Magnesium Deficiency in Dogs

Magnesium is a mineral needed by every cell in the body and is required for more than 300 biochemical reactions. It is a macro-mineral which means it is needed in greater amounts in the diet, and found in larger amounts in the body. Most magnesium is found in bone (60 percent) and soft tissue (38 percent), and most of the soft tissue magnesium resides in the skeletal muscle and liver. It is second only to pottasium as the most abundant substance in the cell. 

Hypomagnesemia is defined as a serum magnesium levels below the normal canine reference range of 0.7 – 1.1 mmol/L. 

It is required for many metabolic functions, and its role as an activator or catalyst for more than 300 enzyme systems includes formation of the enzymes that involve ATP (adenose triphosphate), which transports chemical energy within cells for metabolism. Since it is so vital for the body, its deficiency(also known as hypomagnesemia) leads to serious health problems. 

Magnesium has a number of important functions. It is necessary for the absorption and proper use of certain vitamins and minerals including Vitamin C, Vitamin E, calcium and phosphorus, sodium, and potassium. It is necessary for proper bone growth and is necessary for the functioning of many enzymes in the body, and production of protein.

Magnesium is an important cofactor in maintaining an electrical balance across membranes. It is also important in the production and elimination of acetylcholine (a neurotransmitter). A low concentration of magnesium in the extracellular fluid (fluid outside the cell) can increase concentrations of acetylcholine at the motor endplates and cause  an involuntary reaction of muscles. Interference with the electrical gradient can result in neuromuscular and heart abnormalities. Magnesium also regulates calcium movement into smooth muscle cells, and is important to contractile strength (the muscle's capability to contract) and to the stability of the surface vessels of the body.

Some of the complications that can occur with hypomagnesemia are alterations of the functions of the skeletal muscles, resulting in tetany (severe muscular pain) and a variety of myopathies (diseases of skeletal muscles); ventricular heart arrhythmias, or torsades de pointes (a tachycardia, or fast heart rhythm that originates in one of the ventricles of the heart), and depolarization of cardiac cells and tachyarrhythmias (fast heart rhythms); resistance to the effects of parathyroid syndrome; an increase in the uptake of calcium into bone; and an increase in the risk of digoxin (digitalis) toxicity.

Common signs and symptoms associated with hypomagnesemia include:


Muscle trembling

Ataxia (muscle incoordination)


Hyperreflexia (overactive reflexes)

Tetany (severe muscle pain)

Behavioral changes

Arrhythmias (abnormal heart rhythms)

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