Heavy metals are difficult to test for and currently, there are no gold standard testing methods. If you go to a conventional medical doctor, they will probably run blood tests (or maybe even roll their eyes at you).
Whilst there's nothing wrong with blood tests, you really need to know what it is you are looking for in order to know the best test to adopt.
With the exception of lead, blood tests are not great ways to test for chronic heavy metal burden in your body because heavy metals, like many other toxins, are lipophilic (they are fat-soluble) which means that they have an affinity for our tissues rather than stay in the bloodstream for long.
Mercury, for example, gets bound up to the sulphydryl groups on amino acids which are present in many tissues, and it also likes to hang out in the brain & thyroid.
If you run a blood test for mercury, it’ll tell you how much mercury you have come into contact with/ingested in the last month or so (e.g. if you ate tuna the night before, it’ll probably be high – but it will not accurately reflect how much mercury you have been exposed to during your lifetime, and how much is bound up in your tissues, aka the body burden.
Aside from the acute toxicity which is measurable from blood tests, the body burden is important and relevant because it is through the binding to enzymes and proteins in our tissues, and interfering with neurotransmitters and hormones that heavy metals exert their toxic effects, for example, affecting ATP production in the mitochondria, leading to fatigue, brain fog etc)
I’m going to focus mainly on mercury here.
There are different types of mercury and in order to know what test is best to run, you need to know what type of mercury you are looking for:
Methylmercury – this is the mercury that is in seafood and fish. It is readily absorbed via a transporter in our gut into our blood and then excreted into the bile via MRP1 & 2, sent to the gut to be pooped out. Depending on how well you empty your bowels and the health of your gut microbiome, up to 80% of the mercury can be reabsorbed from the large intestine back into the blood. So, it is best reflected by a blood test or a hair tissue mineral analysis. However, note that some people may lack the ability to excrete methylmercury into their hair, therefore leading to a falsely negative test. Experienced practitioners may be able to look at how the hair level compares to the blood level to draw that conclusion, also the other mineral composition of the hair may give a clue. This is why it's always a good idea to work with a practitioner knowledgeable about heavy metals as testing is not always accurate. If you do a blood test but are concerned about exposures from 6 months ago, it might not be useful.The average half life of methylmercury is about 1-3 days followed by a slower declined over 1-3 weeks. The reason there is such a wide variation in the half life is because there is a huge variation in our ability to eliminate mercury. Genetic SNPs e.g. in GST transferase, MT1M AA and MT1A CC can alter our ability to eliminate mercury.
Elemental mercury – this is the mercury found in dental amalgams. It is absorbed through a different pathway - via the lungs. Studies have shown that mercury can vaporize and this is then inhaled into the lungs and absorbed. Once it's in the body, it becomes inorganic mercury and is excreted via the kidneys but again – the accuracy of urine mercury depends on kidney function and also how much bound up mercury actually shows up in your kidneys. (some practitioners use a provocation test whereby they use a chelator e.g. DMSA to bind to heavy metals which are then escorted out through the kidneys – this again, depends on proper kidney function for an accurate test). For people with super high levels of toxicity or if the elimination pathways are not open, DMSA can also cause severe side effects. So always work with a doctor who can monitor you.
Inorganic mercury - this is mercury from coal burning, industrial processes and have been found in some cosmetics.
There are also other tests e.g. stool, and most practitioners will use a combination of the different tests available with clinical correlation to come to a conclusion.
This article provides information for educational purposes only and does not constitute medical advice or recommendations. I strongly advise you to work with a practitioner rather than ordering tests off the internet because, as you can see, diagnosing heavy metal toxicity properly requires experience and evaluation of many facets that a single test may not be able to provide.