Which Magnesium Is Hard on the Stomach? Forms to Avoid for Digestive Upset

October 31, 2025 •

4 min read

According to the National Institutes of Health, a significant portion of the population has inadequate magnesium intake, yet finding the right supplement can be a challenge. Discovering which magnesium is hard on the stomach is crucial for those who experience unwanted digestive issues from common forms like oxide and citrate.

Quick Summary

Magnesium oxide and citrate are most likely to cause digestive distress like diarrhea due to poor absorption and osmotic effects. Gentler forms include magnesium glycinate and malate.

Key Points

Magnesium Oxide: This is one of the most common forms known for causing significant digestive upset, including diarrhea, due to its poor absorption.
Magnesium Citrate: Often used as a laxative, this form can cause significant digestive distress for those not seeking that effect due to its osmotic action.
Gentler Forms Exist: Magnesium glycinate, malate, and taurate are highly bioavailable and less likely to cause stomach issues, making them ideal for sensitive digestive systems.
Cause of Upset: Poorly absorbed magnesium salts draw water into the intestines, causing an osmotic effect that leads to diarrhea and cramping.
Minimize Side Effects: Take supplements with food, start with a low dose, and split your daily intake to improve tolerance.
Check Your Goals: If correcting a deficiency, opt for a highly absorbable form. If treating constipation, a more potent form like citrate may be appropriate.

The Harsh Culprits: Forms of Magnesium Hard on the Stomach

Not all magnesium supplements are created equal. The form, or the compound to which magnesium is bound, dictates how well it's absorbed by the body. Poorly absorbed forms are notorious for drawing water into the intestines, causing the osmotic effect that leads to a laxative response and general gastrointestinal (GI) discomfort. For individuals with a sensitive stomach, this can be a major issue. While some may seek this effect for constipation relief, those supplementing for general health may find it distressing.

Magnesium Oxide: The Most Common Offender

Magnesium oxide is one of the most widely available and cheapest forms of magnesium, often found in drugstore supplements and antacids. However, its low bioavailability—meaning the body absorbs very little of it—makes it particularly hard on the digestive system. Because so much of the supplement remains unabsorbed in the gut, it creates a powerful osmotic effect, pulling excess water into the colon and leading to diarrhea, cramping, and upset stomach. For this reason, magnesium oxide is often used as a short-term laxative rather than for correcting a long-term deficiency.

Magnesium Citrate: Effective but Potent

Magnesium citrate is magnesium bound to citric acid. It is well-known for its effectiveness as an osmotic laxative, prescribed for treating occasional constipation or as a bowel prep for medical procedures like colonoscopies. While generally well-absorbed, its primary function is to draw water into the intestines to soften stools and stimulate bowel movements. For those who do not want a laxative effect, magnesium citrate can be unpleasantly harsh on the stomach and lead to diarrhea, especially in higher doses.

Other Forms to Approach with Caution

Magnesium Carbonate: This compound, also used as an antacid, can cause gastrointestinal discomfort and has a laxative effect, especially in higher doses. It's effective at neutralizing stomach acid but can result in diarrhea if not properly tolerated.
Magnesium Chloride: Although it is absorbed relatively well, magnesium chloride can still cause digestive side effects like diarrhea and stomach upset in some individuals.
Magnesium Sulfate (Epsom Salt): Used primarily for baths, ingesting magnesium sulfate is typically discouraged due to its potent, often aggressive, laxative action.

Why Certain Magnesium Forms Cause Digestive Upset

The underlying reason for digestive distress from certain magnesium supplements is tied to their chemical structure and bioavailability. Magnesium salts that are not readily absorbed in the small intestine travel to the colon. Here, they exert an osmotic effect, drawing water into the intestines. This excess water softens the stool and increases the volume and frequency of bowel movements. For people with particularly sensitive digestive systems, this process can lead to significant discomfort, including bloating and cramping, even at moderate doses. The side effects are a direct result of the supplement's poor absorption rather than an allergic reaction.

The Gentle Alternatives: Magnesium Forms for Sensitive Stomachs

If you have a sensitive stomach or wish to avoid the laxative effect, several forms of magnesium are known for their high bioavailability and gentleness.

Magnesium Glycinate

This highly absorbable form of magnesium is chelated, meaning it is bound to the amino acid glycine. This chelation process makes it very well-tolerated by the digestive system and minimizes the laxative effect associated with other forms. Often recommended for those seeking magnesium for relaxation, sleep, or mood support, it is a top choice for individuals with sensitive stomachs.

Magnesium Malate

Magnesium malate, bound to malic acid, is another form known for its excellent digestive tolerance and high bioavailability. It is often used to support muscle function and energy production, and its gentle nature makes it a good option for those requiring higher doses without the worry of GI upset.

Magnesium Taurate

Combining magnesium with the amino acid taurine, this form is well-tolerated and often recommended for cardiovascular health. It is a good option for those who experience digestive issues with other forms.

Comparison Table: Hard on the Stomach vs. Gentle


Form of Magnesium	Bioavailability	Common Use	GI Side Effects
Magnesium Oxide	Very Low	Antacid, laxative	High likelihood of diarrhea, cramping, upset stomach
Magnesium Citrate	Good	Laxative, deficiency	High likelihood of diarrhea, cramping (intended use)
Magnesium Carbonate	Low	Antacid, laxative	Can cause diarrhea and gas
Magnesium Chloride	Good	Deficiency, topical	Can cause diarrhea in some individuals
Magnesium Glycinate	High	Relaxation, sleep, mood	Low likelihood of GI issues, well-tolerated
Magnesium Malate	High	Energy, muscle function	Low likelihood of GI issues, gentle
Magnesium Taurate	High	Cardiovascular health	Low likelihood of GI issues, well-tolerated

Tips for Taking Magnesium Without Stomach Issues

If you find yourself struggling with digestive side effects from your magnesium supplement, consider these practical tips:

Take with Food: Consuming your supplement with a meal can significantly reduce the risk of digestive upset.
Start with a Low Dose: If you are new to magnesium, begin with a lower dose and gradually increase it to allow your body to adjust.
Split the Dose: Instead of taking your full dose at once, try splitting it into smaller amounts throughout the day.
Switch Forms: If you are taking a form known to cause GI distress, consider switching to a gentler, more bioavailable form like magnesium glycinate or malate.

Conclusion: Choosing the Right Magnesium for You

Choosing the right form of magnesium is essential for a positive supplementation experience, especially for those with sensitive stomachs. Forms like magnesium oxide and citrate, while useful for specific purposes like constipation, are often too harsh for regular, long-term use. For better absorption and minimal digestive side effects, magnesium glycinate and magnesium malate are superior choices. Always consult a healthcare professional before beginning any new supplement, particularly if you have underlying health conditions or take other medications. For more authoritative information on magnesium, see the NIH Fact Sheet on Magnesium.

Frequently Asked Questions

Magnesium can cause stomach issues because certain forms are poorly absorbed by the small intestine. These unabsorbed magnesium salts draw water into the intestines, creating an osmotic effect that results in loose stools, cramping, and other digestive discomforts.

Magnesium citrate is intended to be a laxative, so it is often harsh on the stomach, causing a strong laxative effect. The severity of the effect depends on the dose and individual sensitivity. Lower doses can be better tolerated, but those with sensitive digestion may want to avoid it.

For a sensitive stomach, magnesium glycinate and magnesium malate are generally the best choices. They are highly bioavailable, meaning the body absorbs them efficiently, minimizing the amount left in the intestines to cause an upset stomach.

To reduce the risk of an upset stomach, take your magnesium supplement with a meal, not on an empty stomach. You can also start with a lower dose and gradually increase it, or split your daily dosage into smaller amounts taken throughout the day.

Magnesium oxide is not necessarily 'bad,' but it is not the most effective form for correcting a magnesium deficiency due to its low absorption rate. It is better suited for its primary use as a short-term laxative or antacid, not for long-term supplementation.

Yes, poorly absorbed magnesium can lead to bloating and gas. The unabsorbed salts in the intestines can cause fermentation and other digestive disturbances. Opting for a more bioavailable form like magnesium glycinate can help reduce these symptoms.

Magnesium glycinate is specifically known for being gentle on the stomach and is far less likely to cause diarrhea than forms like oxide or citrate. However, taking very high doses of any supplement can potentially cause digestive issues, so it's important to stick to recommended amounts.

While it's ideal to get nutrients from food, many people do not consume enough magnesium-rich foods. A supplement may be necessary, but choosing a well-tolerated form is important to avoid digestive side effects. Good food sources include leafy greens, nuts, seeds, and whole grains.