Why does constipation happen on tirzepatide?

Key Points:

• Constipation is a common side effect of tirzepatide (Mounjaro and Zepbound), caused by the medication slowing down digestion.
• Gastrointestinal (GI) issues are the most common side effects of these medications, and usually resolve once the body has adjusted to the highest individual dose.
• The most effective relief strategies involve strategically increasing both soluble fiber and fluid intake, especially since dehydration is also common.

Tirzepatide, the active ingredient in medications like Zepbound® and Mounjaro®, is highly effective in helping people achieve significant and sustained weight loss. But it comes with some unpleasant side effects, including constipation.

If you are experiencing constipation while taking tirzepatide, know that you are not alone. Gastrointestinal (GI) issues are the most common adverse events reported in clinical trials, and constipation is a significant concern for many users.

The good news is that for most people, this side effect is manageable and often resolves as the body adjusts to the medication. By understanding why tirzepatide affects your digestive system and applying simple, strategic nutrition advice, you can find effective relief. Let’s get into it.

Why is constipation so common on tirzepatide?

When you feel constant discomfort and sluggishness, you might be wondering why tirzepatide is causing such a slowdown.

The constipation stems directly from the drug’s primary mechanism of action.

The dual-action hormone mechanism

Tirzepatide is a unique medication because it is a dual receptor agonist, meaning it mimics the action of two different natural hormones in your body: glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP).

While both hormones work together to help manage blood sugar and signal fullness to your brain, the GLP-1 component is responsible for affecting your gut movement. Activating the GLP-1 receptor slows the movement of food through the stomach and small intestine.

This mechanism is crucial for prolonged satiety and weight loss, helping you feel fuller sooner and for longer, but it has a ripple effect through your entire digestive system. When the contents of your intestine move too slowly, your colon absorbs more water from the stool, leading to harder, drier, and less frequent bowel movements.

Studies confirm that tirzepatide significantly increases the risk of developing constipation.

“Tirzepatide may cause constipation because it slows digestion and intestinal movement, allowing more water to be absorbed from the stool and making it harder to pass,” says Allison Stanton, RD.

“Tirzepatide also reduces appetite, often leading to lower fiber and fluid intake which can make constipation worse.”

The side effect cycle: low appetite & low intake

It’s important to remember that tirzepatide works by suppressing your appetite and increasing satiety. While this is the goal, it creates a secondary problem for your digestive health.

Many people on tirzepatide experience:

• Decreased food intake: You’re eating less, which means you’re consuming less overall fiber and bulk – the material your digestive system needs to create a soft, passable stool.
• Reduced fluid intake: You may also be drinking less water throughout the day because you don't feel thirsty, leading to dehydration. Constipation gets significantly worse when there isn't enough fluid to soften the stool.

This creates a cycle where the intentional slowing of your gut (the drug's action) combines with low fiber and low fluid intake (a side effect of appetite loss), making constipation almost inevitable for some people.

Evidence-based strategies to relieve tirzepatide constipation

The good news is that the core strategy for managing tirzepatide-related constipation is simple: add back what the drug takes away. Since the GI adverse events are often mild-to-moderate and transient as your body adjusts, a focused nutritional approach can make a huge difference.

1. Start with strategic fiber intake

For adults, the generally recommended goal for daily fiber intake is 25 to 30 grams (g) or more, though exact goals vary by age and sex. However, most adults only get about 16 to 17g daily.

When on tirzepatide, you need to be strategic because increasing fiber too quickly can cause uncomfortable gas and bloating, which can feel much worse with slowed digestion.

• Go low and slow: Gradually increase your fiber intake by just one or two grams per day over a week.
• Prioritize soluble fiber: Soluble fiber dissolves in water to form a gel-like substance that keeps stool soft. Good food sources include oats, beans, apples, carrots, and barley.
• Choose easy-to-digest sources: Since nausea and loss of appetite are common, opt for cooked or pureed vegetables (like a smooth carrot soup or cooked spinach) instead of raw salads or tough skins. These foods are easier on your digestive system but still provide soluble fiber. Even half a cup of cooked legumes, like lentils or chickpeas, can provide a high fiber count.

2. Prioritize hydration

This is perhaps the most critical step. Fiber only works when it has enough water to absorb. Without adequate hydration, increasing fiber can actually make your constipation worse.

The trick is to overcome the lack of thirst signal caused by the medication:

• Use non-water fluids: If drinking plain water feels difficult, try different options. Herbal teas, vegetable broths (which also provide sodium and potassium), or lightly flavored waters can help you hit your fluid goals.
• Set a schedule: Don't wait until you feel thirsty. Aim to drink a full glass of fluid (8-10 ounces) every time you take your medication, sit down for a meal, or get up from your desk.
• Watch for dehydration red flags: Gastrointestinal side effects like vomiting and diarrhea, which are also common with tirzepatide, can lead to fluid loss and dehydration. This can be serious, potentially leading to acute kidney injury, so staying on top of your fluid intake is essential.

3. Get moving to get things moving

Physical activity is a natural laxative. When you move your body, you stimulate the muscles in your intestinal walls, which helps push food and waste through your digestive system.

The movement does not need to be strenuous. A post-meal walk for even 10-15 minutes can help fire up your digestive process. You should also incorporate gentle activity like a daily walk, yoga, or cycling, as well as aim for at least 150 minutes of moderate-intensity activity each week.

4. Optimize your bathroom routine

Your body has a natural reflex called the gastrocolic reflex – a wave of muscle contractions in the colon that often occurs after eating.

You can capitalize on this reflex by trying to use the bathroom around 30 minutes after your breakfast. This can give you the best chance to pass a bowel movement. It can also be helpful to use a small stool to elevate your feet while sitting on the toilet, which positions your body in a way that makes passing stool easier and more complete.

When to try over-the-counter options

Sometimes, even the best nutritional habits aren't enough to counteract the significant effect of the medication on your gut motility. In these cases, over-the-counter (OTC) options, used in consultation with your healthcare provider, can provide necessary relief.

OTC solutions

When recommending OTC products, healthcare providers often start with a bulk-forming agent or an osmotic laxative:

• Psyllium husk (bulk-forming): A common soluble fiber supplement that adds bulk to your stool. It is often the first-line recommendation, but remember to take it with plenty of water.
• Osmotic laxatives (e.g., polyethylene glycol/Miralax, magnesium citrate): These work by drawing water into the colon, softening the stool and promoting movement. They are often highly effective for the hard, dry stools associated with tirzepatide constipation.
• Stool softeners (e.g., docusate sodium): These add moisture to the stool, making it easier to pass.
• Stimulant laxatives (e.g., Senna): These cause the muscles in the colon to contract. They are typically reserved for short-term, acute relief and should be used sparingly and only as directed by a healthcare professional.

When to call your healthcare provider

While most tirzepatide-related constipation is mild, serious and rare GI issues have been reported. It is crucial to monitor your symptoms and reach out to your healthcare provider immediately if you experience any of the following:

• Severe, progressive, or unrelieved abdominal pain
• Inability to pass gas or have a bowel movement for several days, despite using OTC treatments
• Rectal bleeding
• Nausea and vomiting that prevent you from keeping fluids down (a sign of potential dehydration)
• Abdominal distension (severe bloating)

Working with a dietitian to handle GLP-1 side effects

Managing constipation on tirzepatide is about far more than just taking fiber – it requires personalized nutritional strategy to manage a complex change in appetite, satiety, and gut function.

This is where a registered dietitian – a board-certified expert in medical nutrition therapy – becomes an invaluable part of your healthcare team.

“To help prevent constipation while taking tirzepatide, drink at least 64 oz of water daily and aim for 25 grams of fiber daily from fruits, vegetables, whole grains and legumes,” says Allison Stanton, RD. “Daily exercise is also key, as physical activity helps stimulate bowel movements.”

A registered dietitian can help you navigate the nuanced reality of GLP-1 therapy:

1. Personalized fiber plans: An RD can determine the exact amount of fiber your body needs and create a food-first plan that accounts for your nausea and reduced appetite, recommending low-volume, nutrient-dense foods that won't exacerbate your side effects.
2. Micronutrient management: With a reduced food intake, you’re likelier to have some micronutrient deficiencies. A dietitian ensures your smaller meals are balanced and nutrient-dense, supporting overall health and energy.
3. Hydration strategies: They can help you create a concrete hydration schedule and suggest easy-to-tolerate fluids to protect against dehydration.
4. Meal timing: They can work with you to plan consistent meal times that optimize your hunger cues and manage other common GI issues, like acid reflux or nausea.

Tirzepatide is a powerful tool for weight management and metabolic health, but achieving the best, most comfortable results depends on pairing it with the right lifestyle support. You don't have to navigate the discomfort of constipation alone.

Final Thoughts

Tirzepatide (Mounjaro/Zepbound) offers a path to significant health improvements, but the gastrointestinal side effects, particularly constipation, are a real challenge. You can be assured that this is a known, expected, and manageable part of the treatment journey.

The most effective strategy relies on consistent hydration (drinking adequate fluids, even when not thirsty), a gradual, strategic increase in fiber (prioritizing easy-to-digest sources), and regular movement. Remember that GI side effects often lessen over time as your body adapts to the medication.

For a customized plan that manages your symptoms, addresses your unique dietary needs, and supports your overall health goals, consider working with a specialist.

Find a registered dietitian who accepts your insurance and get the personalized guidance you need to thrive on tirzepatide.

The views expressed by authors and contributors of such content are not endorsed or approved by Fay and are intended for informational purposes only. The content is reviewed by Fay only to confirm educational value and audience interest. You are encouraged to discuss any questions that you may have about your health with a healthcare provider.