From Dog

Hypermagnesemia is an electrolyte disorder of dogs characterized by a serum magnesium level > 2.5 mg/dL.

The converse is hypomagnesemia.

At high levels, magnesium acts as a calcium channel blocker and may have deleterious effects on the cardiac conduction, including ventricular arrhythmias and the blunting of responses to epinephrine[1].

Although this is a relatively rare electrolyte disturbance (due to the renal ability to excrete magnesium), it can occur in dogs with:

Specific clinical signs usually do not accompany this electrolyte disorder but symptoms may include weakness, hypotension, respiratory depression, apnea and loss of deep tendon reflexes[3].

ECG examination usually reveals prolonged PR intervals, widening QRS complexes and heart block.

Diagnosis is readily determined on blood electrolyte testing and treatment of underlying renal disease and use of parenteral calcium supplements.


  1. Barros LF & Pileggi F (1991) The antiadrenergic effects of hypermagnesemia: an experimental study. Braz J Med Biol Res 24(1):29-33
  2. de Laforcade AM et al (2005) Biochemical analysis of pericardial fluid and whole blood in dogs with pericardial effusion. J Vet Intern Med 19(6):833-836
  3. Martin LG (1998) Hypercalcemia and hypermagnesemia. Vet Clin North Am Small Anim Pract 28(3):565-585