The single most common question I've been getting recently is about how to test for magnesium deficiency.
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.
1) Some of the links below are affiliate links.
2) The content provided here is for informational purposes only and should not be used in place of the advice of a healthcare professional. While my wife and I have been taking magnesium supplements every day for years, I can't say how they might affect you. Always consult a doctor if you have health concerns: don't try to self-diagnose!
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.
Serum Magnesium Test: Blood Test, Common, Least Accurate
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.
RBC Magnesium Test: Blood Test, Less Common, More Accurate
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.
Ionized Magnesium Test: Blood Test, Least Common, Most Accurate
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.
EXA Test: Cheek Scrape, Rare, Most Accurate
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.
Tolerance Test: Shot, Less Common, Moderately Accurate
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 honest though, you may not have a lot of control over which test your doctor chooses.
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
As always, you are strongly encouraged to consult with your physician or other qualified medical professional to help determine your own optimal level of magnesium, and to see whether magnesium supplementation is right for you.
Have you been tested? If so please share your story in the comments below.
Dr McMillan says
I have seen many patients with symptoms that do not add up. It is quite difficult to diagnose non-specific symptoms. Often if you try to force a diagnosis it is likely to be the wrong one. Sometimes I advice patients to tap into the value of time. If symptoms are new then they will many times disappear on their own. If the symptoms persist it will usually become associated with other symptoms helping to make an accurate diagnosis.
Treatment too early will mask the diagnosis and increase the probability of long term health problems.
If you have not had significant medical problems as a child it is likely that as an adult the problem is acquired.
Our biggest challenge in current times is nutritional. Most of our diseases are closely linked to diet. Think about what you are eating and remember that an allergy to gluten can produce very subtle symptoms.
Hope you all get better soon.
Ben Adams says
This is a great post! I suspected that I had a magnesium deficiency for ages but my GP just would not give me a blood test for it. In the end I went for a private blood test and they confirmed that I did. Even if I took magnesium instead of getting the blood test, it is purely for peace of mind on my part. I like knowing what is going on in my body!
Hi, I am suffering with almost the same exact symptoms as you did, and my doctor ordered me a serum test for magnesium. Come to find out, it says my magnesium level is too high. Based on my lifestyle and diet, I find this extremely odd. I have been supplementing with dr.’s best for a few days now and it seems to be helping my symptoms. However my doctor recommended I stop supplementing. I am aware that the serum test is not accurate, however I am not a doctor and don’t want to risk hurting myself by supplementing. Also- I have heard that when your body gets enough magnesium it will flush the rest out (diarrhea). While I have been on the supplement I have had no stomach problems or diarrhea. Does this mean my body is absorbing it because it needs it?
My alternative dr told me aside from diarrhea when over doing mag, if you take too much you can blow out your kidneys. Calm is a magnesium powder works great and taste good to me and I take daily and notice headache goes away if I have one or if my stomach hurts or have anxiety. It works for me. My ER friend said that the first thing they do to you when you go to hospital is the IV which is basically electrolytes which has magnesium and patients start to feel better after a hour. Sometimes that’s all they do to patients who come into ER with anxiety or panic, migraines and it works almost every time except for those who are there for the harder stuff like Xanax etc. It also lowers blood pressure. It’s amazing how critical magnesium is in my opinion. Can’t do without!
David Smith says
Most Americans do not get anywhere near their “RDA” amounts. And, RDA is not a good metric of amounts our body really needs. RDA numbers are really just a “subsistence” level of vitamins and minerals. Many Americans need far more than the RDA amounts because they deficient in many nutrients. Still it is impossible to “blow out” your kidneys if you are taking a 100mg or even 200mg magnesium capsule supplement. Why? 100mgs is only 24% of the RDA and 200mgs is only 48% of the RDA of magnesium. Even if you are eating lots of almonds, spinach and avocados AND taking these supplements, your kidneys are not going to be “blown out.”
David Smith says
First, a “serum” magnesium test is the least accurate of the 5 tests Andrew McVagh discussed in this article. You should at least have the RBC test and, if possible, the EXA test. If my symptoms were improving, I would ignore that “doctor” and run as fast as I could to another doctor for a second and even third opinion. You doctor obviously does not know the correct lab test for magnesium deficiency, which affects many more Americans than doctors want you to believe. Your doctor appears to want to keep you hooked on drugs rather than see you take a natural supplement. Unfortunately, that is the paradigm of the U.S. medical model and leaves patients dependent on Big Pharma and doctors who work as their drug pushers. Remember, WE are in control over our own body, NOT doctors! Our body is our most sacred right and what we put into it is our business! Americans must learn to be more cautious toward doctors and understand that U.S. medicine is a massive business with pharmaceutical drugs and underlying driver of profits. Choose to see it differently at your own peril.
CHRIS CUDLIP says
Very interesting website on a very important subject.
However, you’ve made one serious omission.
In the testing section you failed to mention Hair Tissue Mineral Analysis (HTMA).
This is the best measure of magnesium status because it takes into account
the relationship magnesium has with certain other minerals.
The two best labs are Analytical Research Labs arltma.com
and Trace Elements traceelements.com
How do go about getting this analyisis done?
Do you have to go thru a doctor or can you pay for it yourself?
In July 2014 i started having facial tics (like your eye twitches) that eventually moved to my arm, then all over my body. My doc tested all of my electrolytes including magnesium & all were within normal range. I have been to a neurologist who also couldn’t find a cause. These muscle tics wear me out because I can’t sleep at night. I recently heard a doc on the radio talking about magnesium deficiencies causing muscle tics so I started researching. Unknowingly, I actually have several symptoms of magnesium deficiency (fatigue, migraines, chest pains, Anxiety, asthma, & the muscle tics). Would it be dangerous to try a magnesium supplement if my serum test was “normal” at 2.0? (I know it can be dangerous to have to much magnesium too.)
Andrew McVagh says
Hi Felicia. It’s always better to talk to a doctor about any supplement before taking it. Maybe you can ask for an RBC test instead of a Serum test and see what that shows?
That said, my neurologist did recommend magnesium without even testing me so maybe your doctor will do the same?
Well after trawling through awful sounding forums for months trying to self diagnose I happened upon your website!
I have followed an almost identical route to you!
Stating with a small op on my eyelids in May last year which I was stressed about having and had done under IV local anaesthetic after which I had had a virus which didn’t go away, kept on to the doctors that it may be bacterial and wanted anti-bs. They kept saying it’s just a bad virus and will go away in time. I felt awful, swimming head palpitations racing heart, tinnitus, panic attacks blocked ears,really bad sinus headaches. and no energy what so ever and very dizzy!
Eventually was put on anti-bs, which then started my night time delemma. The dreams were very weird, my body then started the inner vibrations!
These vibrations are the most odd sensation and happen when I’m tired before I go to bed, but are really bad when I wake from REM sleep and cause my heart to race and wake me up completely.
I have seen ENT, paid for an MRI of brain and ears as thought it was Labyrinthitis, that had been caused by the ‘virus’ all was clear, had a scan of sinuses….all fine.
Then I thought about seeing a Neurotologist who deals with the inner ear, but decided against it at the time, as my symptoms had improved slightly. ( and everything so far had been self funded!)
I then went to an allergy clinic in London to see if it was mould spores that was causing all my symptoms, I do have an allergy for mould, but not been fighting a toxicity, ( blood tested )so drew another blank.
I was put on various medications and most docs put all this down to stress and anxiety.
7 months later I’m feeling ok, but the sleep situation is still with me.
I first thought it was due to sugar levels causing these vibrations but all this was tested, and normal.
I do eat a lot of sugary foods, I am also on HRT and trying to reduce my dose to see if this was the culprit, still doing this so won’t be entirely sure yet.
I’ve just ordered the supplement you recommend and hope that this might work for me like it has you…… Want to stop feeling like this and feel normal again!
Flo Ferrier says
Hi I have fibromyalgia, high blood pressure, over weight, BPPV, ibs, bladder spasms, and Ostio-arthritis. Gosh when I read all these I think I’m a disaster waiting to happen. Will Magnesium citrate help these systems that I have? I take omega 3 premium. As well as pain relief. I used to suffer badly with Dizzieness but this has deminished some since taking magnesium citrate and the omega3premium. Is there anything you can tell me or am I waisting your time. Thank you.
Hi Flo. Magnesium can help many different things but at this point I think it might be worth asking your doctor to check a bunch of vitamin and mineral levels for you so you can start to home in on the cause of your symptoms. It could be magnesium but it could be a bunch of other things so it’s probably a good idea to start with a baseline.
And if you do get your magnesium tested remember to ask for an RBC magnesium test instead of the regular serum test.
Please stop back and let us know how you make out. I hope you feel better soon!
Hi I having all these symptoms after taking vit D what should I do my seruim magnesium levels are normal but there is no other test available in my country please tell me the right path
Had vertigo symptoms for 3 months but now they think not vertigo at all.Started one morning with spinning and upset tummy which went on for 24 hrs but since then no spinning but feel weird just dizzy,giddy strange head nausea so tried various drugs.On cyclizine that help but want a diagnosis so seeing my neurologist next week.My dr has arranged blood tests,ECG and blood pressure monitor also 7 day ECG but sure the heart is racing just because I’m so scared I’m dying.I do take various other meds as have allergies and severe sinus trouble.But I do have stomach trouble so take lansoprazole which I hear stop magnesium input but I’ve tried to stop them before but need them so can I still take them and magnesium and feel better.Ive just ordered Dr best magnesium as so desperate to stop this awful feeling.
It can be rough being on stomach meds like lansoprazole and omeprazole – by reducing acid production they also seem to reduce our ability to absorb magnesium. I think I saw a version of Prilosec that actually has magnesium in it to prevent that from happening.
Vertigo is awful feeling – I hope you feel better soon!