For severe constipation, the usual over-the-counter MiraLAX dose for adults and children 17 and older is 17 grams, or one capful, mixed into 4 to 8 ounces of a drink once daily. It should generally not be used for more than 7 days unless a doctor tells you to.

Some medical protocols mention higher or more frequent dosing, such as 17 grams twice daily for a short time, but this goes beyond the standard OTC instructions. Higher-dose “cleanout” approaches are usually meant to be done with medical guidance, especially if constipation is severe or not improving.

MiraLAX does not usually work immediately. The source material notes that it may take 1 to 4 days to produce a bowel movement. Side effects can include gas, nausea, cramping, and diarrhea, especially if too much is taken.

Do not keep increasing the dose on your own. Severe constipation, worsening belly pain, vomiting, bloating, fever, or inability to pass gas should be checked urgently. A primary care doctor or gastroenterologist can help decide whether MiraLAX is appropriate or whether another treatment is needed.