How Much Magnesium Citrate for Constipation?

Constipation occurs when you go an abnormally long period of time without a bowel movement. Constipation can be caused by a lack of fiber in your diet, as a result of dehydration or due to certain medications. One treatment for constipation is magnesium citrate, a laxative that can be purchased without a prescription.

A pile of laxative pills. Credit: Kwangmoozaa/iStock/Getty Images

How Does It Work?

Magnesium citrate is a type of laxative known as a hyperosmotic laxative. When you consume magnesium citrate, it passes through your digestive tract and pulls water from the surrounding tissues into your intestines. The increase in water stimulates contraction of the muscles around your intestines, resulting in the muscles propelling fecal material forward. The water also helps to soften fecal material that may have gotten dried out and stuck.

Magnesium Citrate Dosing

Magnesium citrate comes as a liquid. For an adult the standard dose is 240 mL, which is approximately one cup. For children between the ages of 6 and 12, the standard dose is 50 to 100 mL, which is approximately 1/4 to 1/2 of a cup. For children between the ages of 2 and 6, the recommended dose is 4 to 12 mL, which is approximately 1 to 3 tsp.


If you are taking magnesium citrate, you can mix the liquid with water or juice. A full dose of magnesium citrate will result in a bowel movement within a half-hour to three hours, though smaller doses may take longer to produce a bowel movement. You can take magnesium citrate with food, but it may take longer for the drug to have an effect. Be sure to drink two full glasses of water or some other liquid after taking magnesium citrate to replace some of the water your body will lose.

Side Effects

Although magnesium citrate is safe for most people to use, it can cause some side effects. For example, you may develop diarrhea after taking magnesium citrate. Other side effects include bloating, flatulence, anal irritation, abdominal cramping, sweating and weakness. Magnesium citrate can cause you to become dehydrated and develop electrolyte imbalances, which can lead to dizziness, fainting and heart palpitations. If you experience any of these symptoms, contact your doctor and stop taking magnesium citrate.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.
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