If you’re struggling to have a bowel movement, the fastest over-the-counter options are osmotic laxatives and stimulant laxatives, which can work in as little as 30 minutes to 12 hours depending on the type. But the best choice depends on whether you need quick relief right now or a longer-term fix for ongoing constipation. Here’s what actually works, how fast each option acts, and what to try first.
Start With Fiber and Fluids
Before reaching for a laxative, it’s worth checking whether your diet is working against you. Most adults need between 22 and 34 grams of fiber per day (women on the lower end, men on the higher end), and the average American falls well short of that. Fiber adds bulk and moisture to stool, making it easier to pass. Good sources include beans, whole grains, vegetables, and fruits.
Hydration matters more than people realize. A large study of over 14,000 adults found that people who drank the least fluid had nearly double the constipation risk compared to those who drank the most. The relationship was dose-dependent: every increase in daily fluid intake corresponded to lower constipation rates. Water, coffee, tea, and water-rich foods all count toward your total. If you’re adding more fiber to your diet, increasing your water intake at the same time is essential, since fiber without adequate fluid can actually make things worse.
Prunes: A Surprisingly Effective First Choice
Dried prunes outperform some pharmacy options. In a clinical trial comparing prunes to psyllium husk (the active ingredient in Metamucil), prunes produced significantly more complete bowel movements per week and better stool consistency. Both were equally well tolerated, but prunes came out ahead on the measures that matter most. Eating about 5 to 10 prunes a day, or drinking a glass of prune juice, is a reasonable starting point. Researchers have suggested prunes should be considered a first-line option for mild to moderate constipation.
Bulk-Forming Laxatives
Psyllium husk (sold as Metamucil) and methylcellulose (Citrucel) are bulk-forming laxatives. They work by absorbing water in the intestine, which makes stool larger, softer, and easier to move along. These are the gentlest pharmacy option and are safe for daily, long-term use. The tradeoff is speed: they typically take one to three days to produce results. If you need relief tonight, this isn’t your best bet. But for preventing constipation from recurring, they’re a solid foundation.
Osmotic Laxatives
Osmotic laxatives pull water into the intestine, softening stool and triggering a bowel movement. Two common options sit on pharmacy shelves.
Polyethylene glycol 3350 (MiraLAX) is one of the most studied. In clinical trials, 42% of patients met treatment goals compared to just 13% on placebo. Most people see results within one to three days, and bowel frequency improves significantly within the first week. It’s tasteless, mixes into any liquid, and is generally well tolerated over months of use.
Magnesium citrate works faster, often within 30 minutes to 6 hours. It’s sold as a liquid in most pharmacies and is a good option when you want same-day relief. Drink it with a full glass of water. Because it’s more potent, it’s better suited for occasional use rather than a daily routine.
Stimulant Laxatives
Stimulant laxatives like bisacodyl (Dulcolax) and senna (Senokot) are the strongest over-the-counter options. They work by triggering contractions in the intestinal wall while also reducing how much water the bowel absorbs from stool. Taken orally, they produce a bowel movement within 6 to 12 hours. Bisacodyl suppositories work much faster, typically within 15 to 60 minutes.
These are effective for short-term use, but they aren’t meant to be a daily habit. Bisacodyl is generally not recommended for longer than four weeks due to potential effects on the colon over time. If you find yourself relying on stimulant laxatives regularly, that’s a sign to look at other approaches or talk with a provider.
Why Stool Softeners May Disappoint
Docusate sodium (Colace) is one of the most commonly recommended stool softeners, but the evidence behind it is surprisingly weak. A review of the clinical research found that four out of five studies showed docusate was no more effective than placebo at increasing stool frequency, softening stool, or reducing straining. Even in people taking opioids, a population especially prone to constipation, docusate performed no better than a sugar pill. If you’ve tried Colace without success, you’re not alone. Switching to an osmotic laxative or increasing fiber will likely give you better results.
Probiotics for Ongoing Constipation
If constipation is a recurring problem rather than a one-time event, probiotics containing Bifidobacterium or Lactobacterium species may help. A meta-analysis of randomized controlled trials found that these probiotics increase stool frequency by about 0.8 bowel movements per week and reduce the time it takes food to travel through the gut by roughly 15 hours. Products containing both Bifidobacterium and Lactobacillus showed the strongest effect on transit time. Interestingly, the specific strain, number of strains, and daily dose didn’t seem to matter much. The benefit was consistent across a range of products.
Probiotics won’t give you relief in the next few hours, but over weeks of regular use, they can shift your baseline toward more regular movements.
Movement Helps Move Things Along
Physical activity stimulates the gut through two pathways. First, exercise activates the parasympathetic nervous system, which directly increases intestinal contractions. Second, the physical bouncing and vibration of activities like walking, jogging, or even using a vibration platform help push stool through the lower colon toward the rectum, which triggers the local reflexes that make you feel the urge to go. Even a 15 to 20 minute walk can make a noticeable difference, especially in the morning.
Choosing the Right Option for Your Situation
Your best choice depends on how urgent the problem is:
- Need relief within an hour: A bisacodyl suppository or magnesium citrate liquid.
- Need relief by tomorrow: An oral stimulant laxative like senna or bisacodyl taken at bedtime, or magnesium citrate.
- Need relief within a few days: Polyethylene glycol 3350 (MiraLAX), prunes, or a psyllium-based fiber supplement.
- Want to prevent constipation long-term: Daily fiber (from food or supplements), adequate fluids, regular exercise, and possibly a probiotic.
If you’ve had constipation lasting longer than three weeks, notice blood in your stool, experience severe abdominal pain, or have unexplained weight loss, those are signs that something beyond a simple laxative may be needed.