Excess Magnesium in the Blood in Cats

When magnesium levels become elevated, it causes a condition known as hypermagnesemia. Excess magnesium can negatively affect nervous, respiratory, urinary, and cardiac systems. Very high levels can lead to cardiac arrest, coma, and can be fatal if medical treatment is not received. Successful treatment of excess magnesium in the blood requires correct identification and proper treatment of the underlying cause. Kidney disease, certain medical treatments, and other conditions can affect a cat’s ability to regulate and eliminate magnesium, leading to elevated levels in the blood. 

Magnesium is an essential nutrient and electrolyte that is required for numerous bodily functions. Magnesium is introduced to the body through the diet, and it is often added to pet foods. It is found naturally in fish, leafy greens, whole grains, and other nutrient rich foods. 

Too much magnesium in the blood can affect brain function in cats and other companion animals. This causes issues with many major systems in the body, resulting in a wide range of symptoms related to respiratory and nervous systems, the urinary tract, and the heart. 

Symptoms Include: 

• Vomiting
• Weakness 
• Urolithiasis or urinary stones
• Painful urination
• Changes in behavior
• Depression
• Lack of reflex
• Paralysis
• Trouble breathing
• Slowed pulse rate
• Cardiac arrest
• Shock
• Coma
• Death

Several underlying health conditions could be causing high magnesium levels, such as poor function of bodily systems that regulate or require magnesium, including the digestive, endocrine, and the urinary systems. Excess magnesium can also be caused by administered magnesium or diet. 

Potential Causes Include:

• Poor Kidney Function: Kidney disease or kidney failure impacts the regulation of magnesium. When kidneys don’t function properly, levels can climb. 
• Endocrine Disorders: The endocrine system uses magnesium, reducing levels when it operates normally. 
• Digestive Issues: Constipation and other conditions that slow the digestive system can cause the body to absorb more dietary magnesium than normal. 
• Administered Magnesium: Some medications and intravenous fluids contain magnesium and can result in an overdose of magnesium entering the body. 
• High Magnesium Diet: Certain pet foods and items like fish or leafy greens can contain high magnesium levels. 

Veterinary diagnosis will begin with a physical examination and medical history. Be prepared to discuss your cat’s eating habits, recent medical treatments, and any known issues. Several tests will be required to identify magnesium levels and look for underlying causes. An analysis of blood and urine samples is necessary to identify the amount of magnesium in the cat’s system. Testing of the cat’s kidney function is also needed, as kidney disorders are the most common cause. The results of these tests, along with observation of the clinical signs allow veterinary staff to diagnose the condition. Your veterinarian may also monitor cardiac and respiratory function while your pet is being diagnosed and treated. An electrocardiogram or ECG will check for heart-related issues. X-rays or other imaging techniques may also be employed to observe heart and lung function. 

Medical treatment is required to prevent damage and life-threatening complications related to high magnesium levels. Treatment methods will vary depending on the underlying cause. A combination of treatments to reduce magnesium levels and treat the cause is the most effective approach. The veterinarian will begin by stopping the introduction of magnesium into the cat’s system. Any administered magnesium in medications or fluids will be stopped, and a low magnesium diet may be introduced. Throughout the treatment, veterinary staff will monitor magnesium levels, respiratory function, and cardiac function. Treatment options include:

• Intravenous (IV) Fluids: Fluid therapy, using IV fluids without magnesium, is used to flush magnesium from the system. Therapy will continue until tests indicate levels fall within the normal range. This is a common treatment option and carries a low risk of side effects. 
• Administered Calcium: Adding calcium to your pet’s system promotes magnesium excretion, or the elimination of magnesium. Your cat will be monitored while undergoing calcium therapy to ensure the levels stay within a normal range. Too much calcium in the blood can also cause issues. 
• Kidney Treatments: If impaired function is the cause, proper treatment is necessary to aid kidney performance. Blood filtering and medications are common forms of kidney treatment. Depending on the severity and type of kidney disorder, these treatments may be required indefinitely. 
• Diuretics: This type of medication is used to flush fluids from the system. It works similarly to fluid therapies, but can produce the results faster than fluid alone. Unlike fluid therapy, there is some risk associated with using diuretics. Your veterinarian will determine if the magnesium levels are high enough to warrant the additional risk. 

The earlier diagnosis and treatment of excess magnesium in the blood begins, the better the prognosis. Longer term exposure to elevated magnesium levels can have a permanent effect on impacted bodily systems, and may be fatal. High magnesium levels that are unrelated to kidney disease generally respond well to treatment and most cats will make a full recovery. Kidney related issues may require ongoing treatments. When your pet is able to return home, you will need to monitor closely for recurrence or worsening of symptoms. Return to the veterinarian if your pet does not improve. Encourage fluid intake by making clean water available at all times, and ensure a proper diet for your cat that balances key nutrients, including magnesium, calcium, and phosphorus.