How long does magnesium citrate take to work?

If you're dealing with constipation – that uncomfortable feeling when it's hard to go to the bathroom – your doctor or pharmacist might suggest magnesium citrate. Magnesium citrate typically works within 30 minutes to 6 hours after consumption, but how fast it acts on your system can vary. It's a common over-the-counter remedy, usually sold as a liquid drink.

What is Magnesium Citrate and How Does it Help?

Magnesium citrate is a type of medicine called a "saline laxative." When you drink it, it works to relieve constipation by pulling more water into your intestines. This extra water softens the stool, making it easier to pass. It also helps get your bowels moving. It's typically used for temporary relief when you're constipated once in a while.

How Fast Does Magnesium Citrate Work?

So, how long does it take? According to the information provided with magnesium citrate liquid products, you can generally expect it to cause a bowel movement anywhere from 30 minutes to 6 hours after you drink it.

This is a fairly wide window because everyone's body is different. Several things can affect how quickly it works for you:

• Your own body: How your digestive system works naturally plays a role.
• How much you take: Follow the dosage instructions on the package or given by your doctor.
• Hydration level: Drinking plenty of water is important when using magnesium citrate. The package directions usually tell you to drink a full glass (8 ounces) of liquid with each dose.

How to Know If Magnesium Citrate Is Working?

Here are the early signs that magnesium citrate is taking effect:

• Gurgling or cramping in your lower abdomen
• Increased urgency to use the bathroom
• Passing loose or watery stools
• Feeling the need to stay near a restroom

How Long Does Magnesium Citrate Take To Wear Off?

Once it starts working, the active laxative effect—meaning the period where you'll likely experience bowel movements—can continue for several hours. For most people, the effects start to wear off after about 4 hours. The effects gradually lessen. You'll notice the urgency and frequency of bowel movements decrease as the extra water drawn into your bowels is expelled along with stool. The process continues until your bowel has cleared the excess stool and fluid stimulated by the magnesium citrate.

Within a day of taking a dose, you should feel back to normal. Contact your healthcare provider if you have any concerns.

What If Magnesium Citrate Does Not Work?

It can be frustrating and concerning if you've taken magnesium citrate for constipation and it doesn't seem to be working. Here's what to consider and what steps to take:

• Give it Enough Time: Remember, magnesium citrate typically takes anywhere from 30 minutes to 6 hours to produce a bowel movement. Make sure you've waited for the maximum time in that window before concluding it hasn't worked.
• Are You Hydrated? Magnesium citrate works by drawing water into your bowels. If you are dehydrated or haven't drunk enough fluids with and after taking the dose (the usual recommendation is a full 8-ounce glass of water with the dose, plus more fluids afterward), it might not be as effective. Try drinking some more water (unless you have fluid restrictions from your doctor).
• Check the Dose and Instructions: Did you take the dose recommended on the package or by your doctor? Ensure you followed any specific instructions, like shaking the bottle well.
• Do NOT Take Another Dose (Without Advice): It's very important not to take another dose of magnesium citrate or any other laxative without first talking to your doctor or pharmacist. Taking too much can lead to dehydration, electrolyte imbalances, magnesium toxicity (especially if you have kidney problems), or severe diarrhea and cramping.

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When to Call a Doctor

This is the most important step if time has passed and nothing has happened. You should contact your doctor or pharmacist if:

• It has been more than 6 hours since you took the recommended dose, and you've had no bowel movement at all.
• You experience severe abdominal pain, cramping, bloating, nausea, or vomiting.
• You experience rectal bleeding. The package insert specifically warns to "Stop use and ask a doctor if you have rectal bleeding or failure to have a bowel movement after use." These could be signs of a serious condition.
• Magnesium citrate (or other laxatives) frequently doesn't work for you. This could indicate a more significant underlying issue causing the constipation, such as a blockage or another medical condition and warrants a discussion with your healthcare provider.

This is not all the information you need to know about magnesium citrate for safe and effective use and does not take the place of your doctor’s directions. Review the full product information and discuss this information and any questions you have with your doctor or other health care provider.

Read this next: Magnesium 101: Benefits, types, foods & dosage guide

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Drug information

• Magnesium Citrate Information for Consumers
• Magnesium Citrate prescribing info & package insert (for Health Professionals)
• Side Effects of Magnesium Citrate (detailed)
• Magnesium Citrate user reviews (501)

Related support groups

• Magnesium Citrate (45 questions, 76 members)
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