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Written by leading veterinarians to provide you with the information you need to care for your pets.

Your dog's nutrition is important for a healthy & happy life. petMD experts help you to know what to feed your dog, how much food to feed, and the differences in dog foods, so your dog gets optimum nutrition.
Nutrition Nuggets is the newest offshoot of petMD's Dog Nutrition Center. Each week Dr. Coates will use her expertise and wisdom to blog about the intricacies of dog nutrition.

What is Magnesium and Why is It Important?

October 09, 2015 / (2) comments

Magnesium… You see it listed on dog food ingredient labels and it’s often reported on a patient’s blood work, but what does it do in the body? I confess that I had only the sketchiest of ideas; so I did some research. Here’s what I found.


Magnesium is classified as an essential macromineral. The word “essential” in nutritional circles simply means that the body cannot manufacture it (or manufacture enough of it) to meet the body’s needs. Therefore, it must be included in the diet in sufficient amounts to avoid deficiencies. Macrominerals—calcium, phosphorus, magnesium, sodium, potassium, chloride, and sulfur—are minerals (inorganic nutrients) that the body requires in relatively larger amounts than it does microminerals (e.g., iron, zinc, copper, manganese, iodine, and selenium).


According to Medline Plus:

Magnesium is needed for more than 300 biochemical reactions in the body. It helps to maintain normal nerve and muscle function, supports a healthy immune system, keeps the heart beat steady, and helps bones remain strong. It also helps regulate blood glucose levels and aid in the production of energy and protein. 


Hypermagnesemia (too much magnesium in the body) is not a common problem for dogs, unless they are suffering from chronic kidney failure. If a dog ingests too much magnesium, healthy kidneys are extremely efficient at excreting the excess.


On the other hand, hypomagnesemia (too little magnesium in the body) is seen quite frequently in sick dogs. One study found that 33.6% of critically ill dogs and cats suffered from hypomagnesemia, which tends to develop when a dog has one of the following conditions:

  • Chronic diarrhea
  • Starvation
  • Pancreatic disease
  • Some types of liver disease
  • Diabetes mellitus
  • Treatment with insulin
  • Hyperthyroidism
  • Hyperparathyroidism
  • Acute kidney failure
  • Chronic heart failure
  • Sepsis (an overwhelming bacterial infection)
  • Hypothermia
  • Severe trauma
  • Iatrogenic (the use of some types of IV fluids, diuretics, other drugs, etc.)


Hypomagnesemia is often accompanied by other mineral deficiencies, particularly low calcium and potassium levels. The clinical signs associated with these conditions include:

  • Poor appetite and digestive function
  • Weakness
  • Muscle twitches/tremors
  • Confusion
  • Abnormally strong reflexes
  • Seizures
  • Abnormal heart rhythms
  • Coma


Keep in mind that a dog without any of these symptoms can still have hypomagnesemia. Blood tests for magnesium levels tend to be quite reliable in dogs, although some individuals with normal blood levels (especially low-normal levels) might be whole body magnesium-deficient.


Treatment is simple and involves some form of supplementation—intravenous infusions when a dog’s condition is critical, oral when it is less so. Commercially available dog foods contain enough magnesium for healthy dogs, but if your dog is sick with one of the conditions listed above, magnesium supplementation might be a good idea to prevent or treat hypomagnesemia. The only time that I would worry about giving a dog a magnesium supplement is when he or she is at risk for chronic kidney failure.


Talk to your veterinarian if you think your dog needs a magnesium supplement.



Dr. Jennifer Coates





Hypocalcemia and hypomagnesemia. Dhupa N, Proulx J. Vet Clin North Am Small Anim Pract. 1998 May;28(3):587-608.


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... graduated with honors from the Virginia-Maryland Regional College of Veterinary Medicine in 1999. In the years since, she has practiced veterinary medicine in Virginia, Wyoming, and Colorado. She is the author of several books about veterinary medicine and animal care, including the Dictionary of Veterinary Terms, Vet-Speak Deciphered for the Non-Veterinarian .

Jennifer also writes short stories that focus on the strength and importance of the human-animal bond and freelance articles relating to a variety of animal care and veterinary topics. Dr. Coates lives in Fort Collins, Colorado with her husband, daughter, and pets.