Medically reviewed by Elizabeth Barnes, RDN
Taking too many magnesium supplements or magnesium-containing medications can result in a magnesium overdose or toxicity. A magnesium overdose, which results from high levels of magnesium in the blood, is called hypermagnesemia.
Magnesium is a vital mineral that aids in muscle and nerve function and energy production. It also helps to keep bones strong and has a role in regulating blood sugar and blood pressure. Most people can get all the magnesium they need from their diet, while others take magnesium supplements to meet their daily requirements.
Symptoms of too much magnesium in the body are gastrointestinal troubles, muscle weakness, headache, low blood pressure (hypotension), and facial flushing. Untreated hypermagnesemia can lead to severe symptoms, and extremely high levels of magnesium can be fatal for some people.
Magnesium overdose or toxicity is rare in most healthy people but can occur in people taking magnesium supplements or those with impaired kidney function. Some laxative and antacid medications contain high amounts of magnesium and should not be taken in high doses or for long periods.
This article will cover the symptoms of too much magnesium, sources of magnesium, toxic levels, treatment for overdose, and more.
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Symptoms of Too Much Magnesium
The symptoms of hypermagnesemia typically won’t be felt until magnesium levels are incredibly high. When there are signs or symptoms, they may include:
- Facial flushing
- Urinary retention (being unable to empty your bladder completely)
- Stomach and intestinal troubles, such as bloating, cramping, diarrhea, etc.
- Loss of appetite
- Signs of low blood pressure, such as include blurred vision, dizziness, fatigue, and trouble concentrating
- Muscle weakness
More severe signs and symptoms of hypermagnesemia include:
- Slow or irregular heartbeat
- Breathing difficulties
- Signs of shock, such as rapid, weak, or absent pulse, shallow breathing, cool and clammy skin, light-headedness
How Much Magnesium Is Too Much?
People do not get too much magnesium through diet alone because the kidneys excrete excess magnesium into the urine. However, if taking magnesium supplements or medications that contain magnesium, it is possible to take too much and have health consequences.
The tolerable upper intake levels for magnesium from supplements or medications are:
- 1–3 years old: 65 milligrams (mg)
- 4–8 years old: 110 mg
- 9–18 years old: 350 mg
- 19 years old and over: 350 mg
These levels are the same for people of all sexes, including those who are pregnant or lactating (breastfeeding). Exceeding these levels may result in diarrhea, cramping, and nausea. These levels do not include magnesium from dietary sources, only magnesium from supplements or medications.
Taking amounts of 5,000 mg per day can result in magnesium toxicity. This might happen by taking a very large dose of laxatives or antacids that contain magnesium. Toxicity can produce severe symptoms, including low blood pressure, weakness, difficulty breathing, irregular heartbeat, and death.
Sources of Magnesium
Most people can get all the magnesium they need from their diet, while others take magnesium supplements to meet their daily requirements.
Magnesium is widely available in plant and animal food sources. The best dietary sources are leafy green vegetables (i.e., spinach), nuts, seeds, legumes, and whole grains. Tap and mineral water also have magnesium, but the amounts vary by source and brand.
It is not possible to get a magnesium overdose from diet alone. This is because the kidneys will eliminate any excess amounts during urination.
Supplements and Medications
Magnesium supplements come in various forms, including
- Magnesium citrate
- Magnesium oxide
- Magnesium chloride
- Magnesium glycinate
- Magnesium taurate
- Magnesium malate
Magnesium is also found in over-the-counter (OTC) medications, especially laxatives and antacids. These include:
- Phillips’ Milk of Magnesia, Pedia-Lax (magnesium hydroxide)
- Almacone, Alumox, Maalox Antacid, Mylanta Maximum Strength Liquid Antacid/Anti-Gas (aluminum hydroxide, magnesium hydroxide, simethicone)
- ConRX AR (aluminum hydroxide, magnesium hydroxide)
- Duo Fusion (calcium carbonate, famotidine, magnesium hydroxide)
- Extra-Strength Rolaids (calcium carbonate, magnesium hydroxide): Used for heartburn and acid indigestion
- Other Mylanta formulas besides Maximum Strength
Do Not Exceed Recommended Dosages
If you take supplements or OTC medications, follow the product’s labeling or your healthcare provider’s instructions. Do not take more than the recommended daily amounts.
Who Is More at Risk of Toxic Levels of Magnesium?
Magnesium toxicity is rare because your kidneys help rid the body of excess magnesium. An overdose might occur in someone with poor kidney function, especially if they take medications that contain high levels of magnesium or are taking supplements.
Toxic levels may occur in people who have been taking high doses of magnesium supplements for long periods. Risks are also higher for people with heart problems or gastrointestinal diseases.
A pregnant person who is being treated for preeclampsia (high blood pressure in pregnancy) is at risk for hypermagnesemia if they have been prescribed a high dose to prevent seizures. But this is rare because the magnesium is prescribed for a short period, usually less than 24 hours. A healthcare provider will also monitor you for signs of toxicity during treatment.
People who take laxatives and antacids for extended periods may have an increased risk for hypermagnesemia. Lower amounts and doses of these medicines are generally not dangerous, and the body will usually flush them out with urination and bowel movements.
However, larger doses of laxatives and antacids (more than 5,000 mg per day) can lead to magnesium toxicity. Accidental poisonings can occur when a child or adult ingests too much of these products. While rare, such excessive amounts of magnesium in the body could be fatal.
When to Seek Medical Help
If you think you or someone else might be experiencing symptoms of a magnesium overdose, seek medical attention. This is especially important if you have been taking high doses of magnesium supplements, have a kidney disorder, or have another chronic disease.
How a Magnesium Overdose Is Treated
The first treatment for magnesium toxicity is to stop taking supplements or medicines containing magnesium. Magnesium levels can decrease within a day or two after supplements or magnesium-containing medicines have been stopped. With lower levels, symptoms should improve.
A person with severe hypermagnesemia is often treated with calcium gluconate with an intravenous (IV) drip (through a vein in the arm) to block any toxic effects of the magnesium.
Diuretics (medicines that cause the kidneys to excrete excess fluid through urination) might also be given orally or by IV to help increase urination and help the body filter out the excess magnesium levels.
If you have a kidney disorder, your kidneys cannot process magnesium efficiently. In this case, severe hypermagnesemia will need to be treated with dialysis to clear the magnesium.
What Is Kidney Dialysis?
Kidney dialysis is a process of removing excess water and toxins from the kidneys. It uses a filtering machine that removes waste and fluid from the blood and then returns the filtered blood back to the body.
Why Do People Take Magnesium?
You can take magnesium supplements to meet your daily magnesium requirements. A healthcare provider might prescribe supplements if you have a magnesium deficiency.
You should talk to your healthcare provider before starting a supplement. They can assess your blood magnesium levels and advise you whether it is safe to take supplements based on your unique health situation.
Research shows that around half of Americans do not get enough magnesium in their diets. This can lead to uncomfortable symptoms and severe health problems.
Fatigue, loss of appetite, muscle cramps, weakness, and stiffness are early signs of low magnesium levels, or a magnesium deficiency, but these symptoms can worsen if not treated. Severe symptoms of a deficiency include abnormal heart rhythms and seizures.
The Office of Dietary Supplements at the National Institutes of Health recommends the following dietary allowances for magnesium for adults:
- Adult females age 19–30: 310 mg
- Adult females age 31 and older: 320 mg
- Adult males age 19–30: 400 mg
- Adult males age 31 and older: 420 mg
- During pregnancy: 350–360 mg
- People who are while lactating and nursing: 310–320 mg
Magnesium recommendations for children are much lower, as follows:
- Birth to 6 months old: 30 mg
- 7–12 months old: 75 mg
- 1–3 years old: 80 mg
- 4–8 years old: 130 mg
- 9–13 years old: 240 mg
- 14–18 years old: 410 mg for boys; 360 mg for girls
- Pregnant teens: 400 mg
- Lactating and nursing teens: 360 mg
A Note on Sex and Gender Terminology
Verywell Health acknowledges that sex and gender are related concepts, but they are not the same. To reflect our sources accurately, this article uses terms like “female,” “male,” “woman,” and “man” as the sources use them.
It is important to check with a healthcare provider to see whether these supplements are recommended for you and what level will be safe to take. Also, magnesium might interact with medications, including bisphosphonates (used to treat osteoporosis) and antibiotics, reducing the absorption of these medications.
Magnesium is a vital element for your overall health and well-being. But too much of it could lead to health problems, including digestive troubles, low blood pressure, and an irregular heartbeat.
Magnesium toxicity and overdose are rare. However, some people have a higher risk, including people with impaired kidney function and those taking high-dose magnesium supplements or magnesium-containing medications (such as antacids or laxatives) for long periods. You cannot overdose on magnesium from diet.
Severe hypermagnesemia could be fatal in someone with a kidney disorder. However, early treatment can improve outcomes. Treatment includes stopping supplements, intravenous calcium gluconate, diuretics, and dialysis in people with impaired kidney function.
If you are taking magnesium supplements and suspect you are experiencing magnesium toxicity, you should seek medical help immediately. You should not start magnesium supplements without first talking to your healthcare provider.
You can get magnesium from your diet. Supplements might help you meet your daily recommended amounts or correct a magnesium deficiency.
Read the original article on Verywell Health.