Pediatric dosing of PEG 3350 is weight-based—about 0.4 g/kg/day for a 12-month-old, used only with a pediatrician guiding care.
Constipation around the first birthday is common, and many parents hear about polyethylene glycol 3350 (PEG 3350), sold as MiraLAX. This guide gives a clear, evidence-based way to size a dose for a 12-month-old, why the dose is based on body weight, how to mix it, and when to pause and call the doctor. It also explains label limits and why pediatric specialists still use PEG 3350 in babies under two under medical direction.
Quick Dose In Plain Numbers
Most pediatric teams start with 0.4 grams per kilogram of body weight each day for maintenance. For a 10-kg one-year-old, that works out to 4 grams daily. Adjust a little up or down to get soft, painless stools each day or every other day.
Why The Cap Matters
The MiraLAX bottle cap has a fill line that equals 17 grams. Since little kids need far less, thinking in fractions of a cap is handy. One quarter of a cap is about 4.25 grams; one eighth is about 2.1 grams. Always dissolve the powder in the full liquid amount and have your child drink the mix soon after.
Table 1: Weight To Dose Guide (0.4 g/kg/day)
This table shows typical one-year-old weights and the matching daily dose using the common starting point of 0.4 g/kg/day. The “cap fraction” column converts grams to part of a 17-g cap so measuring is easier.
| Weight (kg) | Daily Dose (g) | Cap Fraction (17 g = 1 cap) |
|---|---|---|
| 7 | 2.8 | ~0.16 cap (about 1/6) |
| 8 | 3.2 | ~0.19 cap |
| 9 | 3.6 | ~0.21 cap (about 1/5) |
| 10 | 4.0 | ~0.24 cap (just under 1/4) |
| 11 | 4.4 | ~0.26 cap (just over 1/4) |
| 12 | 4.8 | ~0.28 cap |
| 13 | 5.2 | ~0.31 cap (near 1/3) |
How Much Miralax For A 12-Month-Old? Dosage Explained
Because the product label is written for adults and teens 17 and up, dosing for infants sits in a gray zone. Specialists still use PEG 3350 for babies when diet changes and fluids are not enough. The weight-based method above comes from international pediatric guidelines. Start near 0.4 g/kg/day and fine-tune with your pediatrician based on stool pattern, gas, and bloating.
Miralax Dose For A 12-Month-Old: Safe Ranges And Signals
Maintenance range: 0.2 to 0.8 g/kg/day. Clean-out doses are higher and should be directed by a clinician. If your child is small for age, start on the low end. If stools stay hard after several days, step up slowly. Stop and call the doctor for blood in stool, belly swelling, fever, or vomiting.
How To Mix, Give, And Titrate
Mix the measured powder into 4 to 8 ounces of water, milk, or juice until it fully dissolves. Use the same drink each day so taste stays familiar. Give the dose at the same time daily for a steady effect. Track stools for a week: aim for soft, easy stools shaped like mashed potatoes. If stools are loose for two straight days, drop the dose by a small step. If stools are hard or painful, raise the dose by a small step.
Common Questions Parents Ask
How fast does it work? Many kids poop within 24 to 48 hours, sometimes a bit longer. Can I split the dose? Yes, twice-daily half-doses can help gassy kids. Can I stop once things improve? Keep going for weeks, then taper slowly with guidance from your pediatrician.
Safety Notes You Should Know
PEG 3350 stays in the gut and pulls water into the stool. That is why cramps are uncommon and why it pairs well with toilet-sitting and fiber. The over-the-counter label says to ask a doctor for anyone 16 or younger and not to use longer than seven days without medical advice. In practice, pediatric clinics often use it longer for chronic constipation and adjust the dose to effect.
When To Pause Or Avoid
Skip PEG 3350 and seek care right away for severe belly pain, green or bloody vomit, black stools, weight loss, or a newborn with a swollen belly. Children with kidney disease, bowel blockages, or swallowing trouble need a tailored plan. Breastfed babies who are under two months old need a different approach.
Alternatives And Add-Ons
Diet changes help, but they rarely fix hard stool alone in toddlers. Offer water through the day, serve fruits with skin, and add high-fiber sides like beans and oats. Lactulose can be an option for babies and tastes sweet. Short courses of stimulant laxatives sometimes enter the plan for clean-outs, led by a clinician. Toileting routines, small footstools, and calm potty time matter more than many parents expect.
Table 2: Dosing Context And Targets
This table sums up everyday use versus clean-out use, with goals for stool texture and timing. Maintenance is what most families need for a one-year-old.
| Scenario | Dose (g/kg/day) | Notes |
|---|---|---|
| Maintenance Start | ~0.4 | Adjust to one soft stool daily or every other day. |
| Maintenance Range | 0.2–0.8 | Go up or down in small steps based on stool texture. |
| Clean-Out (Clinic-Led) | 1.0–1.5 | For fecal impaction; medical direction required. |
| Mixing Volume | — | 4–8 oz liquid; dissolve fully before giving. |
| Target Stool | — | Soft, easy stools; no straining or pain. |
| Typical Course | — | Weeks to months, then slow taper if symptoms settle. |
Label Limits, Off-Label Use, And Why Teams Use It
The U.S. label for MiraLAX is written for adults and teens and tells buyers to measure 17 g with the cap and to ask a doctor for kids 16 or younger. Pediatric GI groups endorse PEG 3350 for children because trials and long experience show good results and a steady safety profile. That is why weight-based dosing appears in specialty guidelines even though the bottle does not include a child dose.
For label language and measuring details, see the FDA Drug Facts label. For pediatric dosing recommendations, see the joint guideline from NASPGHAN and ESPGHAN on functional constipation (starting dose 0.4 g/kg/day), available on NASPGHAN’s site.
Step-By-Step Titration Plan
Day 1–3: Start at 0.4 g/kg/day. Day 4–7: If stools are still hard, raise by 0.1–0.2 g/kg/day; if loose, drop by the same step. Week 2+: Hold the dose that gives one soft stool daily or every other day. Month 2+: If things stay easy, drop by 10–25% every few weeks. Return to the last dose that kept stools soft if trouble returns.
What This Looks Like In Real Life
A 12-month-old who weighs 9 kg might start at 3.6 g daily, which is about one fifth of a cap. Mixed in four ounces of water or milk, most kids drink it without fuss. If stools are still pebbly after three days, move to 4.5 g. If loose, drop to 3 g. Use a small kitchen scale or dose by measured cap fractions to stay consistent.
Answers To Searchers’ Exact Query
Two common searches are “how much miralax for a 12-month-old?” and “how much miralax for a 12-month-old?”. Both point to the same weight-based plan: start near 0.4 g/kg/day, then adjust to stool response with your pediatrician’s help.
Sources And Method In Brief
This guide follows the 2014 ESPGHAN/NASPGHAN guideline for functional constipation in infants and children (starting dose 0.4 g/kg/day; higher doses for fecal disimpaction), the FDA OTC Drug Facts for MiraLAX regarding product measuring and age limits, and pediatric clinic handouts that mirror the same ranges. Citations above link directly to the guideline PDF and the label page for quick checking.
Important Reminders For Caregivers
- Use grams or measured cap fractions; avoid guessing by spoons.
- Mix in enough liquid and have your child drink the full amount.
- Stay with the dose for several days before changing it, unless side effects appear.
- Call the doctor for red flags: blood in stool, fever, vomiting, belly swelling, poor weight gain, or severe pain.
- Pair dosing with water, fiber-rich foods, and calm toilet time.