How Long Does Lactulose Take To Work (And Why)?

Exact Answer: 48 Hours

Nowadays, in everyone’s busy life, people sometimes forget to take optimum care of themselves. Due to this, one might become prone to many diseases and illnesses. Constipation is one such condition that approximately 4 million people in the United States of America are suffering from. It is one of the most common digestive complaints that outnumbers all other chronic digestive conditions.

To relieve constipation among people, lactulose can be used. Lactulose is an osmotic laxative that is widely used for treating constipation. It is available as oral medicines or in small sachets and takes several hours to show its effects and start working.

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How Long Does Lactulose Take To Work?

The time that is taken by lactulose to improve constipation48 hours
The onset of action of lactulose24 – 48 hours
The elimination half-life of lactulose2 hours

Lactulose is taken to ease constipation condition but it can also help in treating severe liver disease called hepatic encephalopathy. As its name suggests, lactulose comes as a sweet syrup that one can swallow without any difficulty.

However, it must be noted that lactulose is not suitable for everyone. It should strictly not be administered to any children below the age of fourteen unless a qualified medical practitioner says so. Lactulose can be safely taken by adults and children above the age of fourteen. It does not harm breastfeeding women or those who are pregnant.

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Lactulose can be taken with or without food. It is advised by doctors to have it once or twice a day. The general dosage schedule is as follows. For adults – 15ml dose, for children (only if prescribed by a doctor) – 2.5 to 10ml dose, for babies (only is prescribed by a doctor) – 2.5ml dose.

However, if lactulose is being used for hepatic encephalopathy in adults, the usual dose is 30 to 50ml to be taken thrice a day. Lactulose takes about 48 hours i.e 2 entire days to start working. However, this could differ from person to person but the average time taken by lactulose to work is 24 – 48 hours.

Why Does Lactulose Take So Long To Work?

The constipation conditions can be relieved by regulating the bowel movements with the help of lactulose. Lactulose is nothing but a type of synthetic sugar compound that breaks down in the colon into substances that pull water towards itself which helps in softening the stools. In this way, it helps in treating constipation.

In hepatic encephalopathy patients, lactulose is used as an agent to reduce ammonia content in the blood of patients with liver diseases. This medication should be taken in exact doses as prescribed by a physician to avoid the possibility of experiencing side effects like gas, bloating, diarrhea, nausea, etc.

As lactulose is not absorbed in the bloodstream and does its work of drawing water into the lower bowel, it takes about 48 hours to evince its effects on the body. Lactulose is not classified as a fast-acting laxative as it takes at least 2 days to work.

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As lactulose is not fast to work it does not start working right after it is taken. When taken for treating constipation, at least 48 hours are required by the lactulose for softening stools to enable them to pass comfortably.

To ease constipation conditions and to facilitate the effective working of lactulose in one’s body, one should drink plenty of water i.e about 6 to 8 glasses to help lactulose work effectively and efficiently.


Lactulose is used to treat acute and chronic constipation and also liver diseases. It is a medication that does not cause significant harm if taken in excess. An overdose of lactulose can cause indigestion or stomach pain but such symptoms resolve in a day or two.

Lactulose takes about 48 hours to work and is advised to be taken twice a day, once in the morning and once at night, ensuring that there is a 10 – 12 hours gap between both doses in a single day. However, for liver problems, lactulose is to be taken 3 times a day. One should check the label on the medicine and follow it to the T to avoid any complications while using it.



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Hi! I'm Nidhi.

Here at the EHL, it's all about delicious, easy recipes for casual entertaining. So come and join me at the beach, relax and enjoy the food.

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