over time, the information you get (or don’t receive) to suggest that all is good because your results are within the references ranges may be rubbish.

To compound this problem, in many cases insurance will only authorize and cover the cost of tests where there is reasonable grounds to suspect a problem. The result is that the tests are therefore not representative of a healthy population, but are skewed towards unhealthy because only suspected unhealthy people are actually tested. If your results are in the “normal” window, they may actually be showing that you are sick.

This from the American Center for Disease Control (CDC). In 2009, the average waist size for women in USA was 37.4 inches, in 2019 it was 38.7 inches. Any reference range (normal) for USA women will have increased by about 1.3 inches, but “healthy” has not increased by 1.3 inches.

As an example of this, blood cholesterol reference ranges have been gradually declining, not because lower cholesterol is healthier, (it’s not, read about it in my book.) but because more and more people have been prescribed statins and this is gradually lowering the overall readings for cholesterol. Since we now know that higher cholesterol is correlated with lower overall death rates in people aged over 65, we have the strange situation where the doctor is seeing lower cholesterol as ideal only at lower and lower levels, while the patient would actually be healthier and have a more robust immune system with higher cholesterol levels.

So next time your doctor says that your tests have all come back “normal”, you may need to do your own research.

George Elder, Author, "Take Back Your Health", Amazon here.

11 views0 comments

Recent Posts

See All


bottom of page