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Magnesium

Supportive Care

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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.

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Possible side effects

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).

Possible side effects of hypermagnesemia

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

Symptoms of an allergic reaction include: rash, hives, itching, chills, fever, headache, muscle ache, shortness of breath, coughing, tightness in the throat, swelling of the face or neck.

Not all patients who take magnesium will experience these side effects. Common side effects are bolded, but there may be others. Please report all suspected side effects to your doctor or pharmacist.

Find more information on side effects.

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Tips for patients and families

Be sure to discuss all questions and instructions with your doctor or pharmacist. 

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.

Hypermagnesemia can occur:

  • 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.

Magnesium at home:

  • 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.
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Always check the medication label. Many medicines look the same. Do not take any new medicine, including over-the counter medicines or supplements, without checking with your doctor or pharmacist. Talk to your doctor or pharmacist about what to do in the case of a missed dose, allergic reaction, or medical emergency. 

This information is not intended to be a complete guide and is not a substitute for talking with your provider. Medicine names, appearance, formulas, or availability may vary by clinic location. Always follow the instructions given by your care team.

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Reviewed: June 2024