Magnesium 101

How to Test for Magnesium Deficiency at Home

Magnesium is one of the most important minerals for human health, but it’s also one that many people don’t get nearly enough of! How do you know if you’re one of them? As we’ll explain in this article, it’s not easy to test for magnesium deficiency at home. In this article, we’ll explain what to do instead and how to boost your magnesium levels. 

What is magnesium deficiency?

It’s estimated that up to 50% of the population is not getting enough magnesium in their diets – this doesn’t necessarily imply that all of these individuals are magnesium deficient. The actual prevalence of magnesium deficiency varies depending on the criteria used to define it.

Magnesium deficiency, or hypomagnesemia, means that you don’t have enough magnesium to meet your body’s requirements. This may be due to one or more of the following: 

  • Low magnesium intake from your diet
  • Poor absorption of magnesium in the gut
  • Excessive magnesium loss in the urine

A magnesium deficiency can be described in two ways. The normal range you’d expect to see in a blood test would be somewhere between 0.7-1.0 mmol/L. A frank magnesium deficiency means that your magnesium levels are below 0.7 mmol/L, the “clinical threshold”. However, it’s much more common to have a subclinical deficiency. This is when magnesium levels sit towards the lower end of the range, but don’t quite meet that clinical threshold. 

The danger here is that subclinical deficiency is usually completely silent. Obvious symptoms will only begin to show around the clinical threshold, but the ill effects of low magnesium begin long before that point. In fact, it’s quite common to live with subclinical magnesium deficiency for years and never even reach frank deficiency — all the while enduring some serious health consequences.

How is magnesium deficiency diagnosed?

Magnesium deficiency is tested by using a simple blood test, which you might also hear referred to as a serum magnesium test. The test involves using a needle to take a blood sample from a vein in your arm and then analyzing it in a lab to find out how much magnesium it contains. 

The normal range you’d expect to see in a magnesium blood test would be somewhere between 0.7-1.0 mmol/L. Anything below 0.7 would be considered hypomagnesemia, or magnesium deficiency, while anything above 1.0 would be considered hypermagnesemia, or too much magnesium (although this is very rare). 

Should I ask my doctor for a magnesium deficiency test? 

In the UK, you would typically need to be referred for a magnesium test by your doctor (assuming you don’t want to pay for private laboratory tests). There are three reasons why this isn’t a realistic or reliable option for most people…

1. They only test if there’s a clear reason 

Magnesium tests are not part of a routine blood test, or even a routine electrolyte panel (a set of blood tests specifically for electrolyte levels). Your GP would need a compelling reason to refer you, such as: 

  • Magnesium deficiency is known to be associated with a condition you have, like diabetes or ulcerative colitis. 
  • Magnesium deficiency is a known side effect of a medication you take, like certain anti-diuretics. 
  • You’re experiencing symptoms of serious magnesium deficiency, e.g. heart palpitations. 

Unfortunately, the side effects of magnesium deficiency are often mistaken for other conditions. Migraines, for example, are treated as a condition in their own right, rather than a possible symptom of magnesium deficiency. So while it doesn’t hurt to ask, you may have a hard time convincing your doctor to test you. But let’s say you do…

2. The clinically normal range is flawed 

Your doctor has agreed to refer you for a magnesium test and your levels are 0.75 mmol/L — a good few points above the lower 0.7 limit. Congratulations, you don’t have a magnesium deficiency! Or do you? 

Anything below the 0.7 thresholds is considered a frank deficiency. When levels are low, but not low enough to reach the threshold for an official diagnosis, it’s known as a subclinical deficiency. This is believed to begin at around 0.8 mmol/L. 

Unfortunately, lots of medical professionals don’t devote much attention to subclinical deficiency. Provided that you’re within the clinical range, you may not even be told that your magnesium is low, let alone offered treatment. However, it’s very possible that you’ll still be experiencing some ill effects, and you may not even be aware of them. 

Those dangers of magnesium deficiency we mentioned earlier, like cardiovascular disease, diabetes, and depression? These can — and often do — happen as a result of subclinical deficiency. In fact, one research team claims that subclinical magnesium deficiency is so dangerous to heart health that it should be considered “a public health crisis”. 

3. Serum magnesium may be a poor indicator 

Most of your body’s magnesium content is in the bones, teeth, and cells, with only around 1% floating around in your bloodstream. Or at least, that’s how much should be in your bloodstream; the actual proportion can change for various reasons. 

Take stress, for example. If your body is under stress, this can draw more magnesium out of cells and into the blood. In that case, the magnesium in your bloodstream would represent more than 1% of your total magnesium. 

Therein lies the problem with a serum magnesium test. It assumes that the result represents 1% of your total magnesium, but we actually have no way of knowing if it does at any given moment. If you’re under stress, for example, your magnesium test might show perfectly normal levels in your blood, even while your body’s magnesium stores are depleted. 

Can I test for magnesium deficiency at home?

So if you can’t access medical blood tests, or you can’t rely on the results, what exactly can you do to test for magnesium deficiency?

Lots of people turn to home testing kits to check for deficiencies of nutrients like magnesium. The company mails you a testing kit, you supply a blood sample via a simple finger prick, and then you mail the sample back to them for analysis. 

If you can’t get a test from your doctor, this sounds like the ideal solution right? Well, not exactly. These home test kits have the same limitations as a test recommended by your doctor: they can only test the levels of magnesium in your blood, and they may use the same clinical range to say whether or not you’re deficient. 

If you really want to use a home testing kit and you can afford the cost, then it certainly wouldn’t hurt to try one. However, keep the following points in mind if you do:

  • Look for providers that use named, accredited labs. 
  • Steer clear of providers that make big promises or medical claims about their products, or those that use pushy sales or upsell tactics. 
  • The lower limit for “normal” blood magnesium is 0.7 mmol/L, but subclinical deficiency begins at about 0.8 mmol/L. You should still view a result between 7.0-8.0 as a deficiency. 
  • A “normal” blood magnesium result doesn’t necessarily mean that you have enough magnesium in your body. If your levels are “normal” but you have symptoms and/or risk factors (see below), you may still be deficient. 

The bottom line is that it’s hard to know if you really do have a magnesium deficiency, but if you have more than a few of these symptoms or risk factors, it’s very possible…

Risk factors for magnesium deficiency: 

  • Low intake of magnesium-rich foods.
  • Chronic stress (depletes magnesium levels and hinders absorption).
  • A health condition that causes malabsorption, or poor absorption of magnesium in the gut (e.g. Crohn’s disease, coeliac disease, ulcerative colitis, chronic diarrhea).
  • A health condition that causes excessive urination (e.g. kidney disease, diabetes).
  • Alcoholism or excessive drinking (via kidney disease, excessive vomiting, and digestive disruption).
  • A health condition involving malnutrition (e.g. anorexia nervosa).
  • Certain medications, e.g. certain diuretics, proton pump inhibitors, insulin, antibiotics, antivirals, bronchodilators, bisphosphonates, immunosuppressants, and heart medications. 

Symptoms of magnesium deficiency: 

  • Fatigue/exhaustion
  • Weakness 
  • Muscle cramps, stiffness, or spasms
  • Eye twitches
  • Headaches or migraines
  • Nausea 
  • Numbness or tingling in the arms, legs, hands, or feet
  • Irregular heartbeat 
  • Palpitations (a “fluttering” sensation in your chest)
  • Anxiety, depression, or low mood
  • Stress
  • Insomnia

I have symptoms/risk factors — what next? 

If you think you have a high risk and/or strong likelihood of being magnesium-deficient, you can follow these two simple steps at home. 

  1. Track

First, track your magnesium intake and any symptoms of magnesium deficiency over a period of at least two weeks. Don’t make any changes to your diet or behavior; simply carry on as you are and observe for now!

Keep a diary of what you eat and drink throughout the day and how much magnesium it contains. Some diet tracking apps will automatically calculate the magnesium content in your food for you, but you can also refer to our master list of magnesium-rich foods

You should also track your intake of certain nutrients that can affect magnesium. The most important ones are:

  • Calcium (too much reduces magnesium absorption in the gut)
  • Protein (too much makes you lose magnesium through urination)
  • Selenium (too little is linked to magnesium depletion) 
  • Vitamin B6 (required for cells to take in and use magnesium) 

Also note down any symptoms you have, and how and when you experience them. Insomnia and poor sleep quality are associated with magnesium deficiency, so if you have a smartwatch or wearable fitness band with a sleep-tracking app, use this to monitor how well you sleep. If you don’t have the tech to hand, you can also find lots of free sleep-tracking apps for your phone.

2. Analyse 

After a couple of weeks, you should have a good idea of how much magnesium you’re getting every day. If you’re not hitting your daily required magnesium intake from food (400mg for men and 310mg for women) then you’re almost certainly deficient — even if you’re not noticing any symptoms.  

However, even if you are hitting your daily goals, it’s still possible to be falling short on magnesium. Experts have found that the magnesium content of plants has seriously declined in recent decades thanks to problems like poor soil quality and contamination. Some foods, like refined grains (i.e. white bread, pasta, and rice), undergo a lot of processing too, which strips them of their magnesium content. 

You should also make sure that your levels of those other important nutrients are healthy and balanced so that you can make proper use of the magnesium from your diet. Check that you’re getting the right amount of: 

  • Selenium (75μg a day for men and 60μg for women)
  • Vitamin B6 (1.4mg a day for men and 1.2mg for women)
  • Calcium (700mg a day for men and women)
  • Protein (0.75g per kilo of body weight)

What can I do about magnesium deficiency?

To summarise, you might be deficient in magnesium if: 

  • You don’t get enough in your diet. 
  • You get enough, but you have symptoms and/or risk factors for deficiency. 
  • You get enough, but your other key nutrients are out of balance. 

So what can you do about it? 

The most important thing is to keep on packing your diet with magnesium-rich foods and making sure you get the right amounts of those other key nutrients. However, if you’re still finding it hard to hit your recommended daily intake, or you have a health condition or other factor that affects your ability to properly use magnesium, then a magnesium supplement may help. 

Magnesium supplements are a simple and convenient way to fight magnesium deficiency. They usually come as a compound, which means they’re combined with other ingredients that each add their own unique benefits. One example is magnesium taurate, made with an amino acid called taurine that’s known to promote heart health and regulate blood sugar

We’ve broken down the benefits of magnesium supplements here in our evidence-based magnesium benefits article.

Are magnesium supplements safe?

Magnesium supplements are generally considered safe for most people. Digestive side effects like stomach cramps or nausea are more likely if you stray over the upper limit of 375mg a day, or if you take certain types of magnesium like magnesium citrate or magnesium oxide. Don’t worry though — there are plenty of other types like magnesium glycinate that are much better tolerated, and they’re better for boosting your overall magnesium levels too. 

If you have a health condition or take medication that could affect your magnesium levels, then it’s possible (even likely) that you could benefit from a magnesium supplement. However, magnesium supplements might not be suitable for people with certain conditions and may affect how some medications work. This is very specific to you and your health circumstances, so speak to the health professional that knows you best to make sure supplements are safe for you.