weightlossprotips

Editorial roundup · Updated 2026

Best Fiber Supplements for GLP-1 Constipation

One in three GLP-1 patients experiences constipation. The fix is usually a soluble fiber taken daily. Here are the three we recommend to start with.

How we picked

We looked for evidence-backed active ingredients (psyllium, PHGG), clear per-serving dosing, and tolerability during the sensitive first few weeks on a GLP-1.

  1. #1 Editor's pick
    4-in-1 Psyllium Fiber — Metamucil

    Metamucil

    4-in-1 Psyllium Fiber

    The gold-standard soluble fiber — 3 g psyllium per dose

    4.7

    $0.30 / serving

    • Decades of clinical data — the most-studied fiber supplement
    • Slows gastric emptying → smooths post-meal glucose
    • Available at every drug store
    • Texture takes getting used to (thickens fast)
    Read full reviewVisit
  2. #2 Top rated
    PHGG Prebiotic Fiber — Regular Girl

    Regular Girl

    PHGG Prebiotic Fiber

    Tasteless, dissolvable prebiotic + probiotic — mixes into anything

    4.5

    $1.15 / serving

    • Zero taste, zero texture — mixes into coffee, water, protein shakes
    • PHGG is the gentlest soluble fiber (won't cause bloating)
    • Adds beneficial probiotic strains too
    • More expensive per gram than psyllium
    Read full reviewVisit
  3. #3 Top rated
    Calm Magnesium Citrate — Natural Vitality

    Natural Vitality

    Calm Magnesium Citrate

    The best-selling magnesium powder — 325 mg per scoop

    4.6

    $0.60 / serving

    • Two-purpose: fixes constipation AND improves sleep
    • Citrate form has the best bioavailability + laxative action
    • Pleasant citrus flavor — easier than horse-pill magnesium tablets
    • Too high a dose = loose stools (start with half a scoop)
    Read full reviewVisit

Other fiber roundups

Best Magnesium for Constipation & Sleep

See ranking