What Happens in Your Body When You Take Too Much Magnesium

Magnesium is an essential mineral that your body needs. It regulates certain biochemical functions in the body, including protein synthesis, blood sugar control, and blood pressure regulation. It is also necessary for energy production and DNA and RNA synthesis, is important for the structural development of bones, and plays a role in the transport of calcium and potassium for muscle, heart, and nerve function. It goes without saying that your body depends on magnesium in many ways.

However, some people may not get enough magnesium in their diet, so doctors may recommend a supplement, especially to treat certain issues, like constipation, sleep problems, and muscle cramps, says Laura Purdy, MD, a board-certified family medicine physician and medical director of Swell Medical.

But as helpful as a supplement can be, can you take too much magnesium? We consulted the latest research and spoke with medical experts about what happens to your body if you take too much magnesium, including warning signs to watch for.

How much magnesium is safe?

The current Recommended Dietary Allowance (RDA) for magnesium for adults is:

• Ages 19 to 30: 400 milligrams (mg) (men) and 310 mg (women)
• 31 years and older: 420 mg (men) and 320 milligrams (women)

Magnesium is naturally present in many foods, such as almonds, spinach, kidney beans, and tofu. If you’re not getting enough, some doctors may recommend taking a supplement. “It’s important to work with your doctor to discuss your current diet and the right dose for your specific body,” says Purdy. “The recommended dose will vary by supplement and brand. It’s important to follow the label and consult with your doctor, taking into account your current diet and needs. It’s also recommended to take the supplement with food whenever possible,” she says.

What is a magnesium overdose?

Magnesium overdose, also called hypermagnesemia, is very unlikely. The tolerable upper limit of magnesium intake is 350 mg, an amount unlikely to cause side effects. Eating too much magnesium through food is not harmful. However, high doses of magnesium through dietary supplements, such as magnesium oxide, citrate, or chloride, can cause problems. “It’s generally pretty rare, but if you take too much magnesium you can experience diarrhea, nausea and possibly cramping,” says Purdy.

If you take a supplement, stick to the 350 mg limit of supplemental magnesium per day unless your healthcare provider specifically suggests a higher dose, says Katy Dubinsky, Pharm.D., pharmacist and founder and CEO of Vitalize.

Symptoms and signs

Common side effects of excessive magnesium consumption include:

• Diarrhea
• Nausea
• Stomach cramps
• Low blood pressure
• Muscular weakness
• Irregular heartbeat
• Vomiting
• Redness of the face
• Urinary retention (inability to empty all the urine from your bladder)
• Depression
• Lethargy and muscle weakness
• Cardiac arrest

Who is at risk of magnesium overdose?

Although hypermagnesemia is rare, it is something to keep in mind, especially if you have a chronic condition. For example, if you have kidney failure or impaired kidney function, you may be more likely to experience symptoms of a magnesium overdose.

Taking very high doses of magnesium, such as the 5,000 mg found in some antacids and laxatives, has been associated with cases of magnesium toxicity. This does not mean that you should avoid them; instead, be sure to follow the label directions when taking these medications.

Unfortunately, magnesium supplements may not mix well with other medications, including:

• Bisphosphonates (used to treat osteoporosis), which can decrease the absorption of magnesium in the body.
• Some antibiotics should be taken at least 2 hours before or 4 to 6 hours after a magnesium supplement.
• Diuretics can increase the loss of magnesium in the urine and cause a deficiency.

When to consult a health professional

If you have started taking a magnesium supplement and are experiencing the symptoms associated with magnesium toxicity above, call your healthcare professional. This is especially important if you have a kidney disorder.

Treatment and prevention of magnesium overdose

To avoid a magnesium overdose, Dubinsky suggests focusing on dietary sources of magnesium. “Consumers should focus on including magnesium-rich foods, such as leafy green vegetables, nuts, seeds, whole grains, legumes, and dairy products, in their diet to treat a deficiency,” she says.

However, if purchasing a supplement is necessary and recommended by a healthcare professional, follow these tips from Dubinsky:

• Buy high-quality dietary supplements that have been tested for purity and effectiveness. Make sure your product has been third-party tested.
• Choose forms of magnesium with high bioavailability, such as magnesium citrate.
• Do not take more than 350 mg, the recommended upper daily limit, unless specifically recommended by a healthcare professional.
• Ask a healthcare professional if other medications or supplements you are taking might interact with a magnesium supplement.

The essential

Magnesium is a nutrient needed for a multitude of bodily functions, including protein synthesis, muscle and nerve control, blood pressure and blood sugar management, and more. If you are deficient in magnesium, your healthcare provider may recommend that you take a supplement. The tolerable upper intake level is 350 milligrams of magnesium per day, and rare cases of overdose symptoms (such as diarrhea, nausea and vomiting, muscle weakness, irregular heartbeat, low blood pressure) have occurred when a person consumes a very high dose of magnesium in one day.