How much magnesium should you take daily to help with constipation?

November 19, 2025 •

4 min read

According to the American Gastroenterological Association, magnesium oxide is an effective, low-cost first-line option for chronic idiopathic constipation. However, the optimal amount varies significantly depending on the form you choose and your individual needs. Deciding how much magnesium you should take daily to help with constipation requires careful consideration of different types and their potency.

Quick Summary

The daily magnesium amount for constipation depends on the supplement form, with magnesium citrate and oxide being common choices. Effective amounts differ, and side effects like diarrhea are possible. Always start with a low amount and adjust based on your body’s response under medical guidance.

Key Points

Amount Varies by Type: How much magnesium you take depends on the specific form, with common options for constipation being magnesium oxide, citrate, and hydroxide.
Start Low and Go Slow: To find your effective amount and avoid side effects like diarrhea, begin with a lower suggested amount and increase gradually under medical guidance.
Choose the Right Form: Magnesium oxide offers gentler, slower relief, while citrate acts faster and is more potent for acute constipation.
Always Hydrate: Drinking a full glass of water with each dose is essential for magnesium's osmotic action and for preventing dehydration.
Consult a Professional: Individuals with kidney disease, heart issues, or those on other medications should consult a doctor before taking magnesium, especially long-term.
Prioritize Diet First: Before relying on supplements, focus on increasing dietary fiber from foods and ensuring adequate hydration.

How Much Magnesium Should You Take Daily to Help With Constipation?

Understanding How Magnesium Relieves Constipation

Magnesium is an essential mineral that plays a crucial role in over 300 biochemical reactions in the body, including muscle and nerve function, blood pressure regulation, and bone health. For constipation relief, certain forms of magnesium work as an osmotic laxative. This means they draw water into the intestines from the body. This influx of water softens the stool and increases its bulk, which in turn stimulates intestinal muscle contractions (peristalsis) to promote a bowel movement.

Determining the Right Daily Amount

The correct daily amount of magnesium for constipation is not one-size-fits-all and depends largely on the specific form of magnesium you are taking and your body's tolerance. For occasional, short-term relief, higher amounts may be used under a doctor's supervision, while lower daily amounts are used for more consistent maintenance.

Magnesium Oxide: This is a common and inexpensive option for constipation, available in pill or powder form. Typical amounts can vary. Some studies have used varying amounts daily. Because it is poorly absorbed, more of the magnesium stays in the gut to exert its laxative effect. However, long-term use at higher amounts can increase the risk of elevated blood magnesium levels, especially for individuals with kidney issues.
Magnesium Citrate: This form is often sold as a liquid and is known for its higher bioavailability compared to magnesium oxide, though it still functions as an osmotic laxative for digestion. For adults and children over 12, typical amounts of the oral solution can be used within a 24-hour period. For constipation relief, it is often used as a potent, short-term solution and should not be used long-term without medical guidance.
Magnesium Hydroxide (Milk of Magnesia): As a liquid form of magnesium oxide, this is another popular osmotic laxative. For adults, typical amounts per day are used. It tends to act faster than the tablet form of magnesium oxide but can also cause more intense side effects like cramping.

Starting low and going slow is a crucial strategy when beginning any magnesium regimen for constipation to find your personal effective amount while minimizing potential side effects like diarrhea. Always take magnesium supplements with a full glass of water to enhance their osmotic effect and prevent dehydration.

Magnesium Form Comparison for Constipation


Feature	Magnesium Oxide	Magnesium Citrate	Magnesium Hydroxide	Magnesium Glycinate
Primary Use for Constipation	Standard, slower-acting laxative	Faster-acting, stronger osmotic laxative	Rapid-acting osmotic laxative	Not primarily a laxative; used for deficiency
Onset of Action	Typically takes over 6 hours; ideal for overnight relief	30 minutes to 6 hours	30 minutes to 6 hours	Not effective for this purpose
Primary Mechanism	Osmotic effect from poor absorption	Osmotic effect from good solubility	Osmotic effect from poor absorption	Highly absorbed; calming effect, not laxative
Best For	Consistent, daily use for chronic issues under medical guidance	Acute, occasional constipation relief or colon prep under medical guidance	Rapid but occasional relief, liquid preference	Correcting general magnesium deficiency
Risk of Side Effects	Lower risk of strong side effects due to slower action	Higher potential for diarrhea and cramps	Higher potential for diarrhea and cramping	Minimal laxative side effects

When to Consider Other Options and Precautions

While magnesium is a safe and effective option for many, it's not suitable for everyone. Individuals with impaired kidney function, myasthenia gravis, heart conditions, or other serious health issues should consult a doctor before starting magnesium supplements. Long-term, chronic use of magnesium laxatives should be managed under a healthcare provider's supervision, as prolonged dependence can occur. Natural dietary changes, including increasing fiber intake and water consumption, are always the first line of defense against constipation.

Conclusion

For those seeking to find out how much magnesium they should take daily to help with constipation, the answer is nuanced, depending on the supplement form. Magnesium oxide and citrate are the most common options, offering osmotic laxative effects to different degrees. For consistent, gentler relief, magnesium oxide is a popular choice, while magnesium citrate is often reserved for more acute episodes. Starting with a low amount and increasing gradually under medical guidance is key to finding the right balance for your body. However, before starting any new supplement regimen, especially for ongoing use, it is crucial to consult a healthcare professional to ensure safety and to discuss underlying causes of chronic constipation. For more guidance on digestive health, consult a reputable source like the National Institutes of Health.

Potential Complications and What to Watch For

Although magnesium is beneficial for many, be mindful of potential side effects, particularly if you are sensitive or taking higher amounts. Excessive intake can cause diarrhea, nausea, stomach cramps, and electrolyte imbalances. In rare, severe cases, especially in those with kidney disease, this can lead to hypermagnesemia, a serious condition with symptoms like low blood pressure, muscle weakness, and an irregular heartbeat. Always follow recommended guidelines from a healthcare professional and never exceed suggested daily amounts without medical advice. If you experience persistent side effects, stop taking the supplement and talk to a healthcare provider.

Other Considerations

When supplementing with magnesium, the timing can influence effectiveness. Many find taking it at night to be most convenient, allowing the osmotic effect to work overnight for a morning bowel movement. Consistency is also important for managing chronic constipation. Additionally, certain medications can interact with magnesium, so it's vital to discuss your supplement use with a pharmacist or doctor. Always prioritize dietary strategies first, including a high-fiber diet rich in vegetables, fruits, and whole grains, along with sufficient hydration.

Frequently Asked Questions

Magnesium citrate is often considered one of the best forms for constipation due to its high solubility and effective osmotic laxative properties. Magnesium oxide is another widely used and inexpensive option, though it is less bioavailable and works more slowly.

The time it takes for magnesium to work depends on the type. Faster-acting forms like magnesium citrate and magnesium hydroxide can produce a bowel movement within 30 minutes to 6 hours. Slower-acting forms, such as magnesium oxide, may take 6 hours or longer.

For most healthy individuals, occasional use of magnesium for constipation is safe. However, it is not recommended for long-term daily use without medical supervision, especially for chronic constipation. Daily, prolonged intake can lead to dependency or, in rare cases, dangerously high levels of magnesium in the blood, particularly if kidney function is impaired.

Yes, taking too much magnesium can cause side effects ranging from mild issues like diarrhea and cramping to more severe problems such as low blood pressure and irregular heartbeat. The Tolerable Upper Intake Level (UL) for supplemental magnesium is 350 mg for adults, though laxative amounts may exceed this under medical guidance.

Initial signs that magnesium is starting to work include abdominal cramping or gurgling, and an increased urgency to have a bowel movement. As the laxative effect progresses, you can expect to pass loose or watery stools.

While increasing dietary magnesium from sources like leafy greens, nuts, seeds, and whole grains is beneficial for overall health, it is often not enough to produce a significant laxative effect for constipation relief. Supplemental forms are typically needed for that purpose.

Magnesium glycinate is not the ideal choice for constipation relief. It is a highly absorbable form of magnesium, meaning most of it is taken into the bloodstream rather than staying in the gut to exert an osmotic effect. It is better suited for other uses, such as promoting relaxation and sleep.