How Does Magnesium Citrate Work, and What Happens When You Drink It?

Magnesium citrate is an over-the-counter supplement used to treat constipation.
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Make no mistake: Magnesium is a critical mineral. The electrolyte is required for more than 300 enzymatic reactions in the body, including digestion, blood sugar regulation, blood pressure management and fluid balance, per the National Institutes of Health (NIH).


But there are a handful of different forms of magnesium, and each serves its own functions. "Magnesium glycinate is a very relaxing form of magnesium that is great for sleep, nervous system support and managing anxiety," explains Anna Brown, RD, registered dietitian and founder of the private practice Nutrition Squeezed.

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"Magnesium sulfate is great for muscle relaxation if you have cramps or twitches and also to help your body with detoxification and the biotransformation process."

The main benefit of magnesium ‌citrate‌ supplements is bowel regularity. "Magnesium citrate can act as a laxative so it is used mostly for constipation and to increase bowel motility," Brown says.

Below, nutrition experts highlight everything you need to know about what happens when you drink magnesium citrate.

What Is Magnesium Citrate?

Magnesium citrate is technically a salt that consists of the mineral magnesium and citric acid, per the National Library of Medicine (NLM). It usually comes in powder form to mix with a liquid (like water), as a liquid sold in a bottle or as a tablet (like many other supplements).


"The main reason it's recommended to people is to treat constipation and encourage bowel regularity. In high amounts, it helps with preparation for a bowel procedure like a colonoscopy," Brown explains.

Unlike magnesium glycinate, which is well-absorbed, magnesium citrate isn't readily taken up by the body, so it's not typically used for actually replenishing magnesium stores.


Magnesium Citrate Safety

Though generally considered safe, magnesium citrate isn't recommended for people with diarrhea or electrolyte imbalances.

"Magnesium citrate can have a laxative effect, so for those who are already facing diarrhea or chronic GI issues that can cause loose stools, magnesium citrate could exacerbate that condition," says Amanda Wahlstedt, RD, registered dietitian and founder of the private practice Roots to Leaves.



Others who should avoid the supplement include "those with hyponatremia [or low blood levels of sodium], those on a sodium-restricted diet and those with renal disease or failure, as magnesium citrate can alter electrolyte balance and hydration status," Wahlstedt warns.

Also good to know: Magnesium citrate is meant to be taken for a limited period of time. "It's better as a one-off treatment for occasional constipation or used daily for a short period of time during a treatment protocol when you need to increase bowel motility, as in the case of small intestinal bacterial overgrowth (SIBO)," Brown explains.


The NLM recommends limiting magnesium citrate supplementation to one week unless otherwise instructed by your doctor.


“If you experience chronic constipation that [requires] daily use of a supplement like magnesium citrate, I would recommend additional testing to uncover the root cause of your constipation so it can be reversed,” Brown says.

For example: “Is it methanogen SIBO, low vagal nerve tone, too much or too little fiber, a pelvic floor issue or not enough water? These are all questions you want to ask if you find yourself needing to take a supplement like magnesium citrate on a daily basis just to have a bowel movement.”

How Exactly Does Magnesium Citrate Work in the Body?

"Magnesium citrate is an osmotic laxative, which means it causes water to be retained with the stool instead of getting reabsorbed into the colon," Brown explains. "When water is retained in the stool, it increases the number of bowel movements and also makes bowel movements easier to pass because they are softer."


Immediate Effects

Immediate effects of magnesium citrate typically include looser and more frequent bowel movements. Common side effects of the supplement can also include gas and stomach pain, per Memorial Sloan Kettering Cancer Center.


It's unusual, but if you experience dizziness or nausea after taking magnesium citrate, contact your doctor. These symptoms may be due to hypotension, or low blood pressure, as magnesium assists in lowering blood pressure levels in the body.

Experts say magnesium citrate supplements are best taken with water. "The water and magnesium bind together, creating an ionic magnesium citrate that is better absorbed by the gastrointestinal tract," Wahlstedt says. "This can be done as a magnesium citrate powder mixed into water or as a capsule taken with at least 8 ounces of water."


As for how fast you can expect the supplement to kick in, "generally [magnesium citrate takes] effect 30 minutes to 8 hours after consumption," Wahlstedt says. "However, this [can depend] on the dose taken, the length of time taking it, the reason for taking it and your individual health context."


"For some, it may take repeated doses over a few days to elicit a bowel movement," Brown adds. "If they don't have a bowel movement after taking magnesium citrate for 5 days, I would discontinue [supplementation] and speak with their healthcare provider to find an alternative and to rule out any more serious issues like fecal impaction."

Magnesium Citrate Dosing

The NIH notes that magnesium typically reaches toxic levels in the body only once someone has taken about 5,000 milligrams or more (though we don't recommend inching anywhere close to that dosage level).

Some people may need to surpass the upper limit in order for a bowel movement to occur, Wahlstedt adds. "For this reason, it is important to work with a registered dietitian or doctor to help figure out the right dose for you."

Alternatives to Magnesium Citrate

Recommended alternatives to magnesium will depend on why you're reaching for the mineral in the first place.

"For example, if you're looking to replete magnesium stores, then a magnesium glycinate [supplement] may be a good option, while Epsom salt baths [may be used] as a topical way to absorb magnesium and relax the muscles and body," Wahlstedt says.

If you are turning to magnesium citrate for constipation relief, there are other interventions you may try first:

Drink More Water and Eat More Fiber

Begin by drinking more water and eating more fiber — doing both plays a big role in bowel movement regularity. Fortunately, many magnesium-rich foods, like leafy greens, cashews, Brazil nuts, legumes, pumpkin seeds and whole grains, are also high in fiber.


Give Yourself Time in the Bathroom

Also important: "Give your body the time and space to actually go to the bathroom," Brown says.

"This may sound odd, but we are a culture of 'go go go' and that often makes us actually ‌not‌ go. We need to feel relaxed and safe in order to go to the bathroom, so these practices can be helpful."

When to See a Doctor

If the basics aren't bringing on bowel movements, consider investigating further.

"If someone doesn't see any constipation relief after trying the above techniques for 2 to 4 weeks, I would recommend additional testing or counseling to rule out the underlying cause of constipation before trying too many different supplements," Brown says.

"Once you figure out the root cause of constipation, it's much easier to treat…and manage symptoms."