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The magnificent mineral magnesium. It seems to play some role in all bodily processes—blood pressure regulation, mood stabilization, sleep, even athletic performance. Despite its relative importance, magnesium deficiency is the second most common deficiency in developed countries throughout the world.DiNicolantonio2018

For this reason, supplementation is often recommended. Otherwise, you may need to up your magnesium intake by loading your daily plate with dark chocolate, almonds, avocados, leafy vegetables, unrefined whole grains, and pumpkin seeds—all rich sources of magnesium. Most of these are also great sources of vitamin D, another important micronutrient.

On the other side of the coin, can you have too much of a good thing? There are a few mild and serious side effects that occur occasionally in people using magnesium dietary supplements. Knowing them could help you avoid the not-so-good feelings that come with supplementing with this micronutrient.

Getting Enough Magnesium?

Before diving into the side effects of over-supplementation, let’s talk about the more common problem of low magnesium levels. Somewhere around 50% of Americans consume less than the recommended daily allowance (RDA) for magnesium;DiNicolantonio2018 which for men is about 400mg of magnesium per day and for women is 310mg - 320mg per day. Importantly, this number increases during pregnancy and breast-feeding. Pregnant women should shoot for an intake around 350mg - 360mg of magnesium per day, and breast-feeding women around 390mg.

Not getting enough magnesium could have serious implications for health; several observational and experimental studies show a role of magnesium in the risk for certain immune, cardiovascular, and musculoskeletal diseases. Even if you don’t have dangerously low levels of magnesium, subclinical deficiencies can still have negative health effects. Many of these might not be overly noticeable.

Why is deficiency so common? Inadequate dietary magnesium intake (from food) seems to be the major reason.

Much of our food—whether through industrial manufacturing or mineral-depletion in the soil—has been stripped of magnesium.

Even foods claiming to be high in magnesium might not contain as much magnesium as is claimed on the package or internet sources for nutrition information. How do you know if your magnesium intake is suffering?

Side Effects of Magnesium Deficiency

If you don’t get enough magnesium, your body will let you know. Magnesium has an active role in so many processes related to metabolism, electrical activity, and circadian rhythms that not having enough will throw a wrench in your physiology.

Many of the side effects of magnesium deficiency are considered “subclinical,” meaning that there aren’t really any clinical signs or disease-like symptoms that will have your doctor paging the ICU. No, subclinical deficiencies are often “silent,” but this doesn’t mean they aren’t harmless. Small reductions in biological function occur with even minor deficiencies, keeping you from achieving your peak potential.

Subclinical deficiencies aren’t uncommon. It turns out that about 10% - 30% of any population might be walking around with a low levels of magnesium—and it is estimated that many of us don’t get the RDA from our diet. So, unless you’re already using dietary supplements, there’s a chance you might be running low.

Don’t Spaz Out

As an electrolyte, magnesium helps to maintain fluid balance and electrical activity inside the body. Muscles, the brain, and the heart—each of these critical organs rely on a proper balance and conduction of electrical signals with the help of magnesium. For this reason, common signs of a magnesium deficiency include muscle spasms, twitches, even minor tremors. Other involuntary movements called “fasciculations” are another sign. These little flickers of motion under the skin are small, spontaneous contractions afflicting just a few tiny muscle fibers, a misfiring of motor neurons of sorts.

Muscle cramps are another well-known side effect of magnesium deficiency. Cramps often occur in the hands and feet. Do your fingers and toes “curl up” without warning, then fight to unfurl themselves no matter how hard your try? You’re not frozen, but may be experiencing magnesium-deficiency related muscle cramps.

Feeling Moody?

Magnesium is crucial for the function of several mood-regulating neurotransmitters. Four super-important ones include gamma-aminobutyric-acid (GABA), a neurotransmitter with calming properties, glutamate, an excitatory neurotransmitter, serotonin, the “feel good” hormone, and dopamine, the “reward” hormone. The brain relies on magnesium to keep up the levels of these molecules to allow proper coordination among all of our brain systems.

So what happens without enough magnesium to support the production of these critical brain-signaling molecules? Our mood, thoughts, and feelings can be thrown out of whack as a side effect.

These mood-related effects include things like aggression, anxiety, and irritability, all side effects which have been noted in magnesium-deficient individuals.Boyle2017 Magnesium deficiency might even result in depressive-like symptomsJacka2009 and annoying migraine headaches.

Low magnesium status is also known to impair the capability to learn and remember information.Bardgett2005 Another side effect of magnesium deficiency might be the fact that you can’t remember where you put the remote...again!

Night Owl

You’ve heard of melatonin, the molecule responsible for signaling to our body that it’s time to tuck in for the night. But, magnesium is also well-known for its involvement in helping to regulate sleep cycles and the quality and quantity of sleep. Tossing and turning all night? One side effect of magnesium deficiency is poor quality sleep and insomnia-like symptoms.

Studies have shown that a magnesium deficient diet can throw off patterns of sleep organization, lead to a higher amount of brain excitation during sleep (not something you want when trying to relax), and up to a 24% reduction in slow wave sleep.Depoortere1993 This stage is the deepest stage of sleep, where we consolidate memories, among other important brain processes.

Magnesium deficient individuals also report side effects of disturbed sleep, and this seems to increase with age, where many people show side effects of sleep disorganization—lower REM sleep and abnormalities in brain EEG signals measured during slow wave sleep. Magnesium supplementation has been shown to reverse many of the age-related changes in sleep and sleep quality.Held2002,Nielsen2010

The sleep-related side effects occur because without magnesium to regulate the calming effects of GABA and the sleep-promoting qualities of melatonin, it becomes all the harder to quiet the mind for a deep slumber.

One of the beneficial aspects of magnesium is its ability to produce a calming effect on the central nervous system.

A quiet and relaxed mind is able to fall asleep much easier than one buzzing with anxiety and stress.

Short term side effects of magnesium supplementation.

Long Term Side Effects of Deficiency

Muscle cramps and restless nights—these are some short-term adverse effects of magnesium deficiency that might be simple annoyances in your day to day routine rather than larger signals that your health is in danger. In the short-term, magnesium deficiency can impair mental and athletic performance, but can easily be reversed through a magnesium-fortified diet and dietary supplementation.

But long-term health is something everyone should think about, not just how you feel today. In this case, carrying a deficiency over a longer span of time has the potential to result in direct and indirect chronic health consequences. Magnesium deficiency has many long term side effects worth knowing about so you can work to prevent them in your nutrition or supplementation strategy.

Heart Healthy Magnesium

Magnesium helps to keep our cardiovascular system in check. Without magnesium, the blood vessels aren’t able to properly relax (known as vasodilation) to feed muscles with blood and nutrients and maintain a low but adequate blood pressure. It does this in part by helping the body release nitric oxide (NO), a molecule responsible for blood-vessel relaxation. Not having enough magnesium around can mean less NO, and vessels that are less responsive. The latter, known as endothelial dysfunction, is a well known risk factor for heart disease and kidney disease. Endothelial dysfunction has been observed in people consuming a magnesium-depleted diet.Maier2004

When blood vessels don’t function properly, side effects can include a poor exercise capacity, reduced ability to respond to stress, and a heightened risk for developing atherosclerosis—a narrowing and hardening of the arteries. In this way, chronic magnesium deficiency can lead to a greater risk for developing heart disease and kidney problems.

The evidence supports a link between magnesium deficiency and cardiovascular disease—having higher levels of magnesium is associated with fewer metabolic risk factors like high blood sugar, a reduced risk of stroke, and a lower risk of cardiovascular disease.RosiqueEsteban2018

High intake of magnesium, if it boosts your body’s levels, might protect against an achy breaky heart.

Since magnesium helps regulate blood pressure, another side effect of low magnesium is (not surprisingly) high blood pressure, also known as hypertension. There is an inverse relationship between levels of magnesium and blood pressure, meaning that low levels of magnesium are associated with elevated blood pressure.Jee2002 People with hypertension have been reported to have low concentrations of magnesium flowing throughout their cells.Paolisso1997 Losing out on the vasodilatory effects of magnesium can have negative long-term side effects, causing undue stress on your heart and leading to kidney problems and other organ damage.

Keep The Rhythm

To keep our hearts beating properly, we require adequate levels of magnesium and a proper balance of magnesium, calcium and potassium, the body’s main electrolytes. If levels of magnesium are too low, this may lead to a lower activity of a key ATP producing enzyme in the heart. This results in more sodium and calcium inside heart tissue. Electrical activity becomes unbalanced.

Magnesium deficiency can throw off the heart’s normal synchronicity, perhaps leading to irregular heartbeats, known as arrhythmias. These are mostly non-fatal and likely won’t lead to cardiac arrest. Nevertheless, arrhythmias of any kind aren’t something to mess with.

In a number of studies, a low-magnesium diet of about 130mg/day led to an increase in the number of irregular heartbeats experienced by women.Klevay2002 Another study, again in women, observed that a diet including only 100mg/day of magnesium caused atrial fibrillation (a type of arrhythmia) and also increased blood sugar levels.Nielsen2007 The arrhythmic side effects of magnesium deficiency are well supported by experimental evidence. Keep the beat by getting your magnesium.

Magnesium and Metabolic Health

Through its regulation of several transporters and enzyme activity, magnesium plays a major role in glucose metabolism and insulin action. Insulin is the hormone that allows our muscle cells to take up blood sugar. Our ability to regulate glucose and insulin matter a lot for long term health.

One side effect of long-term deficiency is dysregulated metabolism, which often takes the form of type 2 diabetes. Diabetes is often associated with deficient levels of cellular magnesium, and low magnesium levels are commonly found in people who have poor blood sugar control.Barbagallo2015

The chronic side effects of not getting enough magnesium are insulin resistance and a reduced ability to use glucose in cells. This points to a potential causal role of magnesium deficiency in metabolic diseases like type 2 diabetes.

Luckily, these serious side effects can be reversed.

Studies show that supplementing with magnesium can restore normal magnesium levels in deficient people while also improving insulin sensitivity and overall control of metabolism.RodriguezMoran2003

Without the proper ability to utilize fuel from food sources, overall health can suffer. Even in non-diabetics, magnesium deficiency may potentially lead to a reduced ability to generate energy from food substrates. The side effects of this are clear—you won’t feel as good as you could and athletic performance may even suffer.

Long term side effects of magnesium deficiency.

Avoiding Deficiencies

Step one, try to up the source of magnesium rich foods in your diet. These include nuts and seeds, dark leafy vegetables (ever heard of kale?), dark chocolate, fatty fish, meats, and some fruits like bananas.

If you’re already eating a lot of these foods or are worried that they may not be providing you with all of the magnesium you need, then dietary supplements might be a a good option. Magnesium supplementation is affordable, easy, and carries relatively few risks associated with downing too much for the body to handle.

However, as with all supplements, there are also side effects related to high, rather than low levels of magnesium.

Can You Over-Supplement?

It is highly unlikely that magnesium toxicity or hypermagnesemia (too much magnesium) will occur due to dietary intake alone. Our kidneys are pretty adept at handling excess magnesium; they can boost excretion to up to 100% in the face of increased intake from diet. However, they’re less able to handle a buildup of too much magnesium that might occur due to large doses obtained through magnesium supplements.

When you begin to add supplemental magnesium, you enter a slight risk of “overdoing it.” Any additional (i.e. supplemental) magnesium you plan to take shouldn’t exceed 350mg/day for women or 400mg/day - 420 mg/day for men. At the proper dose, magnesium supplementation is relatively safe for most people when taken orally.

However, if taken in a high dose that causes magnesium to build up in the body, supplementation could possibly lead to some unwanted and serious side effects. Whether you’re ingesting magnesium citrate, magnesium sulfate, magnesium oxide, magnesium aspartate, magnesium glycinate, or magnesium chloride, all forms of magnesium can be both beneficial or potentially irritating.

Side Effects of Supplementation

Again, most forms of magnesium appear to be safe and well tolerated at doses of 200mg/day - 400mg/day. Toxicity may be pretty rare, but some irritating side effects have been noted in people supplementing with high doses of magnesium. It might be good to know what to look out for.

The risk of too much magnesium, leading to magnesium toxicity, is generally low because our kidneys are able to finely regulate how much magnesium we have at any given time.

This is accomplished through magnesium excretion in the urine. If we are running low on magnesium, the kidneys excrete less, conserving magnesium. On the other hand, the kidneys also help prevent magnesium overload by increasing how much we excrete when they sense high levels—such as in the case of supplementation overdose or in the unlikely case that your dietary intake skyrockets.

For this reason, too much magnesium is much more rare than too little. However, it’s still valuable to take stock of how much you’re supplementing to avoid any adverse effects.

Gastrointestinal Side Effects

The most common (and feared) side effect of magnesium supplementation is diarrhea. 12% of subjects in one magnesium supplementation study experienced diarrhea, but this was only in the high dose group.Delordes1998 Typically, only doses over ~600mg are associated with diarrhea-like symptoms.

Magnesium in the form of magnesium hydroxide (milk of magnesia) and magnesium citrate are sometimes taken as over the counter laxatives in people with constipation, so it’s no surprise this is one crappy symptom. When the osmotic magnesium salts are ingested in high quantities, the unabsorbed salts pull water into the colon and intestines. Magnesium also stimulates gastric motility—moving things right along.

Other commonly reported effects include an upset stomach, nausea, vomiting, and abdominal cramping. These all relate to magnesium’s effect on the intestine. Forms of magnesium supplementation reported to more often cause symptoms include magnesium carbonate, magnesium chloride, magnesium gluconate, and magnesium oxide.

Cardiovascular Side Effects

Since magnesium helps keep blood pressure at safe levels, it is sometimes used to treat high blood pressure (hypertension).

For this reason, overdosing on magnesium supplements may lead to a condition known as hypotension—when blood pressure drops too low. And, while high blood pressure is damaging, low blood pressure could impair your ability to regulate blood flow and lead to dizziness or light-headedness. Magnesium sulfate has been used in clinical studies to induce “controlled hypotension” and lower patients blood pressure for surgery.Yosry2008 The doses used here are exponentially large (40mg/kg) and were injected by IV, so they differ a lot from conditions of oral dietary supplements you might be able to purchase.

In some cases of long-term over supplementation, high magnesium levels in the blood might lead to a slowed heart rate (bradycardia) or irregular heart beats. These are rare side effects, however, and are only usually seen in healthcare settings where high doses of magnesium are given as therapy or through IV injection.


One reason many people choose to supplement with magnesium is because some forms of this mineral help to promote sleep. This is why magnesium glycinate is present in several supplements and helps act as a rejuvenating sleep aid designed to help you fall asleep and achieve high-quality restfulness.

But not all time is nap time. One of the side effects of magnesium might be drowsiness. In this case, you should consider magnesium supplementation at the end of the day (with dinner) to prevent the midday magnesium slump.

Potential side-effects of magnsium supplementation.

Adverse Interactions

Taking antibiotics, certain medications, or on hormone replacement therapy? Magnesium interacts with various drugs and nutrients—it may be important to know if magnesium will play nice with whatever else you’re taking in order to avoid an adverse interaction.

Interactions with Medications

Due to the inherent blood-pressure lowering effects of magnesium, negative side effects may occur if you’re on blood pressure medications or calcium channel blockers, also known as CCBs. Dizziness, nausea, and excess fluid retention are all likely if you double up on magnesium while taking these cardiovascular medications.

Certain antibiotics used in healthcare may be rendered less effective if taken with magnesiumincluding quinolone and tetracycline antibiotics. It is suggested that if you are going to continue supplementing with magnesium throughout your antibiotic treatment, be sure to supplement magnesium 1 to 2 hours before taking your meds—as this will help avoid the interference with absorption.

Magnesium could also lead to too much relaxation (is there really such a thing?) Turns out, magnesium increases the muscle-relaxing effects of certain anesthetics and could also enhance the effects of certain muscle relaxants. Tell your doctor or anesthesiologist if you’re taking magnesium before going under the gas.

Avoiding Side Effects

Steering clear of the potential unwanted gastrointestinal or other side effects of magnesium supplementation can usually be avoided by using a proper dose. The tolerable upper limit set by the Food and Nutrition Board (FNB) of the Institute of Medicine (IOM) is 350mg/day of supplemental magnesium. Remember, the sources of magnesium you get from the diet aren’t included in this number.

Taking magnesium supplements along with a meal or any kind of food may reduce the gastrointestinal effects. Don’t take them on an empty stomach.

And finally, just do your research. If you are supplementing or plan to supplement with magnesium to avoid a deficiency or receive other benefits, make sure there aren’t any known adverse interactions with medications or drugs you might be taking. Get medical advice from a healthcare professional if you plan to supplement.

Make sure you’re getting a high-quality magnesium supplement adequately formulated with modest levels of magnesium. Stay informed, and get to your peak potential.

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