Drinking Magnesium Citrate for Colonoscopy Prep? Here’s How to Do It

Most people don’t look forward to the bowel prep for a colonoscopy. In fact, many will say that it’s worse than the procedure itself. Magnesium citrate — one of the most common ways to bowel prep — doesn’t taste great. And it can be even more unpleasant when it starts to take effect. But there are ways to make the prep process go down a little easier. So we’ll review the best way to take magnesium citrate before a colonoscopy. 

Why do you need to drink magnesium citrate before a colonoscopy?

A colonoscopy allows your doctor to look at the inside of your intestines. Preparing for a colonoscopy requires cleaning out your bowels so that your healthcare provider can see the inside of your intestines more clearly. The goal of preparing for the procedure is to completely clear your bowels of any waste. Magnesium citrate helps to do that.

Magnesium citrate is a kind of laxative that pulls water into your intestine. This not only softens your stool, but it also increases how often you poop. This means that when you drink a large amount of magnesium citrate — like before a colonoscopy — you’ll be using the bathroom quite frequently. 

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But before you even prepare for the aftereffects, there are some ways to make the initial drink a little more palatable.

How can you make magnesium citrate taste better?

Magnesium citrate has a bitter taste, which can make it unappealing. And you may think it’s impossible to drink colonoscopy prep without throwing up. But there are a few tricks that might help.

To drink magnesium citrate without gagging, try:

• Chilling the solution in your refrigerator before drinking it

• Mixing it with lemon or citrus-flavored drinks like 7 Up or Sprite

• Drinking something that you like after you drink the magnesium citrate, like coconut water or black coffee 

• Drinking with a straw to bypass your tongue, which may help lessen the taste

• Sucking on mints or menthol lozenges in between sips

• Asking your healthcare provider for anti-nausea medicine that you can take during your prep

And don’t rush or chug the fluid. Instead, take your time drinking it. If you give yourself enough time to drink it slowly while still allowing it to work, it can help you keep it down.

How long does it take magnesium citrate to work?  

Magnesium citrate has been shown to work 2 to 4 hours after taking it. By the afternoon or evening of the day before your procedure, you’ll start your preparation process. This is when you’ll first take magnesium citrate. 

If you plan to drink the solution slowly, you may want to start drinking it earlier in the afternoon instead of the evening. Both timelines should get you ready in time for your procedure the next day. 

In some cases, people with certain medical conditions like chronic constipation may require an extra day of prep. But your healthcare provider can help you determine if you may need a longer prep time. 

You’ll also be asked to drink another bottle of magnesium citrate about 5 to 6 hours before your colonoscopy, on the day of your procedure. This means that if your procedure is scheduled for very early in the morning, you may have to wake up in the middle of the night. 

You’ll want to stop drinking liquids completely around 3 to 4 hours ahead of your procedure, so keep this in mind when you’re planning.

Do you need to drink the whole bottle of magnesium citrate?

Yes, drink the whole bottle of magnesium citrate if you can. If you’re having trouble finishing it, call your healthcare provider’s office to let them know. In this case, they may want to reschedule your procedure. 

What else should you do to prepare for a colonoscopy?

There are other things you can do to prepare for a colonoscopy to make it less stressful. To help prepare, try taking the following steps.

3 to 7 days before the procedure 

In the week before your colonoscopy, avoid foods that tend to take a longer time to move through the digestive tract. These include foods that are high in fiber like:

• Raw vegetables and fruits (especially corn)

• Nuts and seeds

• Grains, including oatmeal, brown rice, and wheat bread

In addition to modifying your diet, talk with your healthcare provider about medications that you’re taking. You may need to stop taking certain medications for a period of time before and after your procedure.

And before you start drinking the magnesium citrate, stock up on moist wipes and diaper cream if you can. These help avoid irritation from wiping after frequent bowel movements.

1 day before the procedure

The day before your colonoscopy, you’ll start a clear liquid diet. Foods and drinks that are allowed include:

• Black tea or coffee (no cream or milk added)

• Water

• Ginger ale

• Chicken broth

• Apple juice

• Light-colored popsicles

• Gelatin (Jell-O)

Be sure to avoid red, orange, and purple foods and drinks at this point because those can be mistaken for blood. 

Plan for an evening at home the day before your procedure because this is generally when you start your prep and will want to be close to a bathroom.

And finally, arrange for transportation to and from your procedure. You’ll need a ride home after receiving anesthesia for the procedure. But having someone drop you off will be better as well, so you can stay as relaxed as possible.

Day of the procedure

The morning of your colonoscopy is when you’ll finish your prep. Avoid eating and drinking 2 to 4 hours ahead of your scheduled procedure. Confirm the actual time frame with your doctor’s office, since some places require a longer window than others. 

Once it’s over, you may wonder if you’ll continue frequently going to the bathroom. For most people, bowel movements return to normal in about 2 to 3 days after their colonoscopy. And by the following day, you should be able to resume your normal activities.

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Written by:

Cherilyn Davis, MD

Cherilyn Davis, MD, is a board-certified pediatrician in New York City. She has held local and national roles at the American Medical Women’s Association including board member of the physician division and physician chair of social media.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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