Hypermagnesemia refers to high magnesium levels in the blood. It does not usually cause symptoms, however, it can result in nausea, drowsiness, mental confusion or muscle paralysis.

Hypermagnesemia can be caused by kidney failure, excessive use of magnesium supplements or digestive issues, like colitis. Very high levels that are left untreated can lead to conditions like cardiac arrhythmias, respiratory depression or cardiac arrest.

Treatment for hypermagnesemia is carried out by a general practitioner or registered dietitian, and will vary depending on the underlying cause and patient's symptoms. To correct magnesium levels, your doctor may prescribe IV medications and hemodialysis.

Common symptoms

The main symptoms of hypermagnesemia are:

Nausea
Puffy face
Dizziness, drowsiness or mental confusion
Decreased reflexes
Bladder paralysis
Headache
Constipation
Blurred vision

These symptoms usually occur when blood magnesium levels are above 4 mg/dL, as mildly high levels do not usually cause symptoms and are only discovered during routine blood tests.

When magnesium levels are severely high, or above 12 mg/dL, muscle paralysis, low blood pressure, decreased respiratory rate, coma or cardiac arrest may also occur.

Confirming a diagnosis

Hypermagnesemia is diagnosed by a general practitioner or registered dietitian. They will start by assessing your symptoms and health history.

The doctor may then request blood tests that measure magnesium, potassium, phosphate and calcium levels, in addition to a metabolic panel, arterial blood gas analysis, kidney function tests and an electrocardiogram.

Magnesium reference values

Normal blood magnesium levels in adults are between 1.6 mg/dL and 2.6 mg/dL. Levels are considered high when they are above 2.6 mg/dL.

High blood magnesium levels can be classified as:

Less than 7 mg/dL: Mild hypermagnesemia
Between 7 and 12 mg/dL: Moderate hypermagnesemia
Over 12 mg/dL: Severe hypermagnesemia

Reference values may vary depending on the laboratory and the measurement method used. Results should be interpreted by a doctor alongside with other diagnostic tests.

Possible causes

The most common causes of high magnesium are:

Renal failure;
Use of supplements or medications containing magnesium or lithium;
Gastrointestinal diseases, such as gastritis or colitis;
Hyperparathyroidism;
Tumor lysis syndrome;
Diabetic ketoacidosis;
Rhabdomyolysis.

Pregnant women with preeclampsia or eclampsia may also develop temporary hypermagnesemia due to the use of high doses of magnesium in treatment.

In these cases, high levels are usually caught by the obstetrician and tend to correct themselves shortly thereafter, when the kidneys start to eliminate excess magnesium.

Conditions caused by high magnesium

The main diseases that can develop as a result of untreated hypermagnesemia are:

1. Low blood pressure

High magnesium, especially values above 12 mg/dL, can reduce blood pressure greatly.

This is because magnesium reduces peripheral vascular resistance and promotes vasodilation, leading to low blood pressure. This should be treated urgently in a hospital setting.

2. Arrhythmias

High magnesium levels can alter electrical conduction in the heart and cause arrhythmias. It can also lead to a sharp decrease in heart rate, which is referred to as bradycardia.

3. Cardiac arrest

Changes in the electrical conduction in the heart caused by very high magnesium levels (generally above 15 mg/d) can lead to cardiac arrest.

4. Respiratory depression

High magnesium levels can also cause respiratory depression, which can present with symptoms such as difficulty breathing or weak and slow breathing. High magnesium levels circulating in the body can weaken the respiratory muscles.

In more severe cases, very high magnesium levels can cause respiratory arrest.

5. Intestinal paralysis

High magnesium levels can also slow down or paralyze intestinal muscles, resulting in paralytic ileus or even a bowel obstruction in the most severe cases.

6. Coma

High magnesium levels can affect brain functioning, leading to drowsiness or mental confusion. In more severe cases, it can develop into a coma.

Treatment options

Treatment for hypermagnesemia should be guided by a general practitioner or registered dietitian, and is aimed at correcting blood magnesium levels to normal levels.

High magnesium levels caused by kidney failure can be treated with hemodialysis.

Hypermagnesemia from excessive magnesium intake, the person can be treated by discontinuing or reducing the dose of magnesium supplements, and by removing high-magnesium foods from the diet.

In more severe cases, treatment should be performed in a hospital setting, and usually involves IV calcium gluconate or diuretics, depending on the cause of hypermagnesemia.

Hypermagnesemia often presents with abnormal potassium and calcium levels, and therefore treatment may also involve correcting other mineral levels.

Hypermagnesemia: Symptoms, Normal Levels & Causes