Can water help with constipation?

2026-10-30

Yes, but mostly as fiber's partner. If you're short on fluids, drinking more can soften stools, and in one trial people eating about 25 g of fiber a day had noticeably more bowel movements when they also drank 1.5–2 liters (50–68 fl oz) of water. If you're already well hydrated, extra water on its own is unlikely to fix constipation. The combination that works for most people is enough fiber, enough fluid, and regular movement.

Why fluid matters for your bowels

Your large intestine's main job is to absorb water from digested food. The longer stool stays there, the more water is pulled out and the harder and drier it becomes. When you don't drink enough, your body holds on to water more tightly, which can make stools harder to pass.

Fiber works by holding water in the stool. Soluble fiber (oats, beans, fruit) forms a gel; insoluble fiber (wheat bran, whole grains, vegetable skins) adds bulk. Both need water to do their job. That's why the NIDDK puts it simply: eat enough fiber and drink plenty of liquids to help the fiber work better.

What the evidence shows

Water plus fiber

The clearest study is an Italian randomized trial by Anti and colleagues (1998). It included 117 adults aged 18–50 with chronic functional constipation. For two months, everyone ate a diet with about 25 g of fiber a day. One group was asked to drink 2 liters of mineral water a day (they averaged 2.1 liters); the other drank as they liked (about 1.1 liters). Both groups improved, but stool frequency rose significantly more, and laxative use fell more, in the group that drank more. The authors concluded that fiber's effect "can be significantly enhanced by increasing fluid intake to 1.5–2.0 liters/day".

Fiber on its own

A 2016 meta-analysis of randomized trials pooled seven trials and found that fiber supplements increase stool frequency in adults with chronic constipation compared with placebo. The effect was moderate and the trials were small. Fiber is the main lever; water helps it work.

Water on its own

There's little good evidence that drinking more than you need helps if you're already well hydrated. Your kidneys pass the excess as urine; it doesn't go to your colon. So if you already drink enough and your urine is pale, the next step is usually more fiber or more activity, not more water.

The evidence base is modest — a few trials, not many — but it fits with how digestion works, and the advice is low-risk for most people.

A practical plan

1. Check your fluid intake

As a reference, the European Food Safety Authority considers about 2.0 liters of total water a day adequate for women and 2.5 liters for men, from food and drinks combined; around 70–80% of that usually comes from drinks. Pale yellow urine through the day is a good sign you're getting enough. More detail in how much water should you drink a day?

If you've been drinking far less, increase gradually: add a glass with each meal and one between meals.

2. Increase fiber slowly

Most adults need roughly 22 to 34 g of fiber a day, depending on age and sex, according to the NIDDK. Many people eat much less. Good sources:

oats, whole-grain bread and cereals, brown rice;
beans, lentils, chickpeas;
fruit like pears, apples, berries and kiwi, and dried fruit like prunes;
vegetables, especially with the skin on;
seeds such as linseed (flaxseed).

Add fiber over a couple of weeks rather than all at once. A sudden jump can cause gas and bloating. And as you add fiber, add fluid with it.

3. Move

Regular physical activity, even a daily walk, helps stool move through the gut. The NHS suggests a daily walk or run alongside fluid and fiber.

4. Don't ignore the urge

The NHS advises not delaying when you feel the urge, and keeping to a regular time and place with plenty of time. Many people find the time after a meal, often breakfast, works best, since eating stimulates the bowel.

5. Give it time

Diet and lifestyle changes can take a few days to a few weeks to work, according to the NHS. If they're not enough, a pharmacist can suggest a laxative for short-term use.

Do coffee and other drinks help?

Coffee stimulates the colon in many people, and it counts toward your daily fluid. Tea, milk, soups and water-rich fruit count too. Alcohol is the exception: the NHS advises avoiding it when you're constipated. For which drinks count toward your water goal, see do coffee, tea, milk and juice count?

When to see a doctor

Constipation is common and usually harmless, but the NHS advises seeing a GP if:

it doesn't improve with treatment or keeps coming back;
you have blood in your stool or unexplained weight loss;
you feel tired all the time as well;
you have regular bloating or tummy pain;
your bowel habits change suddenly;
it's caused by a medicine, such as opioid painkillers (don't stop a prescribed medicine without asking first).

Also talk to a doctor before increasing fluids significantly if you have heart or kidney disease or have been told to limit fluids, and for constipation in babies, during pregnancy, or in older adults on several medications. Constipation is a common side effect of low fluid intake in older adults too.

Keeping both habits going

The changes that help constipation only work if you keep them up. If you tend to forget to drink during the day, a tracker can help. Water Tracker gives you a daily goal based on your weight and activity, lets you log a glass in one tap from your iPhone, Apple Watch or a widget, and sends reminders that go quiet once you reach your goal. Weekly charts make it easy to see whether you're drinking consistently, which is what matters when you're adding fiber. For more ways to build the habit, see 15 easy ways to drink more water.

Bottom line

Water helps with constipation mainly by letting fiber do its job. Aim for 22–34 g of fiber a day, increased gradually, enough fluid to keep your urine pale, and regular movement. If you already drink enough, more water alone is unlikely to help. See a doctor if constipation persists, keeps coming back, or comes with blood, weight loss or pain.

This article is general information, not medical advice. If you have a health condition, are pregnant or take medication, ask your doctor how much you should drink.