What Milk of Magnesia Is Used For, and How Much Is Safe

Milk of Magnesia (magnesium hydroxide) is a well-known over-the-counter remedy. Understanding milk of magnesia uses and safe dosages can help you manage occasional constipation and indigestion effectively while minimizing risks.

What Is Milk of Magnesia?

Milk of Magnesia is a liquid suspension of magnesium hydroxide. It works in two main ways:

• As an osmotic laxative, it draws water into the intestines, softening stool and promoting bowel movements.
• As an antacid, it neutralizes excess stomach acid, relieving heartburn, acid indigestion, and sour stomach.

Milk of Magnesia Uses

Milk of magnesia uses extend beyond simple relief. Common applications include:

• Relieving occasional constipation in adults and children.
• Easing symptoms of acid indigestion, sour stomach, and heartburn.
• Serving as an antacid after heavy, spicy meals.
• Soothing minor skin irritations (e.g., mild sunburn or insect bites) when applied as a compress.

How Much Milk of Magnesia Is Safe?

Safe dosage depends on age and the condition being treated. These guidelines apply to the standard 400 mg/5 mL concentration (check your bottle’s label):

For Adults and Teenagers (12 years and older)

• Constipation: 30–60 mL (2–4 tablespoons) once daily at bedtime, or divide into smaller doses throughout the day.
• Acid indigestion/Heartburn: 5–15 mL (1–3 teaspoons) up to four times a day, 1–3 hours after meals and at bedtime.
• Maximum: Do not exceed 60 mL per day for constipation or 60 mL per day for antacid use.

For Children

• 6–11 years: 5–15 mL (1–3 teaspoons) once daily for constipation; 5 mL (1 teaspoon) up to four times a day for indigestion.
• 2–5 years: 2–5 mL (½–1 teaspoon) once daily for constipation; consult a doctor for antacid use.
• Under 2 years: Use only under direct medical supervision.

Always use the dosing device provided with the product. Do not use household spoons.

Tips for Safe Use

• Shake the bottle well before measuring.
• Take with a full glass of water to enhance the osmotic effect.
• Avoid taking other medications within 2 hours of milk of magnesia to prevent altered absorption.
• Limit use to no more than 7 consecutive days for constipation relief unless directed by a doctor.

Potential Side Effects and Warnings

While generally safe when used as directed, milk of magnesia can cause:

• Diarrhea or loose stools
• Stomach cramps or bloating
• Electrolyte imbalances (e.g., low potassium) with prolonged use
• Dehydration, especially in the elderly or those already dehydrated

Stop use and speak to a doctor if you experience:

• Severe abdominal pain or cramps
• Diarrhea lasting more than 24 hours
• Signs of dehydration: dry mouth, extreme thirst, reduced urination
• Muscle weakness or irregular heartbeat

Who Should Avoid Milk of Magnesia?

• People with severe kidney disease (magnesium is eliminated by the kidneys)
• Those with undiagnosed abdominal pain, nausea, or vomiting
• Individuals on magnesium-restricted diets or taking other magnesium-containing products

Interactions with Other Medications

Milk of magnesia can interfere with the absorption of:

• Antibiotics (e.g., tetracyclines, quinolones)
• Iron supplements
• Thyroid medications

To reduce interactions, take milk of magnesia at least 2 hours before or after other oral medications.

When to Seek Professional Help

Occasional constipation and heartburn are common, but persistent or severe symptoms may signal a more serious condition. Speak to a doctor if you have:

• Constipation lasting more than 7 days despite treatment
• Frequent or severe heartburn more than twice a week
• Blood in your stool or black, tarry stools
• Unexplained weight loss, fever, or persistent vomiting
• Difficulty swallowing or choking sensations

For non-urgent guidance, you might also consider a free, online symptom check, using the doctor approved Ubie Symptom Checker.

Key Takeaways

• Milk of magnesia uses include treating occasional constipation and neutralizing stomach acid.
• Adult doses for constipation: 30–60 mL once daily; for heartburn: 5–15 mL up to four times daily.
• Child dosing varies by age—always follow the label or your doctor’s advice.
• Limit use to 7 days for constipation; watch for diarrhea, cramps, and dehydration.
• Avoid if you have severe kidney disease or undiagnosed abdominal pain.
• Separate doses from other medications by at least 2 hours.
• Speak to a doctor about any serious or life-threatening symptoms.

Always read and follow the package directions. If you have questions or experience unusual symptoms, consult your healthcare provider.