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Different types of laxatives work in different ways, begin working at different times, and stay in the body for varying amounts of time, from minutes to days.
- Laxatives are medications that treat constipation by stimulating a bowel movement.
- Some laxatives take effect within 15-30 minutes, while some can take 48-72 hours.
- Bulk-forming laxatives stop working after passing one stool, while other laxatives start weakening 2-16 hours after peak concentration.
There are many different types of laxatives available.
We explain the differences in how long each type of laxative takes to work, as well as more information regarding each laxative type.
The table below shows how long each type of laxative takes to work. Out of the different types, suppositories work the fastest, between 15 to 30 mins.
|Type of laxative
|How long does it take to work?
|12 to 72 hours
|12 to 24 hours (some effect)
48 to 72 hours (full effect)
|6 to 8 hours
|48 to 72 hours (lactulose)
30 minutes to 3 hours (saline)
6 hours or longer (polymer)
|6 to 12 hours
|15 to 30 minutes
The amount of time that a medication spends in your system can depend on the active ingredient, the dose given, and the route in which it leaves the body.
Sometimes this information is expressed as a drug’s half-life, or the amount of time it takes for 50 percent of the drug to leave your system.
The active ingredients of laxatives can have different half-lives. For example, the half-life of lactulose is about 2 hours while the half-life of bisacodyl is 16 hours. Bulk-forming laxatives don’t have a half-life, because they’re eliminated with your next bowel movement.
If you’re worried about the amount of time a laxative will spend in your system, you should raise these concerns with a doctor or pharmacist.
Emollient laxatives are also referred to as stool softeners.
Emollients take 12 to 72 hours to work. They work to soften your stool by adding moisture to it. Softer stools are easier to pass.
The active ingredient of emollient laxatives is a compound called docusate.
Examples of emollient laxative products include Colace and Surfak.
Bulk-forming laxatives function similarly to the fiber that you obtain from your diet.
They promote the absorption of water into your bowels. This makes stools larger and softer which in turn makes them easier to pass.
They take 12 to 24 hours for some effect and 48 to 72 hours for their full effect.
The active ingredients of bulk-forming laxatives can include psyllium, methylcellulose, and sterculia.
Examples of bulk-forming laxative products include Metamucil and Benefiber.
Lubricant laxatives promote the passage of stool through the bowel by coating the stool in a waterproof film. This allows the stool to both hold on to its moisture and to move more easily through the bowel.
Lubricant laxatives take 6 to 8 hours to take effect.
Mineral oil is an example of a lubricant laxative.
Hyperosmotic laxatives function by increasing the amount of fluid that’s in your bowels. This increase in fluid can help soften stool and promote its passage through the bowel.
There are several different types of hyperosmotic laxatives and they’re divided up by active ingredients.
The active ingredient in lactulose laxatives is a sugar-like compound.
Lactulose laxatives are often used for treatment of long-term or chronic constipation. This type takes 48 to 72 hours.
Examples of lactulose laxative products include Enulose and Generlac.
These laxatives are made up of salts in liquid. They’re used as a short-term treatment for constipation.
Saline takes 30 minutes to 3 hours to work. Examples of saline laxatives include Phillips’ Milk of Magnesia and Royvac.
Polymer laxatives are made up of large molecules such as polyethylene glycol. Like saline laxatives, polymer laxatives are used for the short-term treatment of constipation.
Examples of polymer laxative products include MiraLAX and PegaLAX. Polymers take 6 hours or longer to work.
Stimulant laxatives cause the muscles of your bowels to contract. This allows stool to pass more readily through your bowels.
This type of laxative can take 6 to 12 hours to work.
The active ingredients of stimulant laxatives can include senna, bisacodyl, and sodium picosulphate.
Examples of stimulant laxative products include Dulcolax and Ex-Lax.
A suppository is a medication that’s inserted into your rectum. Once inserted, the medication dissolves and enters the bloodstream.
Depending on the active ingredient, suppositories can work to either soften the stool or to stimulate the muscles of your bowels in order to better ease movement of stool.
Suppositories work the fastest, within 15 to 30 minutes.
The active ingredients bisacodyl and glycerol can be given as suppositories to treat constipation.
Examples of available suppository medications include Dulcolax and Fleet Glycerin.
There are some risks that you should be aware of when you use laxatives. These can include:
Dehydration or electrolyte imbalance
Because many laxatives work by drawing water into your bowels, you should be sure to drink plenty of water while you’re taking them. If you don’t you may become dehydrated or develop an electrolyte imbalance.
Interactions with other medications
Be sure to read labels carefully when selecting a laxative. Some medications, such as antibiotics and heart medications, can interact in a negative way with laxatives.
If you’re unsure which laxative to take, consult your doctor.
Decrease in bowel motility
Using laxatives frequently can cause a dysfunction in the natural movement of your bowels.
You should always be sure to use laxatives in moderation. If you find that you have to use laxatives often to have a bowel movement, you should visit your doctor to discuss your concerns.
Pregnancy and breastfeeding considerations
If you’re pregnant you should speak to your doctor before taking laxatives. Some laxatives, such as stool softeners or bulk-forming laxatives, are safe for pregnant women while others aren’t.
Most laxatives are safe to take while breastfeeding, however you should still talk to your doctor before using them.
Some laxative ingredients can pass to the infant via breast milk and cause diarrhea.
There are a variety of laxatives available to treat constipation. Some laxatives are better for short-term treatment of constipation while others are more ideal for treating long-term or chronic constipation.
You should always consult your doctor if you’re unsure which laxative should be used for your constipation.
You can also help to avoid becoming constipated by following some of the tips below:
Increase fiber intake
Increase the amount of fiber in your diet. Fiber helps to improve bowel function.
Be sure to get enough fruits, vegetables, and whole grains. Here are 22 high-fiber foods you should eat.
Having enough fluids can help ease the passage of bowel movements.
You should aim for 8 glasses of water per day while avoiding things such as caffeine and alcohol. Here are 16 reasons to drink more water.
Making sure that you exercise regularly can help stool to move more effectively through your bowels. Here are 6 ways to live a more active life.
Don’t hold it
If you feel like you have to have a bowel movement, be sure to go at your earliest convenience. Don’t hold it in.