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The Limitations of Blood Tests

The methods healthcare practitioners of all sorts out there use to “diagnose” your particular health issue are legion.  Many people want an “evidence-based” or “scientific” approach, which to most means there are studies behind it and it is accepted mainstream. For these folks, blood is typically the preferred method, because (in addition to the standard urinalysis) that’s what their doctor does as a first-line look into the body’s chemistry.  Since this is what everyone does, it’s perceived as the main option and everyone keeps doing it.  Momentum is a hell of a thing.

However, over the long-term, have you been happy with how your practitioner has used the info from blood testing?  For example, let’s say your hormones are not in range.  Okay, problem found. Great.  Now what do you do?  Take hormones for the rest of your life to correct the symptom(s) of low hormones?  What if you want to treat the cause?  How does this help you do that, if at all?

I believe there is a better way than blood to assess the body’s longer-term internal workings that just so happens to fall outside of the norm.  In this article, I want to discuss why I have mostly abandoned blood tests ***for nutritional assessment and treatment of longstanding (chronic) conditions.***  After that, I’ll discuss what I have moved to.

How did blood become our first line test for practically everything?  I don’t know, and I don’t have the time or interest in researching it.  My guess is that conventional medicine mainly started using blood tests in hospitals for the treatment of acute conditions.  People with an acute condition in a hospital need a right-here-right-now “snapshot” view of their body’s chemistry so that their doctors can make rapid decisions on their treatment!  If there is one place where blood tests are used best, it is in the acute setting.  This probably then trickled down to the public and general practitioners in the form of: “Well, if it’s good enough to prevent someone from dying in a hospital, I guess we can probably use it on non-acutely sick people too.”

The problem is, testing the blood for that “snapshot” is very dependent on many things, including but not limited to the day of the month, the dawn phenomenon, time of day, (intermittent) fasting, and hydration.  Then, the body does its best to maintain the main electrolyte mineral (calcium, magnesium, sodium, potassium) levels in the blood, or else the heart rhythm is very quickly affected in negative ways.  So…we’re left looking at a set of numbers we get from a “tissue” that is on one hand very labile and changing all the time, while on the other hand it is giving its best poker face. Does it make sense to use this for long-term *nutritional* monitoring of any sort?  Do you think that movie posters tell you all about what’s in a movie? No, I’d say not.

Then…how are the reference ranges—known incorrectly by many laypeople and doctors as “normal” ranges—for blood tests derived?  Here’s a great synopsis:

 The standard definition of a reference range for a particular measurement is defined as the prediction interval between which 95% of values of a reference group fall into, in such a way that 2.5% of the time a sample value will be less than the lower limit of this interval, and 2.5% of the time it will be larger than the upper limit of this interval, whatever the distribution of these values.


Regarding the target population, if not otherwise specified, a standard reference range generally denotes the one in healthy individuals, or without any known condition that directly affects the ranges being established. These are likewise established using reference groups from the healthy population, and are sometimes termed normal ranges or normal values (and sometimes “usual” ranges/values). However, using the term normal may not be appropriate as not everyone outside the interval is abnormal, and people who have a particular condition may still fall within this interval.

However, reference ranges may also be established by taking samples from the whole population, with or without diseases and conditions.

If you didn’t understand the above, it means that the statisticians (not doctors) will be basically “curving” the test so that only 2.5% of the highest and lowest values fall outside the reference range.  As to the assertion of using “healthy” individuals to make up these ranges, just how many truly healthy people do you know, or should we guess at their definition of health and the “fudge factors” they might use?  On the other hand, how many really sick people do you know who go to the doctor and have all their blood work come back within all the reference ranges?  Or, the most likely solution is that the lab mashes up all the people who come in (see last bold sentence in quote above) and curves those numbers to fit.  On that note, it should be obvious that the people getting labs done most often are generally not healthy, and this obviously skews the ranges even further from where they should be.  My suggestion to you is, if you have blood work values that are falling outside of the reference ranges, you should look into it more deeply if your doctor won’t.

Next, someone will bring up that they see (or that they are) a practitioner who does “functional” blood testing.  Been there, done that.  It means that someone decided that the blood ranges are too broad to be useful, and that narrower (“optimal”) ranges should be used.  When I used to think functional blood testing was the best option I had to work with, here’s how it went:

  • Took a seminar on Functional Blood Chemistry authored by this guy.
  • Treated patients exactly as the seminar and manual said.
  • Noticed that the number of supplements people had to take was excessive (and when you hear an ND who is also an ex-supplement store employee say “damn, that’s a lot of pills!” you should definitely take note).
  • The supplements seemed to be really expensive for what they were.
  • There was never any notion of actually fixing the underlying problem through this program, only a lifetime of supplements.
  • Patients eventually quit because they weren’t feeling that much better and they didn’t want to take the pills and/or spend the money.

I eventually quit using this method because A) I didn’t feel we were “treating the cause,” we were simply treating the symptom of blood test values that were not in their “optimal range,” and B) In my experience with it, it wasn’t working well to even manage the symptoms it professed to be addressing.  At all.

Testing blood is also invasive.  Having to go back to the lab to get a forgotten/missed/add-on test is a pain (literally and figuratively).  Maybe you’ve also experienced the joy of going to creepy, dirty labs where the technicians sometimes don’t seem bright enough to collate papers, let alone draw blood cleanly and do the paperwork with it.

Testing blood is significantly expensive.  To run some basic bloodwork and hormones will–if you get really good pay-up-front pricing–cost $200 and up.  If you’ve ever seen the prices the lab charges your health insurance for that same bloodwork, I hope you didn’t hurt yourself when you fell over.

In conclusion, I don’t use blood testing any longer ***for nutritional assessment and treatment of longstanding (chronic) conditions.***  I’m absolutely not saying blood testing is useless, so save the rebuttals. In future posts, I’ll cover in great detail the type of testing that I have found to be infinitely more helpful than blood to treat health conditions at their root, hair mineral analysis.