Why Is My Dog Or Cat's Blood Magnesium Level Low Or High ?













Ron Hines DVM PhD

To see what normal blood and urine values are, go here

For an explanation of causes of most abnormal blood and urine tests, go here

To see how tests are grouped, go here

Your Pet’s Blood Magnesium Level = Mg

After sodium (Na+), potassium (K+) and calcium (Ca2+), magnesium (Mg2+) is the most common positive ion (cation), in your pet’s blood stream. It is required for many enzyme-based reactions to occur. Within the pet's cells themselves, it is second only to potassium in abundance. The normal diet of dogs and cats contains plenty of magnesium because meat is such a rich source.

Approximately fifty percent of the magnesium in your pet's body is found in its bones. Mot of the other half is found inside the cells of its body. Only about 1% of you’re dog or cat 's magnesium is found in its blood. Its body works hard to keep that amount constant. So when the vet says your pet is deficient in magnesium, based on a blood test, that doesn't necessarily mean that all its magnesium reserves are low.

To little blood magnesium (hypomagnesemia) is considerably more common in dogs and cats than too much magnesium (hypermagnesemia).



Reasons Why Your Pet’s Magnesium Levels Could Be Low (Hypomagnesemia) :

Pets that are critically ill from any cause can have fluctuations in their blood cations – including magnesium.

Intestinal disease that prevents proper magnesium absorption or sustained (long term) diarrhea can also lower your pet's blood magnesium level. It can also shift out of the blood in pancreatitis. Failing kidneys that compensate by producing large amounts of dilute urine can also allow too much magnesium to escape from your pet's blood.

Failure to eat/starvation and inappropriate or bizarre diets can cause your pet's magnesium level to be low.

Uncontrolled diabetes that causes excessive urination can lower magnesium levels. Hyperthyroidism, low parathyroid gland activity (hypoparathyroidism) have also caused blood magnesium levels to be low.

Pets that receive excessive amounts of diuretics (eg furosemide given for heart disease) , intravenous feeding in hospitalized pets or pets given large amounts of magnesium-free IV fluid can also experience low blood magnesium. (In humans, aminoglycosides [like gentamycin], digoxin, amphotericin B and cyclosporine have all been associated with low blood magnesium level. I do not know if that occurs in pets as well.)

Reasons Why Your Pet ’s Magnesium Levels Might Be High (Hypermagnesemia) :

Kidney shut-down (ogilouric renal failure), Addison’s disease, over-use of magnesium-containing supplements or laxatives can all increase blood magnesium. Urinary tract blockages can also cause higher-than-normal magnesium. When a large amount of your pet's muscle tissue is injured (necrosis) , large amounts of magnesium are released. That can also cause blood magnesium levels to be temporarily high.

A hemolized blood sample can give falsely-elevated magnesium level.

Complimentary Tests :

BUN, Creatinine, complete urinalysis all for evidence of kidney disease, Free T4 level, ACTH test for Addison’s Disease, Blood calcium/ PTH levels