The standard adult dose of Miralax is 17 grams of powder, stirred into 4 to 8 ounces of any beverage, taken once a day. The bottle cap doubles as a measuring tool: fill it to the top of the white section, and you have exactly 17 grams. That’s really all there is to it, but a few details about mixing, timing, and what to expect will help you get the best results.
Measuring the Right Dose
Every Miralax bottle comes with a cap marked with a fill line at the top of the white section. That line corresponds to exactly 17 grams, which is the standard dose for adults and anyone 17 or older. You don’t need a kitchen scale or any special tools. If you buy the single-dose packets instead of the bottle, each packet contains the same 17 grams.
Some people need a slightly higher or lower dose depending on how their body responds. Doses can be adjusted up to a maximum of 34 grams (two capfuls) per day, but start with one capful and give it a few days before changing anything.
How to Mix It
Pour the measured powder into 4 to 8 ounces of any beverage: water, coffee, tea, juice, or a sports drink. The liquid can be cold, hot, or room temperature. Stir until the powder fully dissolves. Miralax is tasteless and odorless once dissolved, which makes it easy to mix into whatever you’re already drinking.
One important restriction: do not mix Miralax with starch-based thickeners, the kind sometimes used by people who have difficulty swallowing. The combination can cause problems with the thickener’s consistency.
When to Take It
There’s no required time of day. Most people pick a consistent time that’s easy to remember, like with breakfast or before bed. Consistency matters more than the specific hour because the effect builds over days rather than working immediately.
Miralax generally takes one to three days to produce a bowel movement. It works by drawing water into the colon, which softens stool and triggers more natural movement. This is a gradual process, not a sudden one, so don’t double up if nothing happens on day one.
How Long You Can Use It
The over-the-counter label recommends using Miralax for no more than 7 consecutive days without talking to a doctor. If constipation hasn’t improved after a week, that’s a sign something else may be going on or a different approach is needed. Some people do use Miralax for longer stretches under medical guidance, but that’s a decision to make with a provider, not on your own.
Getting Better Results
Miralax works by pulling water into your stool, so it needs water to work with. Drinking 6 to 8 glasses of water per day while taking it makes a noticeable difference. If you’re dehydrated, the powder has less to draw on and the effect will be weaker or slower. Pairing Miralax with adequate fiber intake (fruits, vegetables, whole grains) also helps keep things moving once the initial constipation resolves.
Miralax for Children
The over-the-counter packaging is labeled for ages 17 and up, but pediatricians frequently recommend Miralax for younger children at adjusted doses. Children’s doses are based on weight, not age, and vary significantly. A 22-pound toddler might get a very different amount than a 60-pound child. If your child’s doctor has recommended Miralax, follow their specific dosing instructions rather than the adult label. Children’s Hospital of Philadelphia, for example, publishes detailed weight-based dosing charts that pediatricians reference.
Who Should Not Take Miralax
Miralax is not safe for anyone with a bowel obstruction or intestinal blockage. Taking it in that situation can cause dangerous, potentially life-threatening side effects. People with eating disorders such as anorexia or bulimia should only use it under medical supervision.
You should also talk to a doctor before starting Miralax if you have ulcerative colitis, irritable bowel syndrome, kidney disease, or severe stomach pain with nausea or vomiting. A sudden change in bowel habits lasting two weeks or longer also warrants a conversation with a provider before reaching for a laxative. Miralax can interact with other medications, so mention it to your pharmacist if you take prescription drugs, supplements, or other over-the-counter products.
Storage
Keep the powder at room temperature, ideally between 68°F and 77°F. No refrigeration needed. Discard any unused powder after the expiration date printed on the container, and store it where children and pets can’t reach it.