From the FDA Drug Label
Directions • shake well before use • do not exceed the maximum recommended daily dose in a 24 hour period • dose may be taken once a day preferably at bedtime, in divided doses or as directed by a doctor • drink a full glass (8oz) of liquid with each dose agedose Adults and children over 12 years of ageTake 30mL (one unit dose) to 60mL (2 unit dose)
The recommended dose and frequency of magnesium hydroxide (Milk of Magnesia) for treating constipation is:
- 30mL to 60mL per day for adults and children over 12 years of age, taken once a day (preferably at bedtime) or in divided doses as directed by a doctor 1.
- For children under 12 years of age, the dose should be determined by a doctor 1.
From the Research
For constipation, the recommended dose and frequency of magnesium hydroxide (Milk of Magnesia) is 30-60 mL of the regular liquid formulation or 15-30 mL of the concentrated liquid, taken once daily preferably at bedtime, as it is equally effective and safe as polyethylene glycol 3350 for treating functional constipation in children from six months to eighteen years of age 2. The dose for children aged 6-11 years is 15-30 mL of regular liquid once daily, while children 2-5 years should take 5-15 mL daily. Some key points to consider when using milk of magnesia for constipation include:
- It typically produces a bowel movement within 30 minutes to 6 hours
- It should not be used for more than 7 consecutive days without medical supervision
- It should be taken with a full glass of water to prevent dehydration
- It works as an osmotic laxative by drawing water into the intestines, which softens stool and stimulates bowel movements
- Side effects may include abdominal cramping, nausea, or diarrhea
- Those with kidney disease should consult a healthcare provider before using this medication as magnesium can accumulate in the body
- If constipation persists beyond a week of treatment, or if you experience severe abdominal pain, nausea, or vomiting, seek medical attention. A recent study found that reducing the number of daily doses of magnesium oxide does not affect its laxative action 3, but this may not be directly applicable to magnesium hydroxide. Another study compared the efficacy and safety of osmotic and stimulant laxatives for the management of childhood constipation, and found that polyethylene glycol preparations may be superior to placebo, lactulose, and milk of magnesia 4. However, the most recent and highest quality study found that magnesium hydroxide is equally effective and safe as polyethylene glycol 3350 for treating functional constipation in children from six months to eighteen years of age 2.