The most effective first step for constipation is increasing your fiber intake to 25–38 grams per day while drinking at least 1.5 to 2 liters of water. If that doesn’t work within a few days, over-the-counter options like osmotic laxatives, magnesium, or prunes can get things moving. Here’s a practical breakdown of what works, how fast each option acts, and when to escalate.
Fiber: The Best Starting Point
Fiber increases the weight and size of your stool and softens it, making it easier to pass. Most adults don’t get nearly enough. The recommended daily intake is 25 grams for women under 50 (21 grams over 50) and 38 grams for men under 50 (30 grams over 50). If you’re well below those numbers, closing the gap will often resolve mild constipation on its own.
There are two types worth knowing about. Soluble fiber dissolves in water and forms a gel-like material that softens stool. You’ll find it in oats, beans, apples, and psyllium husk supplements. Insoluble fiber doesn’t dissolve. It adds bulk and helps push material through your digestive system. Wheat bran, vegetables, and whole grains are good sources. For constipation specifically, insoluble fiber tends to do the heavier lifting, but a mix of both is ideal.
One important caveat: fiber without enough water can actually make constipation worse. A study in patients with chronic functional constipation found that 25 grams of daily fiber increased stool frequency on its own, but the effect was significantly better when participants also drank 1.5 to 2 liters of water per day. If you’re adding a fiber supplement, increase your water intake at the same time.
Prunes: Surprisingly Well Studied
Prunes aren’t just an old folk remedy. They contain sorbitol, a natural sugar alcohol that draws water into the intestine, plus a decent amount of fiber. In a randomized controlled trial, eating about 80 grams of prunes per day (roughly 8 to 10 prunes) for four weeks significantly increased both stool weight and frequency compared to a water-only control group. Bumping up to 120 grams per day produced an even larger increase in stool weight. If you prefer something food-based before reaching for a supplement, prunes are one of the best-supported options.
Osmotic Laxatives
If fiber and dietary changes aren’t enough, osmotic laxatives are the next step most gastroenterologists recommend. These work by pulling water into your intestines, which softens stool and triggers movement. The most widely recommended one is polyethylene glycol 3350 (sold as MiraLAX and store-brand equivalents). You mix one heaping tablespoon into any beverage and take it once daily. It’s tasteless and dissolves easily.
The tradeoff is patience. Polyethylene glycol typically takes 2 to 4 days to produce a bowel movement, so it’s not a quick fix. It’s meant for short-term use, generally up to two weeks at a time. The joint guideline from the American Gastroenterological Association and American College of Gastroenterology gives polyethylene glycol a strong recommendation for chronic constipation in adults, making it one of the most evidence-backed options available over the counter.
Magnesium Supplements
Magnesium works similarly to osmotic laxatives by drawing water into the bowel. You can find it in several forms. Milk of magnesia (magnesium hydroxide) is a liquid, with one tablespoon providing about 500 mg of magnesium. Magnesium citrate and magnesium oxide come in pill form, typically 400 or 500 mg per pill. The upper limit is 1,500 mg per day.
Magnesium tends to act faster than polyethylene glycol, often within a few hours to overnight. Taking it at bedtime works well since it can make you sleepy. Magnesium oxide received a conditional recommendation in the 2023 gastroenterology guidelines for chronic constipation, placing it in the “likely helpful but less studied” category compared to polyethylene glycol.
Stimulant Laxatives
Stimulant laxatives are stronger. Rather than just softening stool, they cause the muscles in your intestinal wall to contract, physically pushing things along. Senna is the most common, available as tablets or tea. Take it at bedtime and it works in about 8 hours, producing a bowel movement by morning. Bisacodyl (sold as Dulcolax) works through a similar mechanism.
These are effective for occasional use when gentler options haven’t worked, and senna received a conditional recommendation in the 2023 clinical guideline. They’re not ideal for daily long-term use, though, because your bowel can become dependent on the stimulation. Think of stimulant laxatives as a backup rather than your first choice.
Probiotics
Probiotics are a slower, more indirect approach. Certain bacterial strains can help restore normal gut motility over time. Research in animal models of slow-transit constipation has shown that a combination of Bifidobacterium longum, Lactobacillus bulgaricus, and Streptococcus thermophilus significantly increased both stool frequency and intestinal motility while improving stool water content. The evidence in humans is growing but less definitive than for laxatives or fiber. Probiotics are worth considering if your constipation is chronic and you suspect your gut health is part of the picture, but they won’t provide fast relief.
A Practical Order of Operations
Gastroenterology guidelines lay out a clear progression. Start with the basics: more fiber from food or supplements, more water (aim for 1.5 to 2 liters daily), and regular physical activity. These nonpharmacological steps are the recommended first line of management.
If that doesn’t resolve things within a week or so, try an osmotic laxative like polyethylene glycol or magnesium. If you need faster overnight relief, a stimulant like senna is reasonable for short-term use. Prunes can slot in at any stage as a food-based supplement.
For chronic constipation that doesn’t respond to any of these, prescription medications exist that your doctor can discuss. The guidelines strongly recommend several prescription options for people who’ve tried over-the-counter treatments without success.
Warning Signs That Need Attention
Most constipation is uncomfortable but not dangerous. However, certain symptoms alongside constipation signal something more serious. Blood in your stool, unexplained weight loss, or vomiting combined with constipation all warrant prompt medical evaluation. If you haven’t had a bowel movement for a prolonged period and you’re experiencing severe abdominal pain or major bloating, that’s considered an emergency. These situations are uncommon, but they’re worth knowing about so you don’t dismiss them.