Do You Poop Out Excess Magnesium? Understanding Your Body's Mineral Balance

January 6, 2026 •

3 min read

According to the National Institutes of Health, healthy kidneys are highly effective at eliminating surplus magnesium from food through urine. So, do you poop out excess magnesium? The answer is nuanced, involving both your digestive system and kidneys working in tandem to maintain healthy mineral levels.

Quick Summary

The body regulates magnesium levels through the kidneys and intestines. While kidneys excrete excess via urine, unabsorbed supplemental magnesium can draw water into the colon, causing diarrhea.

Key Points

Dual Excretion Pathway: The body removes excess magnesium through both the kidneys (via urine) and the intestines (via feces).
Kidneys Are Primary Regulators: For a healthy individual, the kidneys control systemic magnesium levels by excreting any absorbed excess into the urine.
Diarrhea is a Laxative Effect: Unabsorbed magnesium from high-dose supplements draws water into the colon, causing a laxative effect that results in diarrhea.
Supplemental vs. Dietary Differences: Excess magnesium from food is primarily handled by the kidneys and is not a health risk, while excess from supplements can cause significant gastrointestinal issues.
Risk of Toxicity: The risk of dangerous magnesium overload (hypermagnesemia) is very low from food but increases with high-dose supplements, particularly in people with impaired kidney function.
Form Matters: Certain forms of magnesium, such as citrate and oxide, are less absorbed and more likely to cause diarrhea than more bioavailable forms like glycinate.

How the Body Regulates Magnesium

Magnesium homeostasis is a tightly controlled process involving a dynamic interplay between your intestines, kidneys, and bone stores. The body works to keep serum magnesium concentrations within a narrow, healthy range. When you consume magnesium, it is primarily absorbed in the small intestine, although some occurs in the colon. The absorption rate varies based on your body's current needs, with a higher percentage absorbed when intake is low and a lower percentage absorbed when intake is high.

The Kidney's Role in Excretion

For a healthy individual, the kidneys are the primary organ responsible for regulating excess magnesium. When serum magnesium levels are sufficient, the kidneys simply filter out the excess and eliminate it through urine. This is why magnesium from food sources rarely causes issues—the kidneys are efficient enough to handle any surplus without problems. However, people with impaired kidney function are at a much higher risk of hypermagnesemia, or magnesium toxicity, because their kidneys are less able to remove the mineral from the body. In these cases, even moderate supplemental intake can be dangerous.

The Intestine's Role and the Laxative Effect

While the kidneys handle systemic regulation, the intestine is responsible for dealing with the magnesium that is not absorbed in the first place. A normal diet provides magnesium that is absorbed at an efficient rate, but high doses from supplements or medications can overwhelm the body's absorptive capacity. When unabsorbed magnesium salts remain in the intestine, they exert an osmotic effect, drawing water into the bowel. This increases intestinal motility and results in a laxative effect, manifesting as looser, more frequent, or watery stools. Forms of magnesium such as citrate, oxide, and hydroxide are particularly known for this effect, which is why they are used in laxative and antacid products.

Excess Magnesium from Food vs. Supplements

The way your body handles excess magnesium differs significantly depending on the source. Understanding this is crucial for safe supplementation and digestive health.

Dietary Magnesium

Your kidneys regulate excess amounts. When you eat magnesium-rich foods like leafy greens, nuts, seeds, and whole grains, your body absorbs only what it needs, and any surplus is excreted via urine.
Risk of overdose is very low. It is extremely difficult to consume a dangerous amount of magnesium from food alone.

Supplemental Magnesium

Intestinal effects are common. High doses, especially from poorly absorbed forms, lead to a laxative effect as unabsorbed salts draw water into the colon.
Risk of toxicity is higher. Overdosing is possible with supplements, particularly in those with impaired kidney function, and can lead to serious health issues.

How Your Body Processes Excess Magnesium


Process	Excretion Mechanism	Role in Regulation	Typical Cause of Excess Excretion
Renal Excretion	Via urine	Primary systemic regulator for absorbed magnesium.	Any excess magnesium beyond the body's needs (including from food and absorbed supplements).
Fecal Excretion	Via feces (bowel movements)	Handles unabsorbed magnesium directly from the gut.	High-dose supplements and medications with poor bioavailability.

Managing Your Magnesium Intake

To avoid unwanted side effects like diarrhea, it's important to be mindful of your magnesium intake, especially from supplements. Start with a low dose and gradually increase it to find what works for you. Taking supplements with food can also help minimize digestive distress. If you consistently experience diarrhea, you may need to switch to a different form of magnesium that is better absorbed, such as magnesium glycinate or malate. Always consult a healthcare provider before starting a new supplement, especially if you have an underlying health condition like kidney disease.

Conclusion

So, do you poop out excess magnesium? The answer is that you excrete it through both your urine and feces, with each route playing a distinct role. Your kidneys are the main regulator, efficiently clearing surplus absorbed magnesium to maintain your mineral balance. However, unabsorbed magnesium from high-dose supplements and medications passes through the digestive tract and can cause a laxative effect, leading to excretion via feces. This dual excretion process is a testament to the body's robust ability to manage its mineral needs and protect itself from overload. Magnesium - Health Professional Fact Sheet | ODS NIH

Frequently Asked Questions

No, it is extremely rare to get magnesium toxicity from food alone. In healthy individuals, the kidneys are highly efficient at eliminating excess magnesium absorbed from a normal diet through urine.

Magnesium supplements, especially high-dose or poorly absorbed forms like citrate and oxide, can cause diarrhea. Unabsorbed magnesium salts in the intestine have an osmotic effect, pulling water into the bowel and speeding up bowel movements.

The kidneys play the primary role in regulating the body's magnesium levels. When you have enough magnesium, the kidneys excrete the excess via urine. When levels are low, they conserve magnesium by limiting excretion.

Yes, forms of magnesium that are more easily absorbed by the body, such as magnesium glycinate and magnesium malate, are less likely to cause a laxative effect compared to forms like magnesium oxide and citrate.

Individuals with impaired kidney function are at a significantly higher risk for magnesium overdose because their body cannot effectively filter and excrete the mineral. Long-term, high-dose supplement use also increases risk.

To minimize digestive upset, start with a low dose and increase it slowly, take your supplement with food, and consider switching to a more absorbable form like magnesium glycinate if you experience issues.

While tap, mineral, and bottled waters can contain varying amounts of magnesium, the kidneys handle any excess in healthy individuals, and it is not a common cause for concern.