Though unlikely, you can overdose on magnesium.
More Info: The likelihood of magnesium toxicity due to dietary intake of magnesium is practically nonexistent, but there are some behaviors that can lead to magnesium overdose, especially if you have compromised kidney function.
A healthy adult needs to consume between 270 and 400 mg of magnesium per day, depending on weight. While very few people in the Western world suffer from a true magnesium deficiency, most do not consume enough magnesium in their diets to satisfy their daily requirements. The risk of consuming enough magnesium in your diet to risk toxicity is negligible.
It is possible to risk magnesium overdose if you take supplemental magnesium. Magnesium supplements are not recommended for infants or children unless prescribed by a physician. Healthy adults should limit supplementation to 350 mg of magnesium or less per day. Both milk of magnesia and epsom salts are extremely magnesium dense. It is possible to overdose on magnesium when using them as laxatives, antacids, or tonics. To limit your risk of magnesium overdose, use these products only as directed.
Symptoms of Magnesium Toxicity
Because of the risks of magnesium toxicity, you should check with your doctor before taking supplemental magnesium. Nausea and diarrhea are common side effects of magnesium, and may not indicate a problem, but you should check with your doctor if you experience these symptoms after beginning a supplemental magnesium regimen. Rarer side effects include dizziness, flushing, muscle paralysis, and breathing problems. Symptoms of magnesium overdose include blurred or doubled vision, dizziness, drowsiness, change in frequency of urination, vomiting, low heart rate, severely lowered blood pressure, calcium deficiency, mental confusion, coma, and death. Because the kidneys work to flush magnesium and other minerals out of the body, the risk of magnesium overdose greatly increases with impaired kidney function.
Treatment for Magnesium Overdose
The treatment for hypermagnesemia, or the presence of too much magnesium in the bloodstream, depends on the severity of the case. First, the source of the toxicity must be identified and eliminated. Then, calcium chloride can be administered to remove magnesium from the blood. Cardiovascular support may be necessary during the treatment. If the hypermagnesemia is severe, temporary dialysis may be necessary to remove the excess magnesium from the bloodstream.
Elevated magnesium levels can interfere with the absorption of calcium. Magnesium also interacts with some medications.