MiraLAX Dosage by Weight Dosage Chart
MiraLAX (PEG 3350) is an OTC osmotic laxative commonly used for pediatric constipation. Unlike stimulant laxatives, it works by drawing water into the colon without causing cramping. Pediatricians use weight-based dosing for children because adult dose per body weight would be excessive. MiraLAX is also FDA-approved for adults.
MiraLAX Dosage by Weight Dosage by Age Group
| Age Group | Age Range | Dose Range | Notes |
|---|---|---|---|
| Children 11–18 kg (24–40 lb) | 11–18 kg | 8.5 g | ½ capful (approx); 1 capful = 17 g |
| Children 19–26 kg (42–57 lb) | 19–26 kg | 12.75 g | ¾ capful; mix in 8 oz liquid |
| Children 27+ kg (60+ lb) | 27+ kg | 17 g | Full capful (adult dose) |
| Adults (maintenance) | 18–64 years | 17 g | 1 capful once daily; up to 7 days OTC use |
| Adults (bowel prep) | 18–64 years | 238 g | Colonoscopy prep — physician supervised; dissolve in GoLYTELY/NuLYTELY |
Weight-Based Dosage Calculator
Enter your weight to calculate a personalized MiraLAX Dosage by Weight dose based on body weight. Standard pediatric dosing: 0.5 g per kg of body weight per day. Maximum 17 g/day. A 20 kg child = 10 g MiraLAX per day. Mix in 4–8 oz of juice, water, or non-carbonated beverage.
When and how to take MiraLAX Dosage by Weight
Can be given at any time of day. Many parents mix it with juice at breakfast for consistent daily use. Results typically occur within 12–72 hours of first dose. For chronic constipation, daily maintenance dosing is often needed for weeks.
Available Forms
PEG 3350 powder. Dissolves completely in any liquid. Tasteless and odorless.
1 capful = 17 g; cap provided with bottle
Same active ingredient as MiraLAX at lower cost.
Verify 17 g dose with included measuring device
Safety Cautions
- Children under 2 years: use ONLY under physician supervision.
- Do not use for more than 7 days OTC; longer use requires physician monitoring.
- Signs to seek emergency care: blood in stool, severe abdominal pain, persistent vomiting, or no bowel movement after 3 days.
- Ensure child remains hydrated — MiraLAX draws fluid into the colon from the body.
- Not intended for bowel prep without physician direction — bowel prep requires much higher doses.
- Mixing with carbonated beverages is not recommended (can cause foaming and imprecise dosing).
Frequently Asked Questions
How much MiraLAX for a child by weight?
The standard weight-based pediatric dose is 0.5–1 g of MiraLAX per kg of body weight per day, up to a maximum of 17 g (one capful). Example: a 20 kg (44 lb) child receives 10 g per day. Mix in 4–8 oz of juice or water. Always consult your child's pediatrician to confirm the dose and duration.
Is MiraLAX safe for children?
MiraLAX (PEG 3350) is widely used in pediatric practice for functional constipation. Pediatricians routinely recommend it for children over 2 years. The FDA has not formally approved MiraLAX for children under 17, but it is used off-label following NASPGHAN guidelines. Short-term use (under 7 days) at proper weight-based doses is considered safe.
How long does MiraLAX take to work?
MiraLAX typically produces a bowel movement within 12–72 hours of the first dose. It is not an immediate laxative. For chronic constipation, consistent daily dosing for several days is needed before the full effect is seen. If there is no bowel movement within 3 days, contact a physician.
Can adults take MiraLAX daily?
MiraLAX is FDA-approved for adults for up to 7 days OTC. Longer-term daily use (weeks to months) is practiced by some adults under physician supervision for chronic constipation, including IBS-C. Unlike stimulant laxatives, MiraLAX does not cause laxative dependence, but long-term self-medication without physician oversight is not recommended.
Sources & References
- NASPGHAN Clinical Practice Guidelines: Functional Constipation in Children
- FDA label: MiraLAX (PEG 3350)
- Pashankar DS & Bishop WP, J Pediatr 2001 — PEG 3350 for pediatric constipation