The single most common question I've been getting recently is
This is a very important question because there is more than one way to test your magnesium levels, and it turns out that the most common testing method may not catch all cases of deficiency.
Since magnesium is so important you would think that getting your magnesium levels tested would be quick, easy, and accurate, but just like everything else there are pros and cons to each method.
However, of all the possible testing methods, there is one magnesium blood test that is both easily accessible and accurate enough to be helpful.
How To Test For Magnesium Deficiency
Since magnesium is found inside our bones, muscles, and brain tissue, it can be difficult to properly determine the amount of magnesium in our bodies. As a result, multiple tests have been developed to estimate our total magnesium levels.
There are currently five types of magnesium tests available:
- Exa Test
- Loading/Tolerance Test
All are blood tests except for EXA Test (which uses mouth tissue) and the Tolerance Test (more below).
Serum Magnesium Test
The serum magnesium test is the most common test for magnesium deficiency. As the name implies, it checks the magnesium levels in your blood serum.
The test is commonly done in doctor's offices or labs. Since this is the most common method, it is the most likely test that a doctor will recommend if she suspects a patient is suffering from magnesium deficiency.
What is serum? It is the plasma, antibodies, and non-clotting proteins that are found in your blood. It basically accounts for everything in your blood except anything that is:
- a blood cell
- involved in clotting
The problem with the serum test is that most of the magnesium in our bodies exists in our cells: serum contains less than 1% of our total magnesium.
So it is quite possible for the magnesium levels elsewhere in your body to be low but have the serum test come back normal.
RBC Magnesium Test
Similar to the serum magnesium test, the RBC magnesium test is a blood test.
However, unlike the serum magnesium test, the RBC magnesium test checks the magnesium levels inside your actual cells. In particular it provides a look at the amount of magnesium in the red blood cells (hence RBC).
In general, the RBC test is considered more accurate than the serum test. Why? Because when you are low in magnesium your body takes it from cells for use elsewhere. So if these red blood cells are lacking magnesium then you have an early indicator of deficiency.
This makes it a more accurate test, but since it is more complex than the serum test it tends to be less common.
Ionized Magnesium Test
The least common blood test is the ionized magnesium test. It was developed by two professors, Bella and Burton Altura, at SUNY in New York where they do their testing using a special machine that isolates the magnesium ions.
The ionized test is the most accurate of the blood tests because it tests the actual magnesium ions in your body. Being able to isolate and test the active magnesium ions allows doctors to get a more specific reading of our overall magnesium levels.
Although it is more accurate than the serum and RBC tests, it is difficult for the average person to get tested this way simply because it is only available in a few select locations.
The EXA Test is a method of determining magnesium levels without taking a blood sample.
Instead of a blood draw it is more like a cheek swab: tissue is scraped from the mouth and then tested for magnesium content.
Since most of your magnesium is found in soft tissue, analyzing tissue from the mouth should provide a much better idea of the magnesium content of your body.
However, similar to the ionized magnesium test, the EXA Test requires specific testing materials. As a result it may be difficult to find a doctor or lab that can perform the test and analyze the results.
Finally, there is the Loading or Tolerance test, which requires no blood or tissue at all.
Instead, your doctor gives you a shot of a certain amount of magnesium and then later uses your urine to determine how much your body kept vs. how much it chose to eliminate.
If your body keeps most of the magnesium then it is assumed you needed it and were deficient, and if most of it is eliminated in the urine then the magnesium was not needed and you are not deficient.
Because it takes time for your body to process the magnesium this would involve two trips to the doctor's office or lab, which may help explain why blood tests are more common.
This test is also interesting because it implies that magnesium may be relatively safe to take even if you are not deficient, since the doctor is simply giving you magnesium and seeing what happens.
How Do You Know If You Have Magnesium Deficiency?
The easiest way to get tested for magnesium deficiency is to go to your doctor and explain your symptoms. To be
Since many of the tests above are relatively rare, you will most likely be given either the serum magnesium test or the RBC magnesium test.
With that in mind my suggestion is to see if you can get the RBC magnesium test since it is more accurate while still being something most doctors can request for you.
That said, I've had people tell me their GP only orders the serum magnesium test and they have been unable to get an RBC magnesium test done.
If that's the case for you then you can also order the Serum and RBC tests online through Life Extension.
Life Extension offers all sorts of blood tests, with no insurance required (affiliate link):
Your blood is drawn locally by a medical professional at one of the many official blood labs they partner with. Once it is analyzed, they will send you the results of the tests you ask for.
You place the order online or by phone, go for the blood draw at your convenience, and then you can either get your results online or via mail (or both).
As usual, the blood tests have very few risks associated with them. The main concerns would be excessive bleeding or infection at the site where the blood is drawn, though these risks can usually be avoided by following proper sterilization and blood draw procedures.
And, as always, it is important to make sure whoever is administering the test is aware of any medications you are on so this may be taken into account when analyzing the results of your test.
What Test Did I Have?
Now that you've read all about how to test for magnesium deficiency, you may be wondering which test I ended up choosing.
And the answer is ... none.
When I went to see a neurologist for my symptoms he told me to try magnesium without even testing me. He was absolutely right in his diagnosis, and the fact he didn't have me tested makes me think that magnesium may be one of the safer vitamins/minerals.
I did however learn over time that not all magnesium supplements are created the same.
- Click here to see what I've found to be the best magnesium supplement
Have you been tested? If so please share your story in the comments below.