Signs and Symptoms of Too Much Magnesium

Magnesium is an essential mineral that helps your body function at its best. But too much magnesium — which can be the case if you take a supplement, for instance — can lead to side effects.

According to the U.S. National Library of Medicine, magnesium is necessary for more than 300 biochemical reactions in the human body. Magnesium benefits include:

• Maintaining nerve health
• Maintaining muscle function
• Promoting bone health
• Regulating heart rate
• Promoting immune function
• Producing energy and proteins

The best way to get the mineral is through natural food sources, according to National Institutes of Health (NIH). Per the NIH and the Cleveland Clinic, magnesium-rich foods include:

• Almonds: 80 mg
• Spinach: 73 mg
• Black beans: 60 mg
• Cashews: 74 mg
• Peanut butter: 49 mg
• Bread (2 slices): 46 mg
• Avocado: 44 mg
• Baked potato: 43 mg
• Brown rice: 42 mg
• Oatmeal: 36 mg
• Peanuts 63 mg
• Dark chocolate: 50 mg
• Salmon: 26 mg
• Halibut: 24 mg
• Chicken breast: 22 mg

You can also take magnesium in supplement form. However, it's always best to try and get your fill of the nutrient through food sources alone and only try an over-the-counter (OTC) product if your doctor recommends it, according to the Mayo Clinic.

If you get too much magnesium from food, your kidneys will excrete the excess in your urine (unless you have an underlying health condition that affects your kidney function), per the NIH. But you can overdose on magnesium by taking high-dose supplements (typically, that means doses of 5,000 mg/day or higher), which can lead to potentially harmful side effects.

To help you determine if you've taken too high a dose, here are the symptoms of too much magnesium.

Magnesium supplements are often used as a laxative to treat constipation that may arise from a variety of conditions, according to the Linus Pauling Institute. However, taking too much magnesium commonly results in diarrhea.

Some forms of the supplement may put you at higher risk for bowel troubles than others, per the NIH. For instance, the following types of magnesium are most often reported to trigger diarrhea:

• Magnesium carbonate
• Magnesium chloride
• Magnesium gluconate
• Magnesium oxide

That's one of the benefits of magnesium glycinate and magnesium citrate; they are less likely to cause diarrhea. And diarrhea isn't the only digestive symptom of a magnesium overdose — magnesium can also upset your stomach (more on that in a moment), per the NIH.

Does magnesium make your stomach upset? If so, you're in good company — nausea is another one of the most common side effects of too much magnesium, according to the NIH.

Magnesium can give you a stomach ache or nausea because high doses of the nutrient can disturb your gastrointestinal function. That's why magnesium stomach upset is often accompanied by diarrhea and stomach pain or cramps, per the NIH.

Because high amounts of magnesium can cause an upset stomach, your best bet is to skip the supplements and stick to plant sources of the mineral instead, according to the Mayo Clinic.

Magnesium and stomach upset isn't the only concern if you're taking a supplement. High doses of the mineral can also cause your energy levels to drop, resulting fatigue or exhaustion, per the Linus Pauling Institute.

Lethargy is typically an earlier sign of too much magnesium in your blood, according to the NIH, but can progress to some of the side effects outlined below.

Your muscles may also begin to physically deteriorate and weaken as magnesium overdose progresses, according to the NIH.

That's because magnesium is directly linked to muscle function and the production of new proteins in the body, per the NIH. But without a healthy balance of the mineral, protein production can fall out of whack. And without these proteins, it's difficult to maintain muscle strength.

Another symptom of a magnesium overdose is difficulty breathing, according to the NIH.

This is typically a sign of more advanced magnesium toxicity, which can occur if you have megadoses of the mineral, per the Linus Pauling Institute.

Cognitive processes may be slower and it may be increasingly difficult to focus your mind when your body is experiencing a magnesium overdose, according to the Linus Pauling Institute.

This is also a later effect of magnesium toxicity, and usually occurs with other symptoms like lethargy and weakness.

Magnesium poisoning can lead to a disturbance in cardiac rhythm, which in turn, can have harmful effects on cardiovascular function, according to the Linus Pauling Institute.

Typically, this may feel like you have an irregular heart beat, per the NIH, and is often accompanied by the symptoms listed above.

Extremely high levels of magnesium in your blood — a condition called severe hypermagnesemia — can also lead to heart attack, per the Linus Pauling Institute. So if you experience an irregular heart beat after taking high doses of the mineral, seek medical care immediately.

You can have too much magnesium in your blood whether or not you have an underlying kidney disorder, though people with kidney disease are more at risk for magnesium overdose, per the Linus Pauling Institute.

That said, those without kidney problems can still experience deteriorating kidney function if they take magnesium in ultra-high doses.

Taking megadoses of magnesium can lead to too much of the mineral in your bloodstream, which may cause a fall in blood pressure known as hypotension, according to the Linus Pauling Institute.

Per the Mayo Clinic, symptoms of hypotension include:

• Dizziness or lightheadedness
• Fainting
• Blurred or fading vision
• Nausea
• Fatigue
• Lack of concentration

Other symptoms of too much magnesium — like lethargy, confusion, irregular heart beat and kidney dysfunction — can also contribute to hypotension, per the Linus Pauling Institute.