Ozempic constipation: the playbook

If you're on Ozempic, Wegovy, Mounjaro or Zepbound and you can't poo properly, you're in the majority of users at some point. It is one of the four most common GI side effects on semaglutide (after nausea, diarrhoea and vomiting, SUSTAIN/PIONEER pooled, Aroda 2023), and it gets worse with each dose increase. The good news is the fix is fairly mechanical.

Semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound) work partly by slowing gastric emptying. Food sits in your stomach longer, you feel full sooner, you eat less. That same braking effect carries on through the rest of the gut. Stuff moves more slowly through the small intestine and colon, which means more water gets reabsorbed, and the result is harder stool that's harder to pass.

On top of the mechanical slowdown, you're eating less. Less food in means less stool out. Less fibre means less bulk. Less fluid intake (because hunger and thirst signals get muddled) means even drier stool. All three pile on.

The mistake most people make is jumping straight to laxatives. Try these in order, give each one 48 to 72 hours, and stop at the first one that works.

1. Hydration. Around 2 to 2.5 litres a day suits most adults, and most GLP-1 users are quietly dehydrated because they do not feel thirsty. Set a phone reminder if you have to. If you have been given a fluid limit for heart or kidney reasons, that limit wins and this is a conversation for whoever set it.
2. Soluble fibre. Psyllium husk (Fybogel, Metamucil), taken with plenty of fluid. A pharmacist can advise on amounts. Soluble fibre forms a gel and softens stool. Do not start with insoluble fibre or wheat bran on a slowed gut (it tends to make bloating worse), and do not add fibre at all if you are passing nothing: bulk on a gut that has stopped moving makes things worse.
3. Movement. A 20 to 30 minute walk after the biggest meal of the day. Regular moderate activity like walking is linked with better colonic motility and faster transit in people with constipation. Daily, not just on bad days.
4. An osmotic laxative, which holds water in the colon so the stool stays soft. Guidelines put macrogol first (Movicol or Laxido in the UK, polyethylene glycol or Miralax in the US): the joint AGA and ACG guideline gives it a strong recommendation for chronic constipation, and magnesium oxide a conditional one. Magnesium oxide, not citrate, is the form the trials used, which is the opposite of the advice usually found online. On how much: supplemental magnesium is capped at 400 mg a day by UK guidance and 350 mg by the US limit, with diarrhoea as the effect that sets the ceiling. Going above that is using it deliberately as a laxative, and that is a conversation with a pharmacist or your prescriber rather than a number off a page, particularly if your kidneys are anything other than normal.
5. A stimulant laxative as a last resort. Senna or bisacodyl, occasional use only. These don't fix the cause, they force the colon. Fine for an emergency, not a long-term plan.

On GLP-1 you can't eat much, so what you do eat needs to count. Per meal, prioritise protein (to protect lean mass), soluble fibre (oats, kiwi, chia, ground flax, cooked apple, prunes), and a glass of water. Keep insoluble fibre (raw veg, salad, popcorn, wheat bran) modest because it adds volume without softening.

Constipation tends to spike for a week or two after each dose increase, then settle as your gut adapts. The escalation pattern matters. If you're rushing up the dose ladder to chase faster weight loss, you'll hit constipation harder. Slowing down by a week or two between dose steps is sometimes the kindest move on your gut, even if it feels like progress is slower.

Many people find the first 2 to 3 months of dose escalation are the hardest, with gut symptoms easing as the dose stabilises and the body adapts.

• Long-term stimulant laxative use. Senna and bisacodyl are intended for short-term use. Use them occasionally rather than as a daily fix, and speak to a pharmacist or doctor if you find you need them most days.
• High-dose insoluble fibre on a slow gut. Wheat bran and raw cruciferous veg can pile up if movement is sluggish.
• 'Detox teas'. Most are senna under another name. They are not a wellness intervention.
• Skipping meals to push more weight off faster. You'll constipate harder and lose lean mass.

This article is about comfort and everyday patterns, not medical guidance. Your doctor and pharmacist know you and your medicine; if anything about how you feel worries you, speak to them promptly, and if you ever feel seriously unwell, treat it as an emergency. The medicine's own patient information leaflet carries the important safety information and is worth reading in full.