Magnesium for Dogs: Is It Helpful?

Dogs can receive magnesium, but it should only be started after your vet recommends it. Magnesium is an important mineral that dogs need for normal body function, but dogs who have a complete and balanced diet should get enough from their food. Regular supplementation in healthy dogs is not a good idea because it could result in a dog receiving too much magnesium. 

Instead, magnesium is usually recommended if:  

• Your dog has low magnesium on blood tests  
• Your dog is hospitalized and needs the additional support  
• You provide a homemade diet that doesn’t have enough magnesium included  
• Your dog has a disease or takes medication that affects magnesium levels  

Magnesium is an important electrolyte that helps the body’s cells, nerves, muscles, and heart work normally. Low levels can affect nerve, muscle, and heart function, and dogs may show weakness, trembling, wobbliness, depression, exaggerated reflexes, muscle stiffness, and abnormal heart rhythms.  

In critically ill dogs with electrolyte imbalances, low magnesium can occur alongside low potassium and calcium (other important electrolytes).  

The clearest benefit of magnesium supplementation is correction of a documented deficiency. The main goal in giving magnesium is to restore normal mineral balance when a veterinarian has confirmed that magnesium is low.  

Magnesium can also be part of a vet-directed nutrition plan. Mineral intake, including magnesium, is sometimes adjusted in therapeutic diets for specific conditions.  

Balanced mineral intake is important because too much of one mineral can interfere with others. For example, excessive calcium or phosphorus supplementation can decrease magnesium absorption. 

Too much magnesium can lead to serious problems, especially if a dog has kidney disease or poor intestinal movement that interferes with normal magnesium elimination.  

Signs of excess magnesium include:  

• Nausea  
• Vomiting 
• Weakness  
• Slow heart rate  
• Slow reflexes  
• Respiratory depression  
• Paralysis  
• Coma 
• Cardiac arrest, possibly leading to death 

Give magnesium only if you are directed to do so by your veterinarian. If your vet thinks your dog needs magnesium supplementation, they will tell you exactly what form and how much to give.  

If your dog needs support, your vet may prefer a diet plan or a supplement that fits the full nutrition plan rather than a stand-alone product.  

Be sure your vet knows about any medications your dog takes, especially diuretics or digoxin, which could alter magnesium levels.  

Dogs with kidney disease are at higher risk for magnesium buildup in the body. If your dog has kidney disease or if your vet is already monitoring their electrolytes, magnesium should be used only with close supervision and follow-up testing.  

If your dog gets into a magnesium supplement or starts acting weak, wobbly, sleepy, or sick to their stomach after taking magnesium, call your veterinarian, an emergency hospital, or The Pet Poison Helpline (855-764-7661) right away.  

High magnesium levels can affect breathing and heart function and cause serious consequence, so consider it an emergency.  

What are signs that my dog may have low magnesium? 

Low magnesium levels can cause weakness, trembling, wobbliness, depression, overactive reflexes, muscle pain, and an abnormal heart rhythm. If you notice these signs, contact your veterinarian or an emergency hospital right away. 

Do most dogs need a magnesium supplement? 

No. Dogs eating a complete and balanced diet rarely have a magnesium deficiency. Magnesium should never be supplemented without veterinary guidance, because high levels can lead to serious health problems.  

Is magnesium safe for dogs with kidney disease? 

No, not without veterinary guidance. Kidney disease can lead to high magnesium levels, and extra magnesium can become dangerous if the kidneys can’t eliminate the excess. 

Can low magnesium develop with other health problems? 

Yes. Severe malnutrition, intestinal disease that interferes with nutrient absorption, drugs that affect kidney function, and diabetes can potentially cause low magnesium levels. Low magnesium is also common in critically ill dogs with other electrolyte imbalances.  

Should I give magnesium if my dog seems anxious or restless? 

No, do not assume magnesium is the answer. Magnesium should only be used to correct a deficiency that has been diagnosed by your vet or as part of a vet-directed nutrition plan. It should not be used to address behavior changes.