What Causes High Magnesium Levels? An In-Depth Look at Hypermagnesemia

November 16, 2025 •

3 min read

Hypermagnesemia, or high magnesium levels in the blood, is a relatively rare electrolyte imbalance that can have serious health consequences, most often linked to kidney dysfunction. Understanding what causes high magnesium levels is crucial for those with underlying health conditions or who use magnesium-containing products frequently.

Quick Summary

This article explains the causes of hypermagnesemia, a rare condition where excess magnesium builds up in the blood. It details how kidney failure, medications like antacids and laxatives, and certain endocrine disorders contribute to this electrolyte imbalance.

Key Points

Kidney Failure is a Primary Cause: The most common cause of high magnesium levels is compromised kidney function, as healthy kidneys regulate magnesium excretion effectively.
Medications Pose a Risk: Excessive or long-term use of magnesium-containing antacids, laxatives, or certain drugs like lithium can cause magnesium levels to rise, especially with underlying kidney issues.
Endocrine Disorders Play a Role: Conditions such as Addison's disease and hypothyroidism can disrupt the body's natural hormone balance and impair magnesium regulation.
Supplements Can Overload the System: While dietary magnesium is safe, megadoses from supplements can overwhelm the body's ability to excrete the mineral, particularly in those with renal impairment.
Cellular Damage Increases Levels: Massive cellular breakdown from conditions like tumor lysis syndrome and rhabdomyolysis can release large amounts of intracellular magnesium into the bloodstream.
High Magnesium Is Preventable: Identifying risk factors, including underlying health conditions and medication usage, is key to preventing hypermagnesemia.

The Role of the Kidneys in Magnesium Regulation

Your body maintains a delicate balance of magnesium, with the kidneys playing the central role in regulating its excretion. Normally, the kidneys filter out any excess magnesium, effectively preventing high levels from accumulating. However, when kidney function is compromised, this filtration process fails, allowing magnesium to build up in the bloodstream and leading to hypermagnesemia. For this reason, acute or chronic kidney disease is the most common cause of high magnesium levels.

Medications and Supplementation That Cause High Magnesium Levels

While the kidneys are typically efficient at excreting magnesium, introducing large amounts of magnesium into the body can overwhelm their capacity, especially in individuals with pre-existing kidney issues.

Over-the-Counter and Prescription Medications

Certain medications are notable contributors to hypermagnesemia:

Antacids and Laxatives: Many common over-the-counter products for heartburn or constipation contain magnesium hydroxide. Long-term or excessive use can lead to magnesium toxicity, particularly in older adults or those with impaired kidney function.
Epsom Salts: These are chemically known as magnesium sulfate. Ingesting large quantities or absorbing it through the skin via baths can elevate magnesium levels, especially with existing renal impairment.
Lithium: Used in psychiatric treatment, lithium can reduce magnesium excretion by the kidneys, potentially causing hypermagnesemia.
Intravenous (IV) Magnesium: Medically administered magnesium, such as during the treatment of preeclampsia or eclampsia, can cause dangerously high levels if not carefully monitored.

Dietary Supplements

While dietary intake alone is unlikely to cause hypermagnesemia in healthy individuals, taking high-dose magnesium supplements, particularly with reduced kidney function, increases the risk of toxicity. Always consult a healthcare provider before starting a new supplement regimen.

Endocrine and Other Health Conditions

Beyond kidney disease and medication use, several other underlying health issues can cause or contribute to high magnesium levels.

Endocrine Disorders

Addison's Disease (Adrenal Insufficiency): The adrenal glands produce hormones that regulate various bodily functions, including electrolyte balance. Dysfunction can lead to poor magnesium excretion.
Hypothyroidism: An underactive thyroid can reduce the kidneys' ability to filter electrolytes, potentially leading to increased magnesium concentration.

Cellular Breakdown and Metabolic Issues

Diabetic Ketoacidosis (DKA): This severe complication of diabetes can cause an extracellular shift of magnesium, leading to a temporary increase in serum magnesium levels.
Tumor Lysis Syndrome: When cancer cells break down rapidly, they release their intracellular contents, including magnesium, into the bloodstream.
Rhabdomyolysis: This condition involves the rapid breakdown of damaged muscle tissue, which releases intracellular electrolytes like magnesium and potassium.

Comparison of Causes and Risk Factors


Cause Category	Risk Factor Profile	Mechanism of Hypermagnesemia
Kidney Disease	Most common and significant cause, affecting individuals with chronic or acute renal failure.	Reduced kidney filtration and excretion of excess magnesium from the body.
Medication Use	Individuals using magnesium-containing antacids, laxatives, or specific drugs like lithium.	Overwhelming the kidneys' capacity to excrete magnesium, or impacting renal function directly.
Endocrine Disorders	Patients diagnosed with adrenal insufficiency or hypothyroidism.	Hormonal imbalances that interfere with normal magnesium regulation and excretion.
Cellular Damage	Conditions like tumor lysis syndrome, rhabdomyolysis, or severe acidosis.	Release of large quantities of intracellular magnesium into the bloodstream.
Excessive Supplementation	Individuals taking high-dose oral or intravenous magnesium, especially with impaired kidneys.	Excessive intake overloads the body's natural excretory mechanisms.

Conclusion

While a rare condition in those with healthy kidneys, understanding what causes high magnesium levels is critical for prevention and management, particularly for individuals with kidney disease. The primary risk factors are impaired renal function, overuse of magnesium-containing medications, and the presence of underlying health conditions that affect electrolyte balance. By recognizing these causes, individuals can work with healthcare providers to monitor their levels and minimize risks.

The Crucial Role of Renal Function

It is important to reiterate that for most healthy people, consuming magnesium-rich foods or standard supplements is not a significant risk factor for developing hypermagnesemia. The kidneys are remarkably efficient at maintaining homeostasis. The danger arises when kidney function is already impaired and the body's ability to excrete this mineral is diminished, or when massive amounts are introduced iatrogenically. For at-risk individuals, regular blood testing and cautious use of magnesium products are essential preventative measures. For more in-depth medical guidance, consult resources such as the MSD Manual, which provides detailed information on managing hypermagnesemia.

Frequently Asked Questions

For individuals with normal kidney function, it is highly unlikely to develop high magnesium levels (hypermagnesemia) from diet alone, as the kidneys are very efficient at excreting excess magnesium.

Yes, taking high-dose magnesium supplements, especially in cases of compromised kidney function, can lead to hypermagnesemia. It is crucial to follow recommended dosages and consult a doctor, especially if you have renal issues.

The most common cause of hypermagnesemia is kidney failure, where the kidneys cannot effectively filter and excrete excess magnesium from the blood.

Many common antacids and laxatives contain magnesium. With long-term or excessive use, particularly in patients with kidney problems, this high intake can overwhelm the body's excretory capacity, leading to a buildup of magnesium.

Early or mild symptoms of hypermagnesemia can include nausea, vomiting, flushing, and weakness. As levels increase, more severe neurological and cardiac symptoms can occur.

Yes, treatment with lithium-based medications can reduce the kidney's ability to excrete magnesium, which can lead to elevated magnesium levels.

Yes, severe hypermagnesemia is a serious and potentially fatal condition. It can cause significant neuromuscular, respiratory, and cardiac problems if left untreated.