When Should I Worry About...

Magnesium Deficiency: Symptoms, Causes & How to Test for It

April 24, 2023 - Katie McCallum

You're not alone if you have a few questions about magnesium, ranging from what role it plays in your body to whether you should be taking a supplement to ensure you're getting enough.

Supplementation is confusing enough on its own, in fact. Magnesium supplements are heralded for a number of health and wellness benefits — better sleep, improved mood, increased energy, even a reduced risk of heart disease. Frankly, it all sounds too good to be true.

It probably is. There's no clear proof that magnesium supplements provide any benefit to healthy adults who aren't deficient.

But that doesn't mean magnesium itself isn't important — quite the opposite, actually — or that someone who's low in magnesium shouldn't take the deficiency seriously.

"If a person's magnesium levels remain low for long periods of time, they're considered deficient," says Dr. Shelby Payne, a primary care doctor at Houston Methodist. "Identifying and correcting this is important since a deficiency is usually a sign that something else is going on, which is usually an underlying health issue that needs to be addressed."

What is magnesium good for?

Magnesium is an essential mineral, meaning it's necessary for maintaining good health. Its most important job is as an electrolyte that your body uses to regulate many chemical reactions, namely ones that help your cells turn nutrients into energy.

To that end, magnesium supports a number of processes in your body, including:

  • Muscle and nerve function
  • Energy production
  • Blood sugar control
  • Blood pressure regulation
  • Normal heart rhythm
  • Bone health

How common is magnesium deficiency?

How likely is it to be deficient in magnesium? Not very. Because of this, it's not routinely tested for, meaning the exact prevalence of the deficiency is unclear.

"What we do know is that when we look at magnesium levels of people admitted to the hospital, only around 12% are found to be deficient," adds Dr. Payne.

That percentage is likely only that high because magnesium deficiencies can be associated with sickness.

There's a fairly simple explanation for why the deficiency generally isn't very common.

Magnesium is fairly abundant in the foods we eat, naturally found in many of the vegetables, whole grains, nuts and seeds, beans and legumes, dairy products and lean protein sources that make up a healthy diet. Many packaged foods, like breakfast cereals, are also fortified with this mineral.

And even if your intake is low from time to time, your body stores plenty of magnesium in your bones. And healthy kidneys are very good at making sure your body retains the mineral if levels get low. They also get rid of excess magnesium you don't need, by the way, so you don't have to worry about getting too much of it from the foods you eat.

This also explains why most people don't need to take a magnesium supplement. If you nevertheless decide to take one, be sure to let your doctors know so they can help you do so safely.

"There can be side effects — nausea, drowsiness, abdominal cramping, diarrhea — and even risks to taking a magnesium supplement you don't need," warns Dr. Payne. "And you never want to spend money on something that isn't needed or helpful for you."

What are the symptoms of magnesium deficiency?

As mentioned, magnesium deficiency is fairly uncommon. Indeed, it's uncommon enough that even though a simple blood test is all it takes to check a person's levels, it's not typically part of the blood work done at your annual appointment with your primary-care doctor.

"Unless someone is having symptoms of low magnesium or has certain risk factors, magnesium levels aren't routinely checked," Dr. Payne explains. "Another reason we may check magnesium levels is if routine blood work indicates the levels of other electrolytes — particularly potassium or calcium — are off, since this often happens in connection with magnesium deficiency."

That said, it's important for people to know the signs of low magnesium and consult their doctor if they're worried about a deficiency.

Magnesium deficiency symptoms include:

"These day-to-day symptoms can be very vague, so that's where blood work is needed to determine whether magnesium levels are actually low," adds Dr. Payne.

Magnesium deficiency can also cause more severe symptoms — persistent muscle contractions, arrhythmia and seizures — though these are usually only seen in people who are already sick and hospitalized.

What causes low magnesium?

Your first thought might be that low magnesium is the result of not getting enough through your diet, but that's rarely the case.

Instead, magnesium deficiency is typically caused by health issues or medications that affect how well the body absorbs or retains the mineral.

The causes of magnesium deficiency include:

  • Chronic diarrhea
  • Frequent vomiting
  • Malabsorption, due to a digestive condition, such as inflammatory bowel disease (IBD), or a procedure that removes part of the small intestine, namely weight loss surgery
  • Certain medications, including metformin (used to manage type 2 diabetes), proton pump inhibitors (used to treat acid reflux), digoxin (a heart failure medication), chemotherapy and some antibiotics
  • Kidney disease
  • Uncontrolled diabetes
  • Alcohol-use disorder and its related liver problems

"Since having one of these health issues or taking one of these medications increases your risk of deficiency, your doctor will likely check your magnesium levels more routinely," says Dr. Payne.

How is magnesium deficiency treated?

If you're deficient in magnesium, oral supplementation — prescription or over the counter — likely will be recommended.

"There isn't much difference between the formulations of magnesium supplements beyond cost and potential side effects, like upset stomach and GI issues," says Dr. Payne. "If you're deficient, your doctor will help you understand which formulation is right for you."

And there's an even more important step to take when it comes to correcting this deficiency.

"Magnesium deficiency isn't considered a disease itself," Dr. Payne adds. "Rather, it's a sign or side effect of one of the underlying health issues mentioned above. This means the most important step is to search for the cause of low magnesium since this is the key to correcting the deficiency and preventing complications of it."

Untreated magnesium deficiency can, over time, increase the risk of:

"Once we find the primary reason for a person's low magnesium levels, whether it's IBD, a medication the person is taking or something else, treating or managing the underlying issue often resolves the deficiency," adds Dr. Payne.

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