Preparing Miralax is straightforward: stir one capful of powder into 4 to 8 ounces of any beverage until it dissolves. The powder is tasteless and odorless, so it blends into most drinks without changing the flavor. But the details matter depending on whether you’re using it for everyday constipation or prepping for a colonoscopy, since those two situations call for very different amounts.
Mixing Miralax for Daily Use
For regular constipation relief, measure one capful of powder (17 grams, marked on the cap) and add it to 4 to 8 ounces of liquid. Stir until the powder fully dissolves. You can use cold, hot, or room temperature beverages. Water, juice, soda, coffee, and tea all work. The powder should not be combined with starch-based thickeners sometimes used by people with swallowing difficulties.
A few practical tips make the process smoother. The powder dissolves faster in warm liquids than cold ones, so if you notice grittiness, try stirring it into something warm or giving it an extra 30 seconds of stirring. Many people mix it into their morning coffee or juice so it becomes part of their routine. The amount of liquid you choose within that 4 to 8 ounce range doesn’t change how well it works. It’s purely a matter of preference.
How Miralax Works in Your Body
Miralax is an osmotic laxative, which means it draws water into the stool as it moves through your colon. Unlike stimulant laxatives that force your intestinal muscles to contract, Miralax simply makes the stool softer and easier to pass by keeping more water with it. This gentler approach is why it generally takes one to three days to produce a bowel movement rather than working within hours. Take it once a day, and expect results within that window rather than immediately after your first dose.
How Long You Can Use It
The standard over-the-counter recommendation is to use Miralax for up to seven consecutive days. If constipation hasn’t improved after a week of daily use, that’s the point to talk with a healthcare provider rather than continuing on your own. Some people are prescribed Miralax for longer-term use under medical guidance, but the seven-day limit applies when you’re self-treating.
Preparing Miralax for a Colonoscopy
Colonoscopy prep uses a much larger dose of Miralax mixed into a sports drink, and the goal is to completely clear your bowels before the procedure. This is a different process from daily use, so follow the specific instructions your doctor’s office provides. Here’s what a typical prep looks like.
What You’ll Need
- 64 ounces of a clear sports drink like Gatorade, Propel, or Crystal Light. Avoid red, orange, or purple colors, since these can stain the colon lining and interfere with the exam. If you have diabetes, sugar-free versions like Gatorade G2 are a better choice.
- One 8.3-ounce bottle of Miralax (238 grams). This is a full bottle, not the single capful used for constipation.
- Four bisacodyl laxative tablets (5 mg each). Make sure you’re buying the stimulant laxative version, not the stool softener, as they’re often sold under the same brand name.
None of these require a prescription.
Mixing the Solution
The day before your colonoscopy, pour the entire 8.3-ounce bottle of Miralax into a pitcher with all 64 ounces of the sports drink. Stir until the powder is completely dissolved. You can refrigerate the mixture if you prefer it cold, which many people find makes it easier to drink in large quantities.
The Drinking Schedule
Colonoscopy prep is split into two rounds. The evening before your procedure, take the four bisacodyl tablets at 5:00 p.m. At 6:00 p.m., start drinking the first half of the solution: 32 ounces total, broken into 8-ounce glasses every 15 minutes. That’s four glasses over the course of an hour.
The second round happens six hours before your scheduled colonoscopy time. You’ll drink the remaining 32 ounces on the same schedule: one 8-ounce glass every 15 minutes. This split-dose approach is more effective at clearing the colon than drinking everything in one sitting, and it tends to be easier on your stomach.
Expect frequent, watery bowel movements to start within one to two hours of your first glass. By the time you finish the second round, your stool should be clear or light yellow, which signals that your bowels are clean enough for the procedure. Stay close to a bathroom during the entire prep process.
Making Large-Volume Prep Easier to Drink
Drinking 64 ounces of prep solution is the part most people dread. Keeping the mixture cold helps considerably, since the flavor is less noticeable at lower temperatures. Sucking on a lemon wedge or hard candy between glasses can cut through the sweetness. Using a straw also reduces how much you taste. If you feel nauseous during the process, slow down for 15 to 20 minutes before resuming. The goal is to finish each 32-ounce round, even if you need a brief pause.