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Magnesium Deficiency: The Complete Guide to Low Magnesium

Magnesium deficiency

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Magnesium deficiency is far more common than most people think. It may be the most common nutrient deficiency in wealthy countries.

Before we dive into magnesium deficiency, let’s first talk about what magnesium is and why it is important for our body.

Magnesium is one of the most important minerals for our body. It plays a vital role in every cell in our bodies, helps to regulate blood pressure, supports nerve and muscle function, normalizes hormones, and even plays a critical role in our mood. This brief list is by no means complete; magnesium does much more for our health.

Despite the importance of magnesium, statistics show that about half of North American adults don’t get the recommended daily intake of magnesium. Magnesium deficiency is common.

In this post, we’ll cover everything you need to know about magnesium deficiency, including causes, signs that you’re low in magnesium, and how to get more magnesium from your diet.

What is a Magnesium Deficiency?

Magnesium deficiency, also called hypomagnesemia, is a condition characterized by low blood levels of magnesium.

Only about 1% of the magnesium in your body is “extracellular”, circulating in your bloodstream. While it is a small fraction of the total magnesium, that 1% is vital. Serum magnesium is required for hundreds of processes throughout your body. (Linus Pauling)

The remaining 99% of your total body magnesium is “intracellular”, or inside of your cells. That vast majority of magnesium is stored in bones and soft tissues, including muscles.

If you do not have enough magnesium circulating in your bloodstream (that 1%), your body may draw magnesium out of your skeleton, for example, compromising the strength of your bones.

While hypomagnesemia is linked to low magnesium intake (relative to your recommended daily intake), the condition is not entirely determined by your intake. The rate at which you deplete magnesium is also an important factor.

If you are low in magnesium, you may experience fatigue and difficulty sleeping. Muscle twitches or cramps, headaches, migraines, and feelings of stress and anxiety are common complaints when you don’t get enough magnesium.

What Does the Research Say About Magnesium Deficiency?

One of the most comprehensive, approachable sources of information on magnesium for health is a book called The Magnesium Miracle by Dr. Carolyn Dean.

However, new research on magnesium comes out continuously because magnesium holds so much promise for health.

In this post, we’ll primarily discuss the research from a 2018 research review article in the journal, Open Heart, by James J DiNicolantonio and peers: Subclinical magnesium deficiency: a principal driver of cardiovascular disease and a public health crisis.

This review covers findings from 233 published scientific articles on magnesium for human health and the authors conclude that widespread magnesium deficiency should be considered a public health crisis because it is behind “incalculable” costs to our healthcare systems and profoundly impacts quality of life:

“Evidence in the literature suggests that subclinical magnesium deficiency is rampant and one of the leading causes of chronic diseases including cardiovascular disease and early mortality around the globe.”

Read on to learn what research says about magnesium deficiency.

Who is at Risk of Magnesium Deficiency?

According to J DiNicolantonio and peers (authors of the research review mentioned above) much of the population may not be meeting the official Recommended Dietary Allowance or RDA for magnesium.

In Canada and the USA, the recommended daily intake is set low relative to what many experts recommend. So, everyone should at least be meeting (if not exceeding) the recommended intake.

Many Canadians and Americans nevertheless do not meet the recommended intake for magnesium because a typical Western diet may only provide enough magnesium to avoid obvious symptoms of deficiency.

Around half (48%) of the US population consumes less than the recommended daily intake of magnesium. Certain subsections of the population are more likely to be deficient than others.

Across the board, women have particularly low intakes of magnesium from diet. One study found that 10 out of 11 apparently healthy women were magnesium-deficient and magnesium deficiency has been found in 84% of postmenopausal women with osteoporosis.

Young people fare better, overall. However, more than 25% of youth have inadequate intakes of magnesium, even if they consume too many calories.

The review authors state in no uncertain terms: “the vast majority of people in modern societies are at risk for magnesium deficiency.

How is Magnesium Metabolized?

To understand how magnesium deficiency is diagnosed, it’s essential to know how magnesium circulates and is eliminated from the body.

Magnesium from food or supplements travels through the gut and is broken down into magnesium ions. A percent of those magnesium ions are absorbed through the small intestine (primarily) into the bloodstream, where magnesium is carried to cells throughout the body.

The elimination of magnesium is mainly controlled by the kidneys. The kidneys filter substances from the blood and produce urine to excrete those unnecessary or excessive substances. So, when we have more magnesium in the bloodstream than our bodies require, healthy kidneys take care of the excess.

This is why magnesium increases in the urine when there is a magnesium surplus and falls when we have a deficit of magnesium intake. Detecting high levels of magnesium in the urine may (counter to intuition) suggest that an individual is not magnesium deficient.

What Causes Magnesium Deficiency?

The research review by DiNicolantonio et al confirms that many factors can drive up an individual’s demand for magnesium, or deplete magnesium stores. That’s why there is no universal minimum requirement for magnesium.

We become magnesium deficient for many reasons. Chronic disease, use of medications, low magnesium in food crops, and overconsumption of refined and processed foods are the main culprits.

There are three main groups of factors that contribute to magnesium deficiency, and we’ll discuss each here:

  1. Low magnesium diet: simply not getting enough magnesium
  2. Poor magnesium absorption: not absorbing enough magnesium into the bloodstream
  3. Rapid magnesium depletion: losing magnesium stores too quickly

1. Is Your Diet Low in Magnesium?

Before you can understand deficiency, it helps to understand where magnesium originates. Magnesium, like many minerals, is naturally found in the soil, in rocks, and in water.

We should get enough magnesium from our diet, simply by virtue of eating foods that are grown in soils with plenty of magnesium, and by drinking water with naturally high levels of magnesium.

However, most of our city water is now very low in magnesium, so water is not an adequate source for most people.

It’s also far harder to get magnesium from food today because of how crops are cultivated.

Modern, industrial agriculture strips water-soluble minerals from the soil and that magnesium is rarely replaced. Low magnesium in the soil affects every type of food we eat, including meat and dairy, because animals also now feed on low-magnesium crops.

According to DiNicolantonio et al, since 1940 there has been a tremendous decline in the magnesium available from foods, including the following. Beside each item is a figure that shows how much less magnesium these foods provide than in years prior to the mid-twentieth century.

  • Beef (−4 to −8%)
  • Bacon (−18%)
  • Chicken (−4%)
  • Cheddar cheese (−38%)
  • Parmesan cheese (−70%)
  • Whole milk (−21%)
  • Vegetables (−24%)
  • Wheat (−20%)

Magnesium is also lost during food refining. The below shows how much magnesium is lost during processing.

  • White flour (−82%)
  • Polished rice (−83%)
  • Starch (−97%)
  • White sugar (−99%)

Processed foods, fat, refined flour, and sugars are all largely devoid of magnesium, and thus our Western diet predisposes us to magnesium deficiency.

2. Are You Absorbing Enough Magnesium?

We absorb magnesium through the gastrointestinal (GI) system, or “the gut”. If your gut is compromised or simply not efficient at absorbing magnesium, you may be at risk of magnesium deficiency.

GI disorders, in particular, can lead to poor magnesium absorption. These can include chronic diarrhea, Crohn’s disease, malabsorption syndromes, celiac disease, surgical removal of a portion of the small intestine, and intestinal inflammation due to radiation may all lead to magnesium depletion. (Linus Pauling)

With age, we tend to absorb less magnesium through the intestines, even in the absence of the conditions listed above. Often this is because hydrochloric acid (stomach acid) levels decline with age, and that acid helps to break down nutrients, including but not limited to magnesium. This is called hypochlorhydria.

3. What Depletes Magnesium Levels?

Even if your body is efficient at absorbing magnesium into the bloodstream, you may “lose” magnesium too rapidly.

Disease, medications, stress, alcohol, intensive exercise, caffeine use, and more can lead to “magnesium wasting” or more rapid depletion of magnesium. It’s also true that we tend to excrete more magnesium as we age.

Here, we’ll discuss how some of the common factors that deplete magnesium, but we also recommend that you read about foods that deplete magnesium.


Coffee and tea may have health benefits. Unfortunately, caffeine also causes our kidneys to expel more magnesium than necessary.

The tannins in tea may also bind to magnesium and make it unusable.

Caffeine alone (or tannins alone) will not cause magnesium deficiency, especially if you consume it in moderation and replace your magnesium levels daily.


Did you know your body uses magnesium to counter the effects of stress? Your body uses more magnesium under stress, which is why stress depletes magnesium levels.

We all experience periodic stress and it may not be harmful. Chronic stress, however, can ultimately contribute to a magnesium deficiency by overstimulating the sympathetic nervous system.


Alcohol forces your kidney to excrete more magnesium and can also decrease the efficiency of your digestive system, further contributing to magnesium deficiency. When patients present at hospitals with diseases related to alcohol use, they are often given a magnesium drip-feed.


Renal disorders or diseases of the kidney can deplete magnesium. Diabetes mellitus… may result in increased urinary loss of magnesium. Multiple other medications can also result in renal magnesium wasting.

Endocrine and metabolic disorders: Several conditions, such as diabetes mellitus, parathyroid gland disorders, phosphate depletion, primary aldosteronism, and even excessive lactation, can lead to magnesium depletion.” (Linus Pauling)

Strenuous Exercise & Sweat

Magnesium along with other electrolytes is lost through sweat. So, in hot weather, in saunas, or when we’re exercising heavily, we lose magnesium more rapidly.

Strenuous exercise increases the loss of magnesium through urine as well as sweat. So, heavy exercise may increase magnesium requirements by 10-20%.


The benefits of many prescribed drugs may outweigh the risks, but certain classes of medications deplete the stores of magnesium in the body.

These medications include proton pump inhibitors/antacids for acid reflux, statins for cholesterol; and blood pressure medications. Other types of medications that deplete magnesium include those with calcium, some diuretics, birth control, antibiotics, anti-inflammatory medications, and no doubt more.

If you are on prescription medication, be vigilant about your magnesium intake,

Other Risk Factors for Magnesium Deficiency

James J DiNicolantonio identified a number of factors that can increase the risk of magnesium deficiency, in addition to those discussed above.

  • Acetaminophen toxicity
  • Aluminium (environmental, including from antiperspirants, and dietary)
  • Aldosteronism
  • Bariatric surgery (small intestinal bypass surgery)
  • Calcium supplements (or a high calcium to magnesium diet).
  • Cancer
  • Cisplatin
  • Ciclosporin
  • Type 1 and type 2 diabetes (uncontrolled glucose levels)
  • Diet high in fat or sugar
  • Digoxin
  • Excessive ingestion of poorly absorbable magnesium (such as magnesium oxide)
  • Enzymatic dysfunction (impaired magnesium distribution)
  • Estrogen therapy (shifts magnesium to soft and hard tissues lowering serum levels)
  • Excessive or prolonged lactation
  • Excessive menstruation
  • Fasting
  • Foscarnet
  • Gentamicin and tobramycin
  • Hyperparathyroidism and hypoparathyroidism
  • Hyperthyroidism
  • Kidney diseases (glomerulonephritis, pyelonephritis, hydronephrosis, nephrosclerosis and renal tubular acidosis).
  • Heart failure
  • Haemodialysis
  • High phosphorus in the diet (soda, inorganic phosphates contained in many inactive ingredients in processed foods)
  • Hyperinsulinaemia (and insulin therapy)
  • Insulin resistance (intracellular magnesium depletion)
  • Laxatives
  • Low salt intake
  • Low selenium intake
  • Liver disease (acute or chronic liver disease, including cirrhosis).
  • Metabolic acidosis (latent or clinical)
  • Pancreatitis (acute and chronic).
  • Parathyroidectomy
  • Pentamide
  • Peritoneal dialysis
  • Porphyria with inappropriate secretion of antidiuretic hormone
  • Pregnancy
  • Tacrolimus
  • Vitamin B6 (pyridoxine) deficiency
  • Vitamin D excess
  • Vitamin D deficiency

How Can You Tell if You’re Magnesium Deficient?

Unfortunately, magnesium deficiency is often overlooked in part because it is difficult to diagnose. Symptoms are generally non-specific, there are numerous contributing factors and no simple method for testing.

Here, we’ve compiled a list of the less severe to most severe signs of magnesium deficiency from the Open Heart Journal article on the public health crisis of subclinical magnesium deficiency.

Less Severe Signs of Magnesium Deficiency

  • Aggression
  • Ataxia
  • Chvostek sign (twitching of the facial muscles)
  • Confusion
  • Cramps (including in the hands and feet)
  • Disorientation
  • Fasciculations (often a flicker of movement under the skin)
  • Hyperreflexia
  • Irritability
  • Muscular weakness
  • Neuromuscular irritability
  • Pain or hyperalgesia
  • Photosensitivity
  • Spasticity
  • Tetany (involuntary muscle spasms)
  • Tinnitus (ringing in the ears)
  • Tremors
  • Trousseau sign
  • Vertigo
  • Vitamin D resistance

Severe Clinical Signs of Magnesium Deficiency

We’ve covered some of these under Health Risks of Magnesium Deficiency below. The severe clinical signs range from serious but not fatal, to potentially life-threatening.

  • Arrhythmias
  • Calcifications
  • Cataracts
  • Convulsions
  • Coronary artery disease
  • Hearing loss
  • Heart failure
  • Hypertension
  • Migraines/headaches
  • Mitral valve prolapse
  • Osteoporosis
  • Parathyroid hormone resistance and impaired parathyroid hormone release/function
  • Psychotic behaviour
  • Seizures
  • Sudden cardiac death
  • Tachycardia

What Are the Health Risks of Magnesium Deficiency?

There are many signs of magnesium deficiency, ranging from less severe to those associated with morbidity.

  • Even if you have normal serum magnesium levels, you could be deficient and predisposed to osteopenia, osteoporosis, and fractures. If you recall, this is because the body will draw magnesium from the skeleton into the bloodstream if not enough is absorbed through the gut.
  • There’s a correlation between low magnesium consumption and risk factors for ischaemic heart disease, such as hyperlipoproteinemia, arterial hypertension, and body weight.
  • Subclinical magnesium deficiency (again, undiagnosed but still serious) increases the risk of numerous types of cardiovascular disease.
  • Possible cardiac signs of magnesium deficiency also include arrhythmias, calcifications, atherosclerosis, heart failure, increased platelet reactivity and thrombosis, myocardial infarction, stroke, and sudden cardiac death.
  • Hypomagnesemia (confirmed magnesium deficiency) detected at the time of hospital admission of acutely ill medical patients is associated with an increased mortality rate.

In their research recommendations, DiNicolantonio and co-authors conclude:

“In order to prevent chronic diseases, we need to change our mindset away from exclusively treating acute illness and instead focus more on treating the underlying causes of chronic diseases, such as magnesium deficiency.”

How is Magnesium Deficiency Diagnosed?

Blood testing or “serum testing” of magnesium may not be useful in diagnosing a magnesium deficiency.

When we do not obtain and absorb enough magnesium through diet, the body will pull magnesium from the bone, muscles, and internal organs to maintain normal serum magnesium levels when intakes are low. Thus, it’s possible to have normal or even higher magnesium levels in the blood even if you are magnesium deficient.

Magnesium deficiency is extremely hard to diagnose since symptoms are generally non-specific, there are numerous contributing factors, and there is no simple way to diagnose magnesium deficiency. Some tests are more reliable than others, however.

Early damage from magnesium depletion isn’t easy to detect because the tissues damaged by magnesium depletion are those of the cardiovascular, kidney, and the neuromuscular systems

Most people have a subclinical (or “silent”) magnesium deficiency, which means they may never be diagnosed but are still at risk. Subclinical deficiencies predispose us to multiple chronic diseases.

How Can You Test Magnesium Levels?

Generally, you would only choose magnesium testing if your healthcare provider suspects you have a deficiency (based on symptoms), despite efforts to raise your magnesium levels.

99% of our total body magnesium is intracellular, which makes testing for deficiency difficult using standard methods. A review of the literature on magnesium deficiency outlines the most reliable methods of testing magnesium levels in the human body.

More Reliable Methods of Testing Magnesium Levels

  • Retention of magnesium load after intravenous administration is likely the best indicator of magnesium deficiency.  This assumes normal kidney function for intravenous magnesium.
  • Retention of magnesium load after oral after its administration.  Assumes normal kidney function normal gastrointestinal and renal function.
  • Mononuclear cell magnesium
  • Muscle magnesium content (muscle biopsy)

Less Reliable Methods of Testing Magnesium Levels

  • Hair magnesium content
  • Bone magnesium
  • Ratio of ionized magnesium to total magnesium (serum or plasma)
  • Ionized magnesium levels – controversial and not always available in clinical labs and hard to measure reliably
  • Lymphocyte magnesium
  • Urinary or fecal magnesium excretion (low or high levels may indicate deficiency)
  • Urinary fractional magnesium excretion >4% (some authors have suggested >2% in those with normal kidney function)
  • Total erythrocyte magnesium levels (magnesium deficiency has been suggested when erythrocyte magnesium levels are <1.65 mmol/L)
  • Total serum magnesium levels
    • Normal serum magnesium is considered to be 0.7–1 mmol/L
    • Optimal serum magnesium concentration is proposed at >0.80 mmol/L
    • A serum magnesium <0.82 mmol/L (2.0 mg/dL) with a 24-hour urinary magnesium excretion of 40–80 mg/day is highly suggestive of magnesium deficiency
    • Magnesium supplementation is recommended in subjects experiencing symptoms that reflect magnesium deficiency if the serum level is below 0.9 mmol/L
    • When serum levels are less than 0.8 mmol/L, magnesium supplementation is necessary

Even the best tests of magnesium levels are often not enough, at least, not if you are relying on only one type of test. Symptoms are still important:

“It is important to note that choosing only one of the aforementioned methods of measuring magnesium deficiency is not appropriate for diagnosing magnesium deficiency. 

In general, either symptoms of magnesium deficiency must accompany the more reliable methods to diagnose magnesium deficiency (eg, intravenous/oral magnesium load, mononuclear cell or muscle), or two or more of the reliable measurements (eg, intravenous/oral magnesium load, mononuclear cell or muscle) should be used in supporting a diagnosis of magnesium deficiency” – Subclinical magnesium deficiency, Open Heart Journal, 2018

How Can You Treat Magnesium Deficiency?

To treat magnesium deficiency, most people simply need to increase their intake. As we’ve seen, most Canadians don’t get enough magnesium from food. Adding more magnesium foods to your diet is a great place to start.

Realistically, not everyone will get enough magnesium from diet. Many of us simply don’t make up through diet the magnesium that we deplete when we drink coffee, tea, alcohol, consume sugary foods, experience stress, use medications, or simply exercise and sweat hard.

While striving to live a healthier lifestyle and consume a magnesium-rich diet, we can also supplement. Choose a high-quality form of magnesium like magnesium citrate.

Magnesium citrate is well absorbed even if you have low hydrochloric acid (stomach acid) which is common as we get older.

If you suspect you may be magnesium deficient because you have GI issues that make it difficult for you to absorb magnesium, speak to your healthcare provider. You can also consider using transdermal or topical magnesium chloride, which may bypass the gut to enter the bloodstream. Alternatively, your healthcare provider may suggest intravenous magnesium.

How to Take Magnesium Citrate Daily

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