Metamucil (Psyllium) Powder Dosing for Constipation
For treating constipation, Metamucil (psyllium) powder should be taken at a standard dose of 5 grams twice daily with 8-10 ounces of fluid per dose. 1, 2
Dosing Recommendations
- The standard recommended dose is 5 grams of psyllium powder twice daily 1, 2
- Each dose must be taken with at least 8-10 ounces (240-300 mL) of water or other fluid 1
- Psyllium typically produces a bowel movement within 12 to 72 hours after administration 3
- For optimal results, treatment duration should be at least 4 weeks 4
- Higher doses (>10g/day) have shown better response rates in clinical trials 4
Administration Guidelines
- Mix the powder thoroughly in a full glass of water or other liquid until completely dissolved 5
- Drink immediately after mixing to prevent thickening 5
- Maintain adequate fluid intake throughout the day while using psyllium 1
- Take psyllium at consistent times each day for best results 5
Efficacy and Evidence
- Psyllium has been shown to increase spontaneous bowel movements per week compared to placebo (Mean Difference 2.32, CI 0.86–3.79) 1
- Clinical trials demonstrate that 75% of constipated patients respond to psyllium treatment 2
- Psyllium improves stool consistency and reduces straining during defecation 2
- Higher doses (>10g/day) and longer treatment durations (≥4 weeks) show greater improvement in stool frequency 4
Important Precautions
- CRITICAL SAFETY WARNING: Always take with adequate fluid (8-10 oz per dose) to prevent esophageal or intestinal obstruction 1, 6
- Psyllium works by absorbing water and expanding in the intestine - insufficient fluid intake can worsen constipation or cause blockage 6
- Psyllium may cause increased flatulence, especially during initial use 1, 2
- For mild constipation, psyllium can be used as first-line therapy before moving to stronger laxatives 1
- Psyllium can be used in combination with polyethylene glycol (PEG) for more severe constipation 1
Special Considerations
- Psyllium is considered both a soluble fiber and may have prebiotic potential 1
- Unlike wheat bran (insoluble fiber), psyllium (soluble fiber) is less likely to decrease stool water content or harden stool 1
- Psyllium is preferable to docusate (stool softener) which has not shown benefit in clinical trials 1
- Patients with very low fluid intake are more likely to be constipated and should focus on increasing overall fluid consumption 1
- Mixed fiber supplements containing both soluble and insoluble fiber may help reduce flatulence compared to psyllium alone 2