Magnesium: Benefits, Side Effects, Dosage, Interactions

This supplement may help relax nerves and muscles

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Magnesium is a mineral that's needed for your overall physical health. About half of the magnesium in your body is found in your bones. The rest supports cell function throughout the body.

Among other things, magnesium plays a key role in muscle function, heart rhythm, blood pressure, and blood sugar level. Magnesium also is important to your immune system and keeps it working well.

You probably get enough magnesium from the foods you eat, like nuts and grains, but supplements may be helpful for people with a few specific conditions.

This article explains some of the health benefits of magnesium. It offers information about taking supplements, including what to look for. It also presents possible side effects and drug interactions.

Health Benefits of Magnesium

Like sodium and potassium, magnesium is an electrolyte that the body needs for various functions.

Everyone needs adequate levels of magnesium, and most people get them. Supplementation may be beneficial for people with conditions such as restless legs syndrome and irritable bowel syndrome (IBS).

Nerve and Muscle Excitability

Magnesium is often used to help people whose neuromuscular (nerve and muscle) systems aren't working as well as they should. These systems become overexcited by chemical messages and related stimuli. This can cause an abnormal, excessive response from their muscles.

This common in people who use stimulant medications. It can show up as muscle twitches. It also may cause people to clench their jaws or gnash their teeth. That's often the case for people who find this happens while they're sleeping at night. Some researchers recommend magnesium teas or tablets to help with symptoms of teeth grinding, also known as bruxism.

Magnesium also may help with restless legs syndrome (RLS). With this condition, people have an annoying urge to move their legs, again often at night. Oral supplements were found to improve the symptoms of RLS in a study of 100 patients with type 2 diabetes.

Not all research is clear on the health benefits of magnesium, though. Scientists who conducted a 2019 review of eight different studies found no significant benefit from giving magnesium to people with RLS. They were unable to confirm that magnesium is effective and its role remains unclear.

Irritable Bowel Syndrome

Some studies suggest that using a mineral water rich in magnesium sulfate can improve the frequency of bowel movements in people who have irritable bowel syndrome with constipation (IBS-C).

This possible laxative effect of magnesium appears to come through two pathways. They are:

  • Muscle relaxation: Magnesium may relax the muscles in the intestines. This can help to establish a smoother flow as the stool passes through the bowels.
  • Stool softener: Magnesium draws water into the intestines, working as an osmotic laxative. This increase in water stimulates bowel motion, or motility. It also softens and increases the size of the stool. This prompts a bowel movement and helps to make stools easier to pass.

Food Sources of Magnesium

The best place to get magnesium is from the food you eat. Pumpkin seeds, for example, contain very high amounts of magnesium—about 152 milligrams (mg) per ounce.

Other good dietary sources of magnesium include:

  • Nuts and seeds like almonds, peanuts, and cashews
  • Beans and legumes such as black beans and lima beans
  • Whole grains, including whole wheat bread, wheat bran, and oatmeal
  • Dark chocolate
  • Leafy greens like spinach, kale, and collard greens

Side Effects and Risks of Magnesium Supplements

Side Effects of Magnesium
Verywell / Cindy Chung

Diarrhea is the most common side effect of taking magnesium supplements. This can lead to:

  • Dehydration
  • Nutritional deficits
  • Weight loss
  • Electrolyte imbalance, with potential effects on heart, muscles, and breathing


Toxic amounts of magnesium can cause problems with the kidneys. It may also cause severe reactions that affect the intestines.

One condition called ischemic colitis can cause permanent damage to the intestines, and it has been linked to magnesium toxicity.

Be sure to read supplement labels carefully to prevent excess intake.

Medication Interactions

Supplemental magnesium may interfere with some of your medications and reduce their effectiveness.

Before starting magnesium, tell your healthcare provider and pharmacist if you are taking any of the following:

Warnings and Precautions

Your kidneys are responsible for clearing magnesium from the blood. For this reason, if you have kidney disease or need dialysis, you should not take supplements unless prescribed by your healthcare provider. Even adding normal amounts of a vitamin or mineral may be toxic.

If you are using magnesium to treat IBS-related constipation, you should know that the same dose of magnesium used to treat constipation is not meant to be used as a dietary supplement.

What Is Hypermagnesemia?

Hypermagnesemia is the abnormal buildup of magnesium in your body. This can happen if your kidneys are impaired. Hypermagnesemia can lead to heart rhythm problems, respiratory distress, and even cardiac arrest,

Dosage and Preparation

The National Institutes of Health (NIH) has published a fact sheet on the recommended daily intake of magnesium, which includes the total amount you should get from foods. The recommended daily allowance is different depending on your age, but in general:

  • Adult females should get between 310 mg and 360 mg a day (more if pregnant or breastfeeding).
  • Adult males should get between 400 mg and 420 mg per day.
  • For children, the daily recommended intake increases with age. Newborns need about 30 mg per day, while older children need up to 240 mg.

You can take magnesium as a vitamin pill or in a prepared liquid form. It also is sold as a powder to mix into a liquid.

Magnesium supplements also are paired with different chemicals. For example, magnesium salt products are absorbed at different rates in the small intestine. This means they may deliver magnesium to the body more slowly. Different dose levels are necessary for the effects to be felt.

Differences in how magnesium products work can make it hard to know if a dose used in a clinical study of one magnesium salt product will have the same effect as a dose of a different mix. Keep this in mind when reading research results and talk to your healthcare provider before taking it.

Choosing a Magnesium Supplement

Start by checking the labels on magnesium packaging. This will allow you to find the active dosage as well as any other ingredients in the product. They may include flavorings, fillers, or binders.

You also want to confirm the product is safe and effective by looking for a product certified by an independent testing organization like ConsumerLab. In 2019, the company investigated dozens of popular magnesium supplements sold on the market and found a few that disintegrated quickly when exposed to moisture.

ConsumerLab also found several that contained harmful amounts of lead, and others that were improperly labeled based on the contents. These third-party test sites can help you to know if you can trust what you see on the label.


Magnesium does a lot of work in your body. This mineral, available from both food and supplements, is necessary for a healthy immune system, proper heart function, and more. Some people take magnesium supplements to treat specific conditions like IBS-C and restless legs syndrome, for which there is some research-based evidence.

But supplements are not for everyone. People who have limited kidney function should avoid taking magnesium because of the risk of toxicity. Other serious side effects include electrolyte imbalances and permanent digestive tract damage.

If you plan to take magnesium, be sure you know what you're getting. It's available in different mixtures and forms that can change its effects. Read product labels and be sure to buy from a reputable store or online provider.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Aguilera SB, Brown L, Perico VA. Aesthetic treatment of bruxismJ Clin Aesthet Dermatol. 2017;10(5):49-55. PMID: 28670358

  2. Metta V, Sampath N, VM R, Iska A. Primary restless legs syndrome in patients with type 2 diabetes mellitus: efficacy of magnesium & co enzyme q10 therapy. Journal of the Neurological Sciences. 2015;357(1):e271. doi:10.1016/j.jns.2015.08.952

  3. Marshall NS, Serinel Y, Killick R, et al. Magnesium supplementation for the treatment of restless legs syndrome and periodic limb movement disorder: A systematic reviewSleep Medicine Reviews. 2019;48:101218. doi: 10.1016/j.smrv.2019.101218

  4. Bothe G, Coh A, Auinger A. Efficacy and safety of a natural mineral water rich in magnesium and sulphate for bowel function: A double-blind, randomized, placebo-controlled study. Eur J Nutr. 2017. 56(2):491-499. doi:10.1007/s00394-015-1094-8

  5. University of Rochester Medical Center. Health encyclopedia: nutrition facts.

Additional Reading

By Barbara Bolen, PhD
Barbara Bolen, PhD, is a licensed clinical psychologist and health coach. She has written multiple books focused on living with irritable bowel syndrome.