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Is Milk Of Magnesia Bad For You?

Also Known As: Magnesium hydroxide, Phillips' Milk of Magnesia



Short answer

Milk of Magnesia, containing magnesium hydroxide, is safe for short-term relief of constipation and indigestion as directed. However, overuse or long-term use can cause side effects like electrolyte imbalance, dependency, and gastrointestinal issues, and can interfere with medication efficacy and nutrient absorption. It poses significant risks for those with kidney disease. Balanced use is key.



Long answer

Active Ingredients and Primary Uses of Milk of Magnesia

The main active ingredient in Milk of Magnesia is magnesium hydroxide. This compound is a naturally occurring mineral that has several essential roles in the body, including nerve transmission, muscle contraction, and bone formation. In Milk of Magnesia, however, its primary use is as an antacid and laxative. Let's delve into both of these aspects:

Antacid Properties:

Magnesium hydroxide operates as an antacid by neutralizing stomach acid. This results in increasing the pH level of the stomach contents, offering relief from symptoms caused by excess stomach acid. Conditions such as heartburn, gastric reflux, and indigestion are commonly addressed with the antacid properties of Milk of Magnesia.

  • Neutralizes excess stomach acid
  • Relieves symptoms like heartburn and indigestion
  • Increases stomach pH

Laxative Effects:

As a laxative, magnesium hydroxide draws water into the intestines, a process known as osmosis. This increased water helps to soften stools and promote intestinal motility, thereby relieving constipation. Unlike some other laxatives that stimulate the bowel, Milk of Magnesia works more gently, making it a preferred choice for individuals who need to avoid straining, such as those with hemorrhoids.

  • Draws water into the intestines
  • Softens stool for easier passage
  • Gentle on the bowel

While the efficacy of Milk of Magnesia for these uses is well-documented, it's vital to consider the pharmacokinetics—that is, how the compound behaves in your body. Oral administration leads to minimal absorption of magnesium hydroxide into systemic circulation; it primarily acts locally in the digestive system. This low level of absorption significantly reduces the potential for systemic side effects, which is beneficial for the consumer. Yet, this doesn't rule out the possibility of side effects entirely, particularly with excessive or prolonged use.

Research indicates that proper use of magnesium hydroxide, following dosage guidelines, is generally safe for short-term relief of digestive complaints. Clinical studies, such as those reported by the National Institutes of Health (NIH), have often supported its use, but also underline the need to consider individual health conditions and potential drug interactions.

It's imperative to consult healthcare providers before initiating treatment with Milk of Magnesia, especially for individuals with kidney disease, those on certain medications, or anyone with a health condition that could be affected by alterations in mineral levels.

Short-term Relief vs. Long-term Side Effects

Milk of Magnesia, primarily composed of magnesium hydroxide, is a common over-the-counter remedy for occasional constipation and acid indigestion. When determining its impact on your health, it's essential to distinguish between its short-term relief benefits and potential long-term side effects.

Short-term Benefits:

  • Laxative Effect: Milk of Magnesia acts quickly to relieve constipation, usually producing a bowel movement within 30 minutes to 6 hours. It does so by drawing water into the intestines, which helps soften stool and encourages bowel activity.
  • Antacid Properties: Its ability to neutralize stomach acid can provide prompt relief from heartburn, sour stomach, or acid indigestion.

Short-term Side Effects:

  • Gastrointestinal Effects: While effective, it can lead to side effects such as diarrhea, abdominal cramping, and an electrolyte imbalance with overuse, even in the short term.
  • Drug Interactions: Magnesium hydroxide can interact with other medications, possibly reducing their efficacy if taken concurrently.

Long-term Side Effects:

  • Hypermagnesemia: Excessive use can lead to hypermagnesemia, a condition characterized by elevated magnesium levels in the blood.
  • Dependency: Chronic use for constipation relief can result in bowel dependency, meaning the bowel's natural motility is reduced, and long-term laxative use becomes necessary to produce bowel movements.
  • Renal Concerns: Patients with kidney issues may experience worsening renal function due to the accumulation of magnesium, which kidneys normally filter out.
  • Electrolyte Imbalance: Long-term use may lead to imbalances in potassium, sodium, and calcium levels, each pivotal for various bodily functions.

To better understand long-term side effects, let’s delve into research and expert opinions:

  • A study published in the World Journal of Gastroenterology indicated that prolonged use of magnesium-based laxatives can lead to serious electrolyte disturbances and complications 1.
  • According to the National Kidney Foundation, individuals with kidney disease should avoid using magnesium hydroxide due to the increased risk of accumulating high levels of magnesium in the blood 2.

Ultimately, for short-term usage, Milk of Magnesia can provide significant relief from specific digestive issues when used as directed. However, it is not designed for long-term use, and doing so can lead to severe health consequences. Patients should always consult their healthcare provider prior to initiating any long-term treatment with over-the-counter medications, including Milk of Magnesia.


  1. World Journal of Gastroenterology: "Chronic use of laxatives: prevalence, efficacy, and safety data".
  2. National Kidney Foundation: "Over-the-counter medications and chronic kidney disease".

Electrolyte Imbalance and Kidney Function Concerns

Milk of Magnesia, known chemically as magnesium hydroxide, is an over-the-counter medication commonly used as an antacid and laxative. While it offers effective relief for indigestion and constipation, concerns about its impact on electrolyte balance and kidney function should not be overlooked, particularly with excessive or prolonged use.

Impact on Electrolyte Balance:

Magnesium, the active ingredient in Milk of Magnesia, is one of several critical electrolytes required for the normal functioning of cells and organs. Electrolytes are minerals that carry an electric charge and are essential for processes such as nerve signaling and muscle contraction. They must remain in proper balance to maintain health.

  • Hypermagnesemia: Excessive intake of magnesium can lead to hypermagnesemia, a condition characterized by an abnormally high level of magnesium in the blood. Symptoms can range from nausea and vomiting to more severe effects like lowered blood pressure, muscle weakness, and heart rhythm abnormalities.
  • Interference with Other Electrolytes: High levels of magnesium from Milk of Magnesia can interfere with the balance of other electrolytes, such as calcium and potassium, potentially leading to additional health issues.

Considerations for Kidney Function:

Kidneys play a pivotal role in regulating electrolyte levels, including magnesium. When functioning normally, the kidneys filter and excrete excess magnesium to maintain balance. However, individuals with compromised kidney function may not be able to excrete magnesium effectively, leading to an accumulation in the body.

  • Risks for Individuals with Kidney Disease: For those with chronic kidney disease or decreased renal function, taking Milk of Magnesia could pose significant risks. These individuals should avoid using the product or do so only under strict medical supervision.
  • Medication Interactions: Milk of Magnesia can interact with certain medications, such as diuretics and antibiotics, which can further impact kidney function and electrolyte levels.

It is vital to monitor the dosage and frequency of Milk of Magnesia use to prevent possible complications related to electrolyte imbalance and kidney function. Individuals with pre-existing health conditions or those taking other medications should consult healthcare professionals before using Milk of Magnesia.

Extensive research into the effects of magnesium on electrolyte balance and kidney function reinforces the need for caution. A study published in Advances in Chronic Kidney Disease highlights the risks of magnesium-based laxatives in patients with renal impairment, supporting the notion that such populations should avoid products like Milk of Magnesia or use them only with medical guidance.

In conclusion, while Milk of Magnesia can be safe for temporary use in individuals with healthy kidney function, awareness of the potential risks regarding electrolyte balance and kidney health is crucial for preventing adverse health outcomes.

Risks Associated with Overuse or Misuse of Laxatives

Laxatives are substances that help stimulate bowel movements or soften the stool to aid in its passage. Milk of Magnesia is a type of saline laxative known for its fast-acting relief of constipation. However, like any medication, it must be used correctly to avoid potential health risks. Overuse or misuse of laxatives can lead to several health issues that can range from uncomfortable to severe. Understanding these risks is crucial for safe and effective use.

1. Electrolyte Imbalance: Overusing Milk of Magnesia can result in an imbalance of electrolytes—vital minerals in your body such as sodium, potassium, and magnesium. Electrolyte imbalance can lead to muscle weakness, spasms, irregular heartbeat, and in extreme cases, seizures.

Expert Opinion: The World Gastroenterology Organisation suggests that long-term or excessive use of laxatives can lead to hypokalemia (low potassium levels) and other significant electrolyte disturbances.

2. Dehydration: Excessive use of saline laxatives like Milk of Magnesia can cause dehydration due to increased stool output. Dehydration, if not corrected, can contribute to kidney injury, and affect cardiovascular and neurological functions.

3. Dependency: Habitual reliance on laxatives for bowel movements can lead to laxative dependency. Over time, the bowels can become less responsive to natural stimuli, and larger doses of laxatives may be needed to produce the same effect—a condition known as the "laxative effect."

Expert Opinion: According to the American Gastroenterological Association, chronic use of stimulant laxatives may lead to dependency and a decreased ability of the colon to contract on its own.

4. Gastrointestinal Issues: The misuse of Milk of Magnesia can contribute to gastrointestinal disturbances, such as increased gas, bloating, and cramping. An overused bowel can also become worn out, leading to conditions such as lazy bowel syndrome, where the colon's haustral folds become effaced, making it difficult to pass stool without the use of laxatives.

5. Risk of Toxicity: Very high doses of Milk of Magnesia can lead to magnesium toxicity, particularly in individuals with kidney dysfunction, as the kidneys are responsible for filtering out excess magnesium. Signs of magnesium toxicity include nausea, low blood pressure, slowed heart rate, and respiratory distress.

Research Insight: A study published in the Journal of Medical Toxicology highlights that hypermagnesemia (high magnesium level in the blood) can occur after excessive intake of magnesium-containing laxatives, especially in individuals with impaired renal function.

6. Impact on Nutrient Absorption: Prolonged laxative use can affect the body’s ability to absorb nutrients from the digestive tract, potentially leading to malnutrition or deficiencies in vitamins and minerals. This is due to the shortened transit time in the intestine, not allowing sufficient nutrient uptake.

In conclusion, while Milk of Magnesia can be highly beneficial for treating occasional constipation, it is imperative to adhere to recommended doses and durations of use. If constipation persists, it is advisable to consult a healthcare provider to avoid the serious risks associated with the overuse or misuse of laxatives.

Interactions with Medications and Nutrient Absorption

Magnesium hydroxide, the active ingredient in Milk of Magnesia, is generally safe when used as directed. However, it can interact with several types of medications, affecting their absorption and efficacy. Understanding these interactions is crucial for ensuring that both the medication and Milk of Magnesia work effectively and safely.

Interactions with Specific Medications

Certain drugs have known interactions with magnesium hydroxide that can either reduce their effectiveness or result in adverse effects. Here's a list of medication categories that can interact with Milk of Magnesia:

  • Antibiotics: Tetracyclines and quinolones can bind to magnesium, preventing their proper absorption. Therefore, taking these antibiotics within two hours of Milk of Magnesia could reduce their effectiveness.
  • Iron supplements: Milk of Magnesia may decrease the absorption of iron, potentially leading to reduced efficacy of iron supplements.
  • Bisphosphonates: Used to treat osteoporosis, these medications' effectiveness can be hindered when taken too close to a dose of Milk of Magnesia.
  • Medications for Hypertension: Magnesium has hypotensive effects that could potentially enhance the effects of antihypertensive drugs.
  • Other Laxatives or Antacids: Combining multiple laxatives or antacids can lead to an electrolyte imbalance or additive adverse effects.

Impact on Nutrient Absorption

Magnesium hydroxide acts as an osmotic laxative, which means it draws water into the intestines. This increase in water can speed up bowel transit time, potentially reducing the time your body has to absorb nutrients from food. Regular use of Milk of Magnesia may lead to:

  • Reduced absorption of fats, proteins, and carbohydrates, which could negatively affect energy levels and nutritional status.
  • Alterations in the absorption of fat-soluble vitamins (Vitamins A, D, E, and K), which could potentially lead to deficiencies over time.
  • Decreased absorption of other minerals like potassium, sodium, and calcium, which could contribute to an electrolyte imbalance with prolonged use.

It's always recommended to discuss with a healthcare professional before combining any over-the-counter product like Milk of Magnesia with prescription medications. Furthermore, it is also important to understand the dietary implications if you are using Milk of Magnesia regularly.

Timing of Doses

To minimize interactions with medications and nutrient absorption issues, it's often advised to space the ingestion of Milk of Magnesia and other medications or supplements. A common recommendation is to take other medications at least 2 hours before or 4 hours after Milk of Magnesia. Nonetheless, consultation with a healthcare provider can provide personalized guidance based on specific medications and individual health needs.

Monitoring and Management

For individuals required to use Milk of Magnesia over an extended period, medical supervision is important to monitor for signs of nutrient deficiencies or medication interactions. Regular blood tests may be necessary to assess the levels of minerals and ensure that any supplementation or dietary modifications are appropriately adjusted.

Overall, while Milk of Magnesia can be an effective short-term solution for constipation, it is essential to be aware of its interactions with other medications and its potential to affect nutrient absorption. Responsible use, under medical supervision, ensures that these risks are minimized.

Frequently asked questions

Yes, certain lifestyle changes can help alleviate constipation and reduce the need for laxatives. Incorporating a diet high in fiber, drinking plenty of fluids, engaging in regular physical activity, and establishing a consistent bowel routine can significantly improve bowel health and decrease the reliance on products like Milk of Magnesia.

Milk of Magnesia is primarily used to treat constipation and symptoms of indigestion like heartburn and acid reflux. Although it may sometimes be used off-label for other purposes, it is important to consult a healthcare provider for advice on alternative uses to ensure safety and efficacy.

Milk of Magnesia is considered gentler than stimulant laxatives, as it works by drawing water into the intestines to soften stool rather than directly stimulating bowel movements. This can make it safer and have fewer side effects like abdominal cramps when used according to guidelines. Stimulant laxatives, on the other hand, may lead to more severe discomfort and a greater risk of dependency with long-term use.

Milk of Magnesia may be used with caution in children and during pregnancy, but it is crucial to consult a pediatrician or obstetrician before use. Dosage and frequency may need to be adjusted, and the healthcare provider can assess whether Milk of Magnesia is the most appropriate treatment option.

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Possible short-term side effects

  • diarrhea
  • abdominal cramping
  • electrolyte imbalance
  • reduced medication efficacy

Possible long-term side effects

  • hypermagnesemia
  • bowel dependency
  • worsened renal function
  • electrolyte imbalance
  • nutrient deficiencies
  • potential for medication interactions

Ingredients to be aware of

  • magnesium hydroxide


  • relieves constipation
  • neutralizes stomach acid
  • gentle on bowel
  • quick laxative effect
  • softens stool
  • increases stomach ph

Thank you for your feedback!

Written by Dr. Becky Maes
Published on: 03-15-2024

Thank you for your feedback!

Written by Dr. Becky Maes
Published on: 03-15-2024

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