What are the symptoms of too much magnesium in the body?

October 1, 2025 •

3 min read

While excessive intake of magnesium from food is highly uncommon, consuming very high doses from supplements or certain medications can lead to a condition known as hypermagnesemia. It is critical to understand the signs and what are the symptoms of too much magnesium in the body to prevent potential health complications.

Quick Summary

This article outlines the causes, symptoms, and risk factors associated with hypermagnesemia. It covers the progression from mild digestive issues to severe cardiovascular and neurological complications, emphasizing the importance of monitoring intake, especially for individuals with kidney problems.

Key Points

Hypermagnesemia is Rare: Excessive magnesium levels (hypermagnesemia) are uncommon in healthy individuals with normal kidney function, as the kidneys effectively excrete the excess.
Supplements are a Primary Risk: Overdoses almost always result from taking too many magnesium-containing supplements, laxatives, or antacids, not from dietary intake.
Kidney Disease is a Major Risk Factor: Individuals with chronic or acute kidney disease are at the highest risk for hypermagnesemia because their kidneys cannot properly remove surplus magnesium.
Symptoms Vary by Severity: Symptoms range from mild effects like nausea, diarrhea, and weakness to severe issues such as low blood pressure, respiratory depression, and cardiac arrest as blood magnesium levels rise.
Prompt Medical Attention for Severe Symptoms: Significant muscle weakness, irregular heartbeat, or difficulty breathing require immediate emergency medical care.
Treatment Depends on Severity: Mild cases may only require stopping intake, while severe cases may need interventions like IV calcium or hemodialysis to correct the imbalance.

Understanding Hypermagnesemia

Hypermagnesemia is the medical term for having an abnormally high level of magnesium in the blood. While magnesium is an essential mineral vital for hundreds of bodily functions, including nerve and muscle function, blood pressure regulation, and energy production, too much of it can disrupt these critical processes. Your body primarily regulates magnesium levels through the kidneys, which filter out excess amounts through urine. For this reason, magnesium toxicity is a rare occurrence in healthy individuals but becomes a significant risk for those with impaired kidney function.

Causes of High Magnesium Levels

Magnesium overdose is most often caused by excessive intake from supplements or medications, rather than from food sources. The risk is particularly high for individuals with compromised kidney function. Common causes include:

Kidney Failure: The most prevalent cause, as malfunctioning kidneys cannot effectively excrete excess magnesium.
Overuse of Supplements and Medications: Taking very high doses of magnesium-containing laxatives or antacids can overwhelm the body’s excretory system.
Intravenous Magnesium: An overdose can occur when magnesium is administered intravenously, such as for the treatment of eclampsia during pregnancy.
Certain Medical Conditions: Conditions like hypothyroidism and Addison's disease can also contribute to elevated magnesium levels.

Spectrum of Symptoms by Severity

The severity of hypermagnesemia symptoms depends on the concentration of magnesium in the blood. Symptoms often progress from mild to moderate to severe as magnesium levels rise. It is important to note that individuals with mild hypermagnesemia may be asymptomatic.

Mild Symptoms (Serum magnesium: <7 mg/dL)

Nausea and vomiting
Diarrhea
Facial flushing or redness
Headache
Drowsiness and lethargy
General weakness

Moderate Symptoms (Serum magnesium: 7–12 mg/dL)

Low blood pressure (hypotension)
Decreased or absent deep tendon reflexes
Worsening confusion and sleepiness
Slow heart rate (bradycardia)
Blurred vision
Bladder paralysis

Severe Symptoms (Serum magnesium: >12 mg/dL)

Muscle flaccid paralysis
Slow, shallow, or difficult breathing (respiratory depression)
Significant drop in blood pressure
Abnormal heart rhythm (arrhythmia)
Prolonged PR interval and widened QRS complex on an ECG
Coma
Cardiac arrest

Understanding Magnesium Toxicity Levels


Symptom Severity	Serum Magnesium Levels (mg/dL)	Primary Manifestations
Mild	<7	Nausea, vomiting, diarrhea, flushing, headache, lethargy
Moderate	7–12	Low blood pressure, reduced reflexes, confusion, slow heart rate
Severe	>12	Flaccid muscle paralysis, respiratory depression, arrhythmia, coma, cardiac arrest

When to Seek Medical Attention

If you are taking magnesium supplements or medications and experience persistent or worsening symptoms like nausea, diarrhea, or unusual weakness, it is wise to consult a healthcare provider. Immediate emergency medical attention is necessary if symptoms progress to severe stages, such as:

Significant muscle weakness or paralysis
Difficulty breathing or slow breathing
Irregular or very slow heartbeat
Severe confusion or loss of consciousness

Treatment and Prevention

In mild cases of hypermagnesemia where kidney function is normal, simply stopping the intake of magnesium supplements or medications may be sufficient to resolve the issue. However, more serious cases require medical intervention.

Intravenous (IV) Calcium: Calcium can temporarily counteract the neuromuscular and cardiovascular effects of excess magnesium.
Diuretics and Saline: For patients with adequate kidney function, IV fluids and loop diuretics like furosemide can increase magnesium excretion through the kidneys.
Dialysis: For patients with severe hypermagnesemia or kidney failure, hemodialysis may be necessary to rapidly clear magnesium from the blood.

Preventing hypermagnesemia primarily involves careful supplement use, especially for those with pre-existing conditions. Always follow recommended dosages, and for those with kidney disease, avoid over-the-counter medications and supplements containing magnesium unless explicitly advised by a doctor. A balanced diet rich in magnesium, like leafy greens and nuts, does not typically lead to excess, as the kidneys are efficient at regulating levels. More information on magnesium intake can be found on the Office of Dietary Supplements at the National Institutes of Health.

Conclusion

While a magnesium overdose from food is highly unlikely, excessive intake from supplements and medications, particularly in individuals with compromised kidney function, can lead to hypermagnesemia. The symptoms of too much magnesium in the body can range from mild gastrointestinal distress to severe and life-threatening cardiovascular and neurological complications. Recognizing these symptoms and understanding the risks is crucial for safe supplementation. Consulting a healthcare provider before starting any high-dose magnesium regimen, especially with underlying health conditions, is the most effective preventative measure against magnesium toxicity.

Frequently Asked Questions

The primary cause of magnesium overdose, or hypermagnesemia, is typically excessive intake from supplements or magnesium-containing medications like laxatives and antacids, especially in individuals with impaired kidney function.

Yes, severely high magnesium levels can be dangerous and even fatal. While mild cases might only cause discomfort like diarrhea and nausea, very high concentrations can lead to cardiac arrest, coma, and respiratory failure.

The first or mildest symptoms of too much magnesium often include diarrhea, nausea, stomach cramps, and general lethargy.

It is extremely rare to get too much magnesium from a balanced diet, as healthy kidneys are highly effective at filtering and removing any excess magnesium ingested from food.

Individuals with acute or chronic kidney disease are at the highest risk for magnesium toxicity because their kidneys cannot efficiently excrete surplus magnesium, leading to a buildup in the blood.

Treatment varies by severity. For mild cases, stopping the source of magnesium is often enough. Severe cases may require intravenous (IV) calcium to counteract the effects, diuretics, or dialysis to remove the excess magnesium from the blood.

The Tolerable Upper Intake Level for supplemental magnesium for most adults is 350 mg per day. It is important not to exceed this amount unless specifically directed and monitored by a healthcare professional.