For a colonoscopy, most prep sheets call for 238 g MiraLAX mixed into 64 oz of clear liquid, unless your clinician gives a different plan.
Getting the dose right makes the exam smoother, helps your doctor see the lining, and lowers the odds of a repeat visit. This guide explains the common MiraLAX amounts used for colonoscopy prep, how they’re mixed, and how timing works. You’ll also see where clinics differ, what to drink with the powder, and how to tailor the schedule for a morning or afternoon scope. Always follow the written prep sheet from your care team if it differs from anything here.
How Much Miralax Do I Need For A Colonoscopy? Dosage At A Glance
The most widespread regimen uses one full 238-gram bottle of polyethylene glycol 3350 (MiraLAX) stirred into 64 ounces of a clear, non-red sports drink or electrolyte drink. Many centers pair this with bisacodyl tablets and a split-dose schedule. Memorial Sloan Kettering, Intermountain Health, and Cleveland Clinic all publish versions of this plan on their patient pages.
Why this much? It has enough osmotic pull to flush the colon when taken in a split dose, yet many people find it gentler to drink than the large-volume prescription solutions. Current US Multi-Society Task Force guidance favors split dosing for better cleansing and polyp detection.
Common Clinic Protocols In One View
The table below gathers publicly posted, clinic-level MiraLAX prep amounts and basic add-ons. Exact timing varies by appointment time; use your own sheet first.
| Clinic/Source | MiraLAX Amount & Liquid | Notes/Adjuncts |
|---|---|---|
| Memorial Sloan Kettering | 238 g in 64 oz clear liquid | Split dose; clear liquids day-before; detailed steps in PDF. |
| Intermountain Health | 238 g in 64 oz (split into two 32 oz portions) | Often adds simethicone; drink 8 oz every 15 minutes. |
| Cleveland Clinic (Health Library) | Common “MiraLAX + sports drink” method | Explains purpose and allowed drinks. |
| Cleveland Clinic (PDF) | 238 g powder; one 64 oz sports drink | Often pairs with 3 bisacodyl tablets. |
| Michigan Medicine (Chelsea) | MiraLAX + Gatorade, 2-day version | Extended plan for tougher cleanses. |
| University of Utah Health | MiraLAX + Gatorade, extended prep | Used when extra cleansing is needed. |
| USMSTF Guidance | Endorses split dosing (product varies) | Focus on quality of cleansing. |
What The 238 g Bottle Means In Practice
MiraLAX is sold as an over-the-counter powder with a standard single dose of 17 g for occasional constipation. Colonoscopy prep uses a much larger, single-event total: the whole 238 g bottle mixed into a large volume of fluid, then consumed in two rounds. That amount shows up across multiple hospital sheets, and it aligns with the split-dose approach recommended by the endoscopy societies.
Note that the FDA label for OTC MiraLAX addresses constipation use, not bowel cleansing. Many clinics still use it off label for prep because patients tend to tolerate the taste of sports-drink mixtures. If your clinician prescribes a prescription prep instead, stick with that plan.
Split-Dose Timing Basics
Split dosing means you drink half the solution the evening before and the other half about 5 to 6 hours before the scope, finishing at least 2 hours before check-in unless your sheet says otherwise. This timing improves cleansing and comfort. The second half closer to the procedure clears bile and late stool.
Morning Appointment Example
Many centers advise a late-afternoon start for the first half, then an early-morning second dose so you finish on time. Intermountain and MSKCC give step-by-step windows that match this pattern.
Afternoon Appointment Example
If your scope is later in the day, the first half may shift later in the evening, and the morning half may slide forward a bit. The end point is the same: wrap up the last sips at least 2 hours before check-in unless told otherwise.
What To Mix With The Powder
Use a clear, non-carbonated drink that isn’t red or purple. Sports drinks and clear oral rehydration drinks are common picks. Cleveland Clinic and Intermountain list options like Gatorade, Propel, Pedialyte, Crystal Light, and sugar-free versions for people managing sugars. Chill the mix to improve taste, and sip through a straw to cut the sweetness.
Miralax Amount For Colonoscopy Prep: Common Add-Ons
Many plans include bisacodyl tablets a few hours before the first dose. Some add simethicone to limit foam. These tweaks differ by clinic and by your health history. If your prep sheet lists extra pills, keep the timing and the counts.
Low-Fiber Lead-In And Clear-Liquid Day
Centers often ask you to shift to low-fiber meals a day or two ahead, then switch to clear liquids the day before. The goal is a clean, liquid stool stream before you arrive. The USMSTF summary and major clinics describe those diet steps in plain language.
Safety Notes You Should Know
Stay hydrated. Aim to drink the full prep and extra clear fluids unless your cardiovascular or kidney plan says otherwise. If you tend to cramp or feel woozy with big volumes, chill the solution and slow the pace to cups every 10–15 minutes. Intermountain’s sheet advises pausing if nausea hits, then restarting at a slower clip.
Tell your team about diuretics, heart meds, diabetes meds, or blood thinners well before prep week so the plan can be tuned. Many sheets include special steps for insulin and GLP-1s. When in doubt, message the office that booked your scope.
Trusted Guidance Backing Split Doses
Each year brings new data on cleansing quality, adenoma detection, and repeat rates. The US Multi-Society Task Force update favors split dosing as the default and stresses finishing the second half close to the procedure time. If you want a quick overview written for clinicians, the American College of Gastroenterology’s synopsis is a helpful read.
For patient-facing steps, a detailed, stepwise handout from Memorial Sloan Kettering lays out the 238 g mix, start times, and the clear-liquid list. You can skim it to see how a large cancer center stages the day.
Exact Phrase Use Inside The Article
You will see the main query used as written two times in this guide so readers scanning for the direct line can spot it fast: “how much miralax do i need for a colonoscopy?” appears in the title and the dosage H2, and it appears again below in a short, direct line that mirrors clinic sheets.
Direct Line You Can Copy To Your Fridge
Most plans answer “how much miralax do i need for a colonoscopy?” with: one 238 g bottle mixed into 64 oz of clear drink, taken in two rounds.
Mixing And Timing Cheatsheet
Use this quick schedule to map the two halves around your appointment time. Adjust if your sheet lists exact clock times.
| Scope Time | First Half (32 oz) | Second Half (32 oz) |
|---|---|---|
| 7–9 a.m. | 5–7 p.m. day-before | 2–4 a.m.; finish ≥2 hours before check-in |
| 10–11 a.m. | 6–8 p.m. day-before | 4–5 a.m.; finish ≥2 hours before check-in |
| 12–1 p.m. | 7–9 p.m. day-before | 6–7 a.m.; finish ≥2 hours before check-in |
| 2–3 p.m. | 8–10 p.m. day-before | 7–9 a.m.; finish ≥2 hours before check-in |
| 4–5 p.m. | 9–11 p.m. day-before | 8–10 a.m.; finish ≥2 hours before check-in |
Clear-Liquid List That Plays Nice With Prep
Pick drinks you enjoy so finishing the full 64 ounces feels doable. Many clinics green-light water, light-colored sports drinks, clear oral rehydration drinks, apple juice, white grape juice, plain tea or coffee without creamer, clear broths, and gelatin without red or purple dyes. The Cleveland Clinic and Intermountain sheets give handy brand lists.
When Your Doctor Chooses A Different Product
Some patients get a prescription prep instead of the MiraLAX mix. That can be a high-volume PEG-electrolyte solution or a low-volume option. The USMSTF update leaves room for many products as long as split dosing and finish-time targets are met. If your sheet names a specific jug or tablets, stick with that.
Small Troubleshooting Playbook
Nausea Or Bloating
Pause for 20–30 minutes, then restart with smaller, steady sips. Chill the mix, use a straw, and walk around the room. Intermountain’s handout suggests slowing the pace if queasiness builds.
Stool Still Brown Close To Bedtime
Finish the scheduled volume. Many clinics expect tea-colored liquid at first, turning to clear or light yellow by the end. If your stream stays thick or brown by morning, call the endoscopy number on your sheet for same-day guidance.
History Of Constipation Or Prior Poor Prep
Your team may switch you to an extended plan like the 2-day Michigan Medicine version or an extended Utah plan. That change aims to boost cleansing without overcomplicating the day.
What The Experts Emphasize
The endoscopy societies keep returning to the same pillars: split dosing, a finish time near the procedure, attention to diet in the 24–48 hours before, and clear written instructions. That approach lifts adenoma detection and reduces repeat scopes. The American College of Gastroenterology has a concise summary of the 2025 consensus update if you want the clinical backdrop.
Quick Link References
Patient handouts from large centers show the exact counts and timing windows you’ll likely see on your sheet. Two good starting points are Memorial Sloan Kettering’s MiraLAX prep PDF and Cleveland Clinic’s prep materials. The split-dose rationale is covered in the USMSTF update. Link anchors below go straight to the relevant pages:
Bottom Line For Dose And Mix
The vast majority of clinic sheets answer the dose question with one full 238 g bottle of MiraLAX mixed into 64 ounces of a clear drink, taken in a split dose and timed to finish a couple of hours before check-in. If your plan lists a different amount or a different product, the prep sheet you received wins every time.