Magnesium Sulfate Benefits, Dosage and Side Effects - Dr. Axe

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Magnesium Sulfate for Both Constipation & Muscle Relief


Magnesium sulfate

Magnesium sulfate is one type of magnesium supplement that can help treat symptoms of magnesium deficiency like muscle cramps, fatigue and irritability — plus other common health problems, too, such as constipation.

Virtually every part of our bodies — including our cells, nerves, muscles, bones and hearts — require a steady supply of the nutrient magnesium to maintain normal functioning. Magnesium is an essential mineral, the fourth most abundant in the human body, and also an electrolyte that is present in the body in large amounts. It plays a role in numerous functions, like heart health, muscle contractions and more.

While some people are able to obtain enough magnesium from eating a healthy diet, the majority of adults are actually believed to be deficient. Having low levels of magnesium (called hypomagnesemia) can negatively affect how your nervous system, cardiovascular system and digestive systems work, which is why supplementation is now widely recommended — including magnesium sulfate supplements.

What Is Magnesium Sulfate (What Is It Used For?)

Magnesium sulfate is a type of magnesium supplementThe chemical formula for magnesium sulfate is MgSO4, meaning it can be broken down into magnesium and sulfate, which is a combination of sulfur and oxygen. 

Magnesium sulfate is available over-the-counter in a few different forms, including capsules, soaking salts and also as an IV. Another name for this product is Epsom salt, a brand name for a type of magnesium salt that seeps through the skin.

How does magnesium sulfate work? It works in several ways, such as by increasing the amount of water in the intestines, causing vasodilation (widening blood vessels and improving blood flow) and blocking the entry of calcium into synaptic endings, which alters neuromuscular transmission. It’s effective at preventing certain types of seizures and convulsions because it blocks transmission between nerves and muscles.

What is magnesium sulfate good for? The No. 1 reason this product is recommended by health care providers is to reverse low amounts of magnesium in the blood (in other words, magnesium deficiency).

Another common reason people use this type of magnesium is to treat constipation, since it works as a natural laxative. Other uses include decreasing muscle soreness, promoting relaxation and improving skin health.

According to an article in the Journal of midwifery and Women’s Health, this type of magnesium is one of the most commonly used medications in obstetric practices today.

By boosting your magnesium levels you can support vital functions, such as muscle control, energy production, electrical impulses, and regulation of calcium and vitamin D levels in the body. Not only can you soak in magnesium sulfate salts in a bath, but you can also find this product in many hair and skin care products due to its hydrating qualities.

Health Benefits and Uses

1. Helps Treat Constipation

Magnesium sulfate is used to help produce a bowel movement when someone is seeking constipation relief. It usually works within 30 minutes to six hours after taking it by mouth.

The most common form used for promoting a bowel movement is magnesium sulfate powder, which is mixed with water. Taking magnesium in this form has an osmotic effect and causes water to be retained in the intestinal lumen. This hydrates stools and makes it easier to pass.

A combination of sodium sulfate, potassium sulfate and magnesium sulfate can also be used to cleanse the colon before a colonoscopy. For this purpose, one serving is usually taken early in the evening before colonoscopy (10 to 12 hours before the second dose), and then another serving is taken in the morning before the test.

2. Can Relieve Muscle Tension and Pain

The body can absorb magnesium through the skin via the process of transdermal absorption. What does magnesium sulfate feel like? Adding Epsom salt to your bath can help relax your muscles, reduce inflammation and decrease joint pain, including aches associated with arthritis or bone pain.

For people who struggle with stiffness, muscle spasms, cramps or ongoing foot pain, soaking effected body parts in a magnesium soak bath with Epsom salts can reduce discomfort and help improve range of motion, including of the ankles, knees and feet. It’s also a good option for people who experience restless leg syndrome, which can make it hard to get quality sleep.

3. Promotes Relaxation

Taking a warm bath with magnesium at night is a simple way to help relieve stress. While magnesium deficiency can increase feelings of anxiety and tension, magnesium sulfate has the opposite effect. It can boost your ability to cope with stress thanks to its effects on neural excitability and blood pressure.

It may even help manage symptoms associated with depression and neuropsychiatric disorders. For those looking to unwind with help from magnesium, this homemade healing bath salts recipe is an easy way to utilize magnesium.

Can you get high off magnesium sulfate? No, despite what some people claim on the internet, using this product will not get you “high,” but it may naturally help you feel more calm.

4. Decreases Bloating and Water Retention

Magnesium sulfate combined with water causes reverse osmosis. This pulls salt and excess fluids out of your body, helping relieve swelling. Using magnesium sulfate capsules or Epsom salts may help discourage water retention and promote elimination, decrease bloating and help to reduce edema tied to inflammation.

5. Can Help Improve Blood Sugar Levels

Magnesium deficiency is believed to be a contributing factor in metabolic syndrome, heart disease, high blood pressure, muscular problems and diabetes. According to Diabetes Self Management website, people with diabetes/insulin resistance are more likely than those without to be low in magnesium — plus high blood glucose levels can further increase the loss of magnesium in the urine.

6. Treats Symptoms of Preeclampsia and Eclampsia During Pregnancy

Preeclampsia and eclampsia can be life-threatening complications that sometimes lead to seizures, stroke, multiple organ failure, and death of the woman and/or baby. Magnesium sulfate has been utilized for seizure control since the 1920 and today is used via IV to prevent seizures associated with preeclampsia (pregnancy-related hypertension), and to control seizures due to eclampsia.

The Collaborative Eclampsia Trial, an international, randomized, placebo-controlled study conducted in 1995, found that women treated with magnesium sulfate had about a 50 percent to 70 percent lower occurrence of convulsions than those treated with other medications, including diazepam and phenytoin. Because it can help prevent seizures during pregnancy, this treatment has also been found to reduce the risk of maternal death.

Additionally, magnesium sulfate is used to lower the risk of an unborn, preterm fetus developing neurological issues and conditions, including cerebral palsy (the leading cause of neurologic impairment in young children).

How does magnesium sulfate provide neuroprotection? While the exact mechanism isn’t entirely understood, research suggests that magnesium can help stabilize circulation and blood pressure/blood flow to the brain and prevent excitatory injury by stabilizing neuronal membranes and blockade of excitatory neurotransmitters, such as glutamate.

Does magnesium sulfate cause hyperreflexia (a condition in which your nervous system overreacts to stimuli and spikes blood pressure)? No. In fact, studies have found beneficial effects of magnesium sulfate on hyperreflexia during labor in patients with spinal cord injuries.

Most hyperreflexia patients receive magnesium intravenously during high-risk labor under the supervision of a doctor in order to prevent complications like changes in blood pressure and heartbeats, constriction of  blood vessels, and changes in the body’s autonomic functions and reflexes.

7. Supports Respiratory Health

Because magnesium relaxes bronchial smooth muscles and has other functions, in supplement form it can be used to manage asthma attacks and improve lung function and breathing. While it’s not typically the first treatment that will be used, magnesium sulfate is sometimes given intravenously or through a nebulizer (a type of inhaler) to treat serious and sudden asthma attacks.

It’s believed to work by inhibiting calcium influx, decreasing histamine release, stopping release of chemicals that cause inflammation, inhibiting chemicals that cause muscle spasms, and by having other effects on nerves and receptors.

Who Should Take It

Magnesium sulfate products are indicated for those with magnesium deficiency, especially if low magnesium levels lead to symptoms like changes in cardiovascular function, muscle spasms, headaches, etc. Obtaining adequate magnesium is important for maintaining normal function of your muscles and nerves, normal blood sugar levels and blood pressure, and for preventing serious cardiovascular and neurological problems.

Certain people can benefit from taking magnesium sulfate more than others. You may be more likely to have magnesium deficiency if:

  • You regularly use diuretics or proton pump inhibitors
  • You don’t eat a balanced diet that includes fruits and veggies
  • You have a history of alcoholism
  • You have a medical condition that causes frequent diarrhea/vomiting or stomach/intestinal absorption problems, such as inflammatory bowel diseases like Crohn’s or ulcerative colitis
  • You have poorly controlled diabetes

Certain people should avoid using this type of magnesium product or only do so with help from their doctors, including anyone with severe stomach pain, nausea, vomiting, a perforated bowel, a bowel obstruction, severe constipation, colitis, toxic megacolon or neuromuscular diseases.

Make sure that magnesium sulfate supplements are safe for you to use if you have a history of diabetes, kidney disease, an eating disorder, high potassium, a neuromuscular disease or if you’ve been told to follow a low-magnesium diet.

Side Effects & Drug Interactions

Magnesium sulfate side effects can potentially include:

  • Diarrhea
  • Stomach pains or indigestion
  • Symptoms of an allergic reaction, like hives, difficult breathing, swelling of your face, etc.
  • Rectal bleeding
  • Drowsiness
  • Edema

Magnesium sulfate can interact with many medications, including certain antibiotics, thyroid medications, bisphosphonates and tetracycline drugs. In order to prevent drug interactions, avoid taking other medicines within two hours before or after you take magnesium sulfate.

Is magnesium sulfate dangerous if you take too much?

Magnesium overdose is also called magnesium toxicity. It’s very important to follow dosage directions for magnesium sulfate carefully because taking or using too much can cause serious, even life-threatening side effects. Rarely serious complications can occur like respiratory paralysis, hypothermia, low blood pressure, changes in cardiac function, and dangerous changes in potassium and calcium levels in the blood.

What is the first sign of magnesium toxicity? Some include changes in your breathing, slowed reflexes, dizziness due to low blood pressure and digestive issues like nausea.

Is it safe to use magnesium sulfate in pregnancy?

Sometimes administration of magnesium sulfate is used off-label to treat preterm labor, which some studies show is safe, although there’s still risks involved. This use of magnesium sulfate is off-label, which means that it is not an FDA-approved use of the drug. According to the FDA, “Administration of magnesium sulfate injection to pregnant women longer than 5–7 days may lead to low calcium levels and bone problems in the developing baby or fetus, including thin bones, called osteopenia, and bone breaks, called fractures.”

While most magnesium supplements can be safely taken by pregnant women, it’s not exactly known whether taking magnesium sulfate for more than five to seven days or on an ongoing basis during pregnancy or while breastfeeding is safe. Generally speaking it should only be used when clearly needed and when other products are not effective. It’s usually best to use other forms of magnesium in low doses while pregnant to avoid side effects.

Magnesium supplements shouldn’t be used in place of medications that are prescribed for you by your doctor. Always talk to your doctor if you notice potentially serious side effects, like rectal bleeding, changes in heartbeat rhythms, etc. If magnesium sulfate doesn’t cause a bowel movement within one to two days, stop taking it and visit your doctor to rule out other health problems.

Use caution when taking high doses of magnesium in order to prevent magnesium sulfate toxicity. Always get help if you develop symptoms of a magnesium overdose, such as slowed heartbeat, severe drowsiness, dizziness, confusion, muscle weakness or loss of consciousness.

Supplement and Dosage Guide

The recommended daily allowance (RDA) of magnesium is 350 to 420 milligrams per day for most adults, which can be obtained through a combination of foods and supplements. The best way to avoid an overdose in magnesium is to follow dosage directions and avoid taking more than 500 milligrams or so of magnesium a day.

Magnesium sulfate is taken in two primary ways: orally as a supplement taken by mouth or used as Epsom salts in a soaking bath. Sometimes it’s also given intravenously when someone is severely deficient.

  • To take magnesium sulfate by mouth: Dissolve one dose of magnesium sulfate in eight ounces of water, stir this mixture and drink it right away. Some people also like to add juice or lemon juice to help enhance the flavor. If you take capsules by mouth, don’t crush or chew the pills, since this can affect how much magnesium is released into your body at one time.
  • To use magnesium sulfate as an Epsom salt soak: Dissolve Epsom salt in a bath (you can also use a large bowl of water or a bucket if only soaking your feet), then sit in the mixture and soak for about 20 to 40 minutes. By simply soaking your feet or entire body in a bath containing Epsom salts, you can increase internal levels of magnesium naturally without taking magnesium supplements. Read the product’s directions to know how much Epsom salt to use per gallon of water. To keep the product from going bad, make sure to store it in a dry, room temperature location.
  • To treat mild to severe magnesium deficiency: The current protocol for administration of magnesium sulfate is one gram given intravenously (IV) over six hours for four doses for mild deficiency or five grams over three hours for severe deficiency. Maintenance is then between 30–60 mg/kg/day in IV form.
  • Magnesium sulfate for preeclampsia: To control eclampsia during pregnancy, four to five grams can be administered via an IV, followed by a maintenance dose that depends on the individual’s reaction.

How long does magnesium sulfate stay in your system?

Magnesium sulfate usually takes effect immediately and can stay in your system for at least several hours and up to about 24 hours. After treatment with high doses of magnesium, levels usually return to normal within a few days.

You can lower your chances of experiencing diarrhea or a stomachache when taking magnesium if you consume it with meals and also drink plenty of water.

Make sure to drink lots of fluids while using magnesium sulfate, since it works in part by absorbing water in the digestive system. Remember that while getting extra magnesium from supplements can be helpful for some people, it’s still important to eat a healthy diet that provides magnesium. Magnesium-rich foods include leafy green veggies, avocados, bananas, beans, whole grain cereals, cocoa and nuts.

How does magnesium sulfate compare to other magnesium supplements?

Magnesium supplements are available in a variety of forms. The absorption rate and bioavailability of magnesium supplements differs depending on the kind. Overall, more research is needed to determine the comparative bioavailability.

Highly absorbable, magnesium glycinate is less likely to cause laxative effects than some other magnesium supplements.

Magnesium citrate may have a laxative effect in some cases when taken in high doses, but is otherwise safe to use for improving digestion and preventing constipation. Typically used as a laxative and remedy for acid reflux, magnesium oxide may be taken in higher doses than other forms since its not absorbed as well.

An oil form of magnesium, magnesium chloride can be applied to skin but also taken in capsule or tablet form, or even used as bath salts like magnesium sulfate. It’s also given to people who have digestive disorders that prevent normal absorption of magnesium from their food. Athletes sometimes use magnesium oil to increase energy and endurance, to dull muscle pain, and to heal wounds or skin irritation.

Magnesium malate combines the essential mineral magnesium and malic acid, and is more often used for fatigue, weakness, muscle pain and low energy.

Final Thoughts

  • Magnesium sulfate is a type of magnesium supplement that is made with the mineral magnesium plus sulfur and oxygen. It’s also called Epsom salt.
  • Magnesium sulfate is commonly taken internally for constipation relief or applied to the skin.
  • Its other benefits are known to include a boost in magnesium levels, stress reduction, toxin elimination, pain relief and blood sugar improvement. This product is also a remedy for arthritis joint pain and inflammation. It can be used to treat breathing problems like asthma and help women prevent or treat preeclampsia and eclampsia.
  • Be sure to drink lots of fluids while using magnesium sulfate, since it works in part by absorbing water in the intestines.
  • Magnesium overdose is also called magnesium toxicity. It’s very important to follow dosage directions for magnesium sulfate carefully because taking or using too much can cause serious, even life-threatening side effects.

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