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What is magnesium?

Magnesium is a mineral that the body needs to function properly. Staff members take blood samples to check the amount of magnesium in the body. If the level is too high or too low, the staff may make changes to medicines or fluids that the patient is receiving.

Hypomagnesemia (not enough magnesium in the blood)

Hypomagnesemia can occur:

  • When you take certain medicines (cisplatin, amphotericin B, cyclosporine)
  • If your kidneys are not working well
  • When you have a loss of body fluids from excessive vomiting, diarrhea, or NG drainage
  • If you have diabetic ketoacidosis or pancreatitis.

Possible side effects of hypomagnesemia

  • Muscle weakness, tremors, twitching
  • Feeling depressed, agitated or confused
  • Cardiac arrhythmias
  • Decreased calcium and potassium in the blood

Staff members can give you magnesium to increase the amount of this mineral in the blood. It is available as a 140-mg capsule, a 400-mg tablet, a white liquid that can be taken by mouth, and as a clear liquid that can be given into a vein (IV).

Hypermagnesemia (too much magnesium in the blood)

Hypermagnesemia occurs when the kidneys are not working well or if the patient has taken in too much magnesium. Staff members will give the patient large amounts of IV fluids to flush the magnesium out of the body.

Possible side effects of hypermagnesemia

  • Low blood pressure
  • Nausea or vomiting
  • Feeling sleepy
  • Heart arrhythmias

Special instructions for magnesium

  • Some antacids contain magnesium (Phillips’® Milk of Magnesia, magnesium hydroxide). Be careful in taking these if you have kidney problems or are already taking another form of magnesium.
  • Please talk to the doctor or nurse if you think you are having symptoms of hypomagnesemia or hypermagnesemia. If you are in the local area call 595-3300. If you are outside the Memphis area, dial toll-free 1-866-2STJUDE (1-866-278-5833), and press 0 once the call is connected.


This document is not intended to take the place of the care and attention of your personal physician or other professional medical services. Our aim is to promote active participation in your care and treatment by providing information and education. Questions about individual health concerns or specific treatment options should be discussed with your physician.

St. Jude complies with health care-related federal civil rights laws and does not discriminate on the basis of race, color, national origin, age, disability, or sex.

ATTENTION: If you speak another language, assistance services, free of charge, are available to you. Call 1-866-278-5833 (TTY: 1-901-595-1040).

ATENCIÓN: si habla español, tiene a su disposición servicios gratuitos de asistencia lingüística. Llame al 1-866-278-5833 (TTY: 1-901-595-1040).

تنبيه: إذا كنت تتحدث باللغة العربية فيمكنك الاستعانة بخدمات المساعدة اللغوية المتوفرة لك مجانا. .يرجى الاتصال بالرقم. 5833-278-866-1  (الهاتف النصي: 1040-595-901-1).