Magnesium is a mineral involved in over 300 biochemical reactions, supporting nerve and muscle function, blood glucose control, blood pressure regulation, energy production, and protein and DNA synthesis. Many individuals turn to magnesium supplements to support overall health or address specific deficiencies. While magnesium from food sources poses no risk of overdose in healthy individuals, excessive intake from supplements can lead to adverse effects.
Recognizing Excessive Magnesium
Hypermagnesemia, a condition where blood magnesium levels are too high, often first appears as gastrointestinal discomfort, including nausea, vomiting, diarrhea, and abdominal cramping. Individuals might also experience facial flushing, lethargy, or dizziness.
As magnesium levels continue to rise, more pronounced symptoms can emerge. These may include muscle weakness, decreased reflexes, confusion, sleepiness, low blood pressure, irregular heartbeat, headaches, and bladder paralysis. Severe hypermagnesemia, though rare in those with healthy kidney function, presents with serious complications such as difficulty breathing, profoundly low blood pressure, severe muscle flaccid paralysis, and irregular heart rhythms that can progress to cardiac arrest or coma. Blood magnesium concentrations typically need to exceed 1.74–2.61 mmol/L (approximately 4 mg/dL) for symptoms to appear, with very severe effects generally occurring above 12 mg/dL.
Factors Leading to Overdose
An overdose of magnesium primarily occurs due to excessive intake from dietary supplements. The Recommended Dietary Allowance (RDA) for adult men ranges from 400 to 420 milligrams daily, and for adult women, 310 to 320 milligrams per day. The Tolerable Upper Intake Level (UL) for supplemental magnesium for healthy adults is typically 350 milligrams per day, though recent evaluations suggest up to 500 milligrams may be well tolerated.
Impaired kidney function is a significant factor in hypermagnesemia. Healthy kidneys filter and excrete excess magnesium, but in individuals with compromised function, such as chronic kidney disease, this capacity is reduced, leading to buildup even with moderate supplement intake.
Certain forms of magnesium are also more likely to cause gastrointestinal issues. Forms like magnesium citrate, oxide, hydroxide, sulfate, carbonate, and chloride are known for their laxative effects due to osmotic activity in the intestines, drawing water into the bowel and stimulating motility. This can lead to diarrhea, which can be a sign of excessive intake.
Emergency Actions and Prevention
If symptoms of a magnesium overdose are suspected, especially severe ones like difficulty breathing, extreme muscle weakness, or an irregular heartbeat, it is important to seek immediate medical attention. Contacting a healthcare professional or emergency services is advisable, particularly if someone has been taking high doses of magnesium supplements, has a known kidney disorder, or if symptoms are persistent. Early diagnosis and intervention can help manage the condition and prevent serious complications.
Preventative measures are important for safe magnesium supplementation. Individuals should always consult a healthcare professional before starting any new supplement, particularly if they have pre-existing health conditions like kidney disease or are taking other medications. Adhering to the recommended dosages on supplement labels and not exceeding the established tolerable upper intake levels unless specifically advised by a doctor is important.
Prioritizing dietary sources of magnesium, such as green leafy vegetables, nuts, seeds, whole grains, and legumes, can help meet daily requirements without the risks associated with high-dose supplements. Magnesium supplements can interact with certain medications, including some antibiotics and bisphosphonates, potentially affecting their absorption or efficacy. Taking magnesium supplements with food can help minimize gastrointestinal upset.