Constipation is one of the most common side effects people notice on GLP-1 medications like semaglutide and tirzepatide. It's usually manageable with a few steady habits. Fiber, fluids and movement are the foundation, and your care team can help if those aren't enough.
Key takeaways
- GLP-1 drugs slow digestion, and eating and drinking less can add to constipation.
- Most adults need 22 to 34 grams of fiber a day, according to NIDDK.
- Add fiber slowly and drink more fluids as you do, or it can make bloating worse.
- Movement, regular meals and routine bathroom timing help.
- If home steps don't work, ask your prescriber or pharmacist about other options. Get care fast for severe belly pain or vomiting.
Why GLP-1s can cause constipation
GLP-1 medications slow how fast your stomach empties and can slow movement through the gut. That helps you feel full, but it can also make stools harder to pass. Other common factors:
- Smaller meals mean less bulk moving through
- Less fluid, especially if thirst is lower or you're busy
- Fewer fiber-rich foods if you're focusing on protein or eating less overall
- Less activity on days you feel tired or queasy
A 2025 joint advisory on nutrition during GLP-1 therapy recommended managing constipation early, with adequate fluids and a gradual increase in fiber from foods.
How much fiber do you need?
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) says adults should aim for 22 to 34 grams of fiber a day, depending on age and sex. Many Americans get far less.
There are two main types:
- Soluble fiber absorbs water and forms a gel. It helps soften stool. Found in oats, beans, lentils, apples, citrus and chia.
- Insoluble fiber adds bulk and helps move things along. Found in whole grains, wheat bran, nuts and many vegetables.
Most fiber-rich foods have some of both.
Fiber-rich foods that fit a smaller appetite
| Food | Portion | Approx. fiber |
|---|---|---|
| Raspberries | 1 cup | about 8 g |
| Lentils, cooked | 1/2 cup | about 8 g |
| Black beans, cooked | 1/2 cup | about 7 to 8 g |
| Chia seeds | 1 tablespoon | about 4 g |
| Pear, with skin | 1 medium | about 5 to 6 g |
| Oatmeal, cooked | 1 cup | about 4 g |
| Prunes | 5 prunes | about 3 g |
| Broccoli, cooked | 1/2 cup | about 2 to 3 g |
Values are approximate. Check labels when you can. Beans and lentils are especially useful because they bring both fiber and protein. See high-protein foods for a small appetite for more ideas.
Add fiber the gentle way
Jumping from low fiber to high fiber overnight can cause gas, cramping and bloating, which can feel worse on a GLP-1. Instead:
- Add one fiber-rich food at a time, for example a pear at lunch or chia in yogurt.
- Increase over a couple of weeks, not a couple of days.
- Drink more fluids at the same time. NIDDK notes that liquids help fiber work better and keep stools soft. See hydration on GLP-1 medications.
- Notice your triggers. The joint advisory noted that high-fat or very high-protein meals can slow digestion more, so balance plates with produce and whole grains.
Other habits that help
- Move daily. A short walk after meals can help the gut keep moving.
- Eat at regular times. A steady routine supports regular bowel habits.
- Don't ignore the urge. Give yourself time in the bathroom, especially after breakfast.
- Track patterns. Logging meals, fluids and bowel movements in the PepSteady app can show what helps.
When food isn't enough
If diet changes don't do the job, there are over-the-counter options, such as fiber supplements, polyethylene glycol (PEG 3350) and stool softeners. The 2025 advisory also mentions magnesium in some cases. These aren't right for everyone. Magnesium, for example, may not be safe with kidney disease. Ask your pharmacist or prescriber what fits you, including how they fit with your other medicines.
When to get medical help
Contact your prescriber if constipation lasts several days despite home care. Get care right away for:
- Severe or constant belly pain
- Vomiting, especially if you can't keep fluids down
- A hard, swollen belly or not passing gas
- Blood in your stool or black, tarry stools
GLP-1 labels list serious problems like pancreatitis, gallbladder disease and, rarely, bowel blockage, so don't wait on severe symptoms. See when to call your doctor or 911.
A sample high-fiber day
Here is one example of how food choices can add up. Amounts are approximate.
- Breakfast: 1 cup oatmeal with 1 tablespoon chia seeds and a few raspberries (about 10 g)
- Lunch: lentil soup, 1/2 cup lentils (about 8 g), with a small side salad (about 2 g)
- Snack: 1 medium pear with the skin (about 5 g)
- Dinner: grilled fish or tofu with 1/2 cup broccoli (about 2 g) and 1/2 cup black beans (about 7 g)
That comes to about 34 grams. If you currently eat much less fiber, build up to a day like this over a few weeks, not all at once.
The bottom line
Constipation on a GLP-1 is common and usually manageable. Slowly work up toward 22 to 34 grams of fiber a day, drink more fluids, stay active and keep a routine. If that isn't enough, your pharmacist or prescriber can recommend next steps, and severe symptoms always need prompt care.
Sources
- NIDDK: Eating, diet and nutrition for constipation
- Nutritional priorities to support GLP-1 therapy for obesity: A joint advisory (2025), PMC
- Zepbound (tirzepatide) U.S. Prescribing Information, Eli Lilly
Frequently asked questions
Why do GLP-1 medications cause constipation?
GLP-1 drugs slow how quickly food moves out of the stomach and through the gut. Eating less food and drinking less fluid can also play a part. Constipation is listed as a common side effect on the labels for these drugs.
How much fiber should I eat?
The NIH's digestive disease institute says most adults should get 22 to 34 grams of fiber a day, depending on age and sex. Increase it slowly and drink more fluids as you do.
When should I call my doctor about constipation?
Call if you haven't had a bowel movement in several days despite home steps, or if you have severe belly pain, vomiting, a swollen belly, or blood in your stool. Severe belly pain can signal other serious problems and needs prompt care.