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5 Side Effects of Taking Too Much Magnesium

These are the warning signs you maybe overdoing it with the popular supplement.

With many turning to dietary supplements for their potential health benefits, magnesium has become a mainstay in many daily regimens. While it's a vital mineral for normal bodily functions, some incorporate an extra dosage for potential benefits, including reducing blood pressure, helping with sleep, aiding with diabetes, and reducing the risk of heart disease, according to Healthline. However, just as with anything else we put into our bodies, there's a limit to how much we can ingest before it becomes a problem with noticeable symptoms. Read on for the side effects of taking too much magnesium, according to doctors.

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Diarrhea and Stomach Issues

woman sitting on couch and clutching her stomach
sebra / Shutterstock

If you've noticed some stomach trouble after changing your magnesium dosage, it might be a warning sign that it's too high. According to Leann Poston, MD,  a licensed physician working as a health expert for Invigor Medical, some forms of the mineral are even used in laxative products because of the effects they can have on the gastrointestinal system.

"Magnesium salts pull water into the gut, causing loose and watery stools," she tells Best Life. "Water is retained in the intestines to dilute concentrated magnesium salts. This overstimulates the gut, causing diarrhea."

Other noticeable symptoms can pop up even earlier. "Along with diarrhea, people can experience stomach cramps and nausea when they take high doses of magnesium for constipation," says Patricia Pinto-Garcia, MD, MPH, senior medical editor at GoodRx.

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A senior woman sitting on the couch with a confused look on her face
Armand Burger/iStock

Feeling foggy can happen for many reasons, from not getting enough sleep to coming down with a slight virus. However, overdoing it on magnesium can also cause people to feel lethargic.

"Very high magnesium levels disrupt normal nerve and muscle function," says Poston. "They can interfere with the release and uptake of brain chemicals that serve as messengers in the brain and body, causing extreme fatigue and confusion."

Low Blood Pressure

Man checking blood pressure

Some people seek out magnesium supplements to help manage their blood pressure. And while Poston says these effects are often "not significant and can be inconsistent," there is the chance that bringing too much magnesium into your system could lead to a problem.

"Magnesium may reduce blood pressure by acting as a natural calcium channel blocker," she explains. "When magnesium competes with calcium for its binding sites on smooth muscle, it can cause the smooth muscle lining blood vessels to relax and dilate. This lowers resistance to blood flow and blood pressure."

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Urine Retention

Close up on man's feet standing next to toilet

If you're having trouble relieving yourself in the bathroom, there's a chance it might have to do with your magnesium dosage.

"Magnesium is involved in regulating smooth muscle contraction," Poston says. "When blood magnesium levels are too high, it can interfere with bladder muscle contraction. This makes it hard to empty the bladder, even when it is overly full and uncomfortable."

Magnesium Toxicity

A person lying in a hospital bed

Pinto-Garcia warns that, in some instances, taking very high doses of the mineral leads to a medical emergency known as magnesium toxicity.

"This usually happens when you take more than 5000 mg of magnesium," she said, adding that this happens usually when people take too much magnesium-containing laxatives or antacids.

Along with the symptoms previously mentioned, magnesium toxicity can appear as a combination of intestinal blockage, flushing, and vomiting. But it can also cause even more serious problems.

"Very high magnesium levels can lead to kidney damage, muscle weakness, trouble breathing, and cardiac arrest," she says. "It's rare, but magnesium toxicity can be fatal. If you think you could have taken too much magnesium, call poison control."

Best Life offers the most up-to-date information from top experts, new research, and health agencies, but our content is not meant to be a substitute for professional guidance. When it comes to the medication you're taking or any other health questions you have, always consult your healthcare provider directly.

Zachary Mack
Zach is a freelance writer specializing in beer, wine, food, spirits, and travel. He is based in Manhattan. Read more
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