Magnesium Sulfate: Uses, Recommended Dose & Side Effects

Magnesium sulfate is a medication that is commonly indicated for magnesium deficiency, constipation relief or for muscle pain relief. 

This salt, also referred to as Epsom salt, can be purchased pharmacies in a powder form, used a dietary supplement or added to baths or foot soaks. 

Although magnesium sulfate can be purchased without a prescription, you should only use it as directed by a doctor. Incorrect use can lead to complications, and it is contraindicated for certain populations, like children, pregnant women, diabetics, and people with renal or cardiac disease.

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Common uses

Magnesium sulfate can be prescribed for magnesium deficiencies or to relieve constipation. Because it has laxative and purgative effects, the doctor may prescribe it prior to surgical procedures, radiologic testing or colonoscopies to clean out the intestines.

Magnesium sulfate can also be added to baths or dressings to relieve muscle pain, arthritis or fibromyalgia due to its relaxant effects. 

Can magnesium sulfate cause weight loss?

Magnesium sulfate does not cause weight loss, as it is orally indicated for stool elimination for constipation. 

However, constipation may cause symptoms like bloating or abdominal swelling, and taking this medication can stimulate bowel movements and relieve swelling. This can lead to a false sensation of weight loss. 

It is important to highlight that you should not take magnesium sulfate for weight loss, and that you should only take it as directed by your doctor.

How to take

Magnesium sulfate can be used to relieve constipation by diluting this salt in 250 mL of filtered water. This mixture should be taken on an empty stomach first thing in the morning. 

The recommended dose for intense and immediate laxative purposes 5 to 30 grams per day. This is equivalent to one teaspoon to two tablespoons. Treatment for a magnesium deficiency should be oriented with doses prescribed by a doctor or registered dietitian. 

Magnesium sulfate should be taken as directed by a doctor, without surpassing the prescribed dose. 

This medication can also be added to baths, dressings and foot soaks. 

Possible side effects

The side effects of magnesium sulfate are minimum, but can lead to diarrhea, excess gas, stomach ache, and electrolyte imbalances. These are more likely to emerge if higher doses are used, or if it is used for more than 2 weeks.

High doses can lead to hypermagnesemia or magnesium overdose. These conditions cause symptoms like facial redness, excessive sweating, loss of reflexes, muscular weakness, shallow breathing, coma, respiratory arrest and cardiac arrest. These symptoms should be assessed immediately in an emergency room, as they can be life-threatening. 

Contraindications for use

Magnesium sulfate should not be used by children under 2, pregnant or breastfeeding women, or anyone with a history of kidney problems, cardiac problems, chronic bowel obstruction, Crohn's disease, ulcerative colitis and other intestinal inflammations. 

Magnesium sulfate should not be used by people who take digoxin, nor should it be used for more than 2 weeks.