Can I prevent it instead of treating it?

Largely yes. Start the hydration and soluble fibre routine the week BEFORE you start the GLP-1, not after constipation hits. Most people who do this either avoid significant constipation entirely or find it mild.

Will the constipation go away on its own?

Often yes, partially, after 4-6 weeks at each dose level as the gut adjusts. But it tends to come back at each dose escalation. Building the routine in step 1-3 above means you don't have to relearn it each escalation.

Is the constipation worse on Mounjaro than Ozempic?

Slightly. SURMOUNT-1 reported 12-17 percent constipation across tirzepatide doses. STEP 1 reported about 17 percent on Wegovy 2.4 mg. Pooled SUSTAIN/PIONEER data put Ozempic 1 mg at around 6 percent. So the trade-off is real, bigger appetite effect tends to mean bigger constipation effect.

Should I stop the GLP-1?

Not for routine constipation if it's manageable with the steps above. Reserve stopping or pausing for severe constipation, suspected pancreatitis (severe abdominal pain), or gastroparesis (persistent vomiting of old food). Most people manage with hydration + fibre + movement and keep the drug benefit.

Constipation when starting GLP-1: the fix

4 min readUpdated 2026-04-26By Dr Chad Okay

GLP-1 drugs (Ozempic, Wegovy, Mounjaro) slow gut transit on purpose, that's part of how they suppress appetite. The trade-off is constipation in 12-17 percent of users. The fix is layered: hydration, fibre type, movement, magnesium citrate, and (last resort) dose adjustment. Most people clear it in 1-2 weeks without losing the appetite benefit.

Constipation is the most common gut side effect of GLP-1 drugs. It's also one of the most misunderstood, most people throw bran at it and make it worse. Here's a sequenced plan that actually works.

Why GLP-1 drugs constipate

GLP-1 receptor agonists slow gastric emptying and reduce overall gut motility. This is the central mechanism for appetite suppression, food sits longer, fullness signals last longer, you eat less. The downside is that stools dry out by the time they reach the colon (more time means more water absorbed back into the bloodstream), and bowel movements become less frequent.

On top of this, most people on GLP-1s eat much less, so there's less stool volume to push through, and they often drink less because the appetite drop reduces fluid intake too.

Step 1, hydration (week 1)

The fastest fix. Aim for 2-2.5 litres a day. Set a glass-per-hour reminder if needed; most people drink less when their appetite drops. Drink before meals, not after. Add electrolytes (a pinch of salt + half a lemon in water) if regular water makes you nauseous.

Step 2, soluble fibre (week 1)

Add psyllium husk: 5-10 g in a glass of water once a day, separate from your main meals. Or: 30-50 g of oats in the morning. Or: 2 kiwi fruit (with skin if tolerated) at breakfast. These specifically help GLP-1 constipation because they form a gel that softens stool without adding bulk.

Avoid wheat bran and other purely insoluble fibres at this stage, they add bulk but can make slow-transit constipation worse.

Step 3, movement (ongoing)

Walk 30 minutes a day, ideally including a 10-minute walk after dinner. Movement directly stimulates the gut. People on GLP-1s who add 30+ minutes of daily walking report constipation rates 30-40 percent lower than sedentary GLP-1 users.

Step 4, magnesium citrate (week 2 if needed)

If steps 1-3 haven't worked by day 7, add 400-800 mg of magnesium citrate at bedtime. Magnesium citrate pulls water into the colon (osmotic effect) and softens stool by morning. It's safe for daily use, gentler than stimulant laxatives, and won't cause dependence.

Avoid magnesium oxide (poorly absorbed, often gives diarrhoea but doesn't improve overall regularity) and magnesium glycinate (good for sleep and cramps but doesn't help bowels).

Step 5, escalation if needed

Day 14, still constipated: lactulose 15-30 ml at bedtime. Adds osmotic effect from a different angle.
Day 21, still constipated: macrogol (Movicol, Laxido) 1-2 sachets daily. Reliably effective.
Day 30, still constipated: ask your prescriber about pausing escalation or stepping back to the previous dose. Some people need to stay on the lower dose for an extra month before escalating.
Don't stop the GLP-1 abruptly. Most constipation is dose-related; stepping back instead of stopping usually keeps the appetite benefit.
Stimulant laxatives (senna, bisacodyl) are last resort, useful for rescue but tolerance builds with daily use.

What probably won't help

Wheat bran or All-Bran cereal. Insoluble fibre on a slow-transit gut often worsens bloating without improving stool form.
Aloe vera juice or 'detox teas' with senna. Stimulant action causes cramping and tolerance.
Probiotics for constipation. Modest effect at best in this specific context.
Prune juice every day. Works once or twice but loses effect quickly.
Coffee enemas. No evidence, real risks.

When to call a doctor

No bowel movement for 7+ days despite the steps above.
Severe abdominal pain, especially with bloating that doesn't ease.
Vomiting, especially of food eaten the day before.
Blood in stool or bright red bleeding from the rectum.
Persistent nausea that's making it impossible to eat or drink.
Any sharp persistent abdominal pain on a GLP-1 drug warrants checking for pancreatitis or gallstones.

Common questions

Can I prevent it instead of treating it?: Largely yes. Start the hydration and soluble fibre routine the week BEFORE you start the GLP-1, not after constipation hits. Most people who do this either avoid significant constipation entirely or find it mild.
Will the constipation go away on its own?: Often yes, partially, after 4-6 weeks at each dose level as the gut adjusts. But it tends to come back at each dose escalation. Building the routine in step 1-3 above means you don't have to relearn it each escalation.
Is the constipation worse on Mounjaro than Ozempic?: Slightly. SURMOUNT-1 reported 12-17 percent constipation across tirzepatide doses. STEP 1 reported about 17 percent on Wegovy 2.4 mg. Pooled SUSTAIN/PIONEER data put Ozempic 1 mg at around 6 percent. So the trade-off is real, bigger appetite effect tends to mean bigger constipation effect.
Should I stop the GLP-1?: Not for routine constipation if it's manageable with the steps above. Reserve stopping or pausing for severe constipation, suspected pancreatitis (severe abdominal pain), or gastroparesis (persistent vomiting of old food). Most people manage with hydration + fibre + movement and keep the drug benefit.