Preparing for your colonoscopy

Find answers to common questions about colonoscopies.


Beginning at age 45, all adults should have a colon cancer screening and a follow-up screening every ten years after the first one. It's important not to delay. One test can make a big difference for your health. For more information, talk to your doctor. 

Below you can find answers to common questions you may have about preparing for your colonoscopy.

I've taken the first half of my prep, but I haven't had a bowel movement.

For many people, the first half of the bowel prep doesn't lead to bowel movements. Some people don’t even feel an urge to move their bowels. In almost every case, the prep will eventually work as planned. 

You should keep on taking the second half of the bowel prep as it says in the directions. If your stool is not starting to clear three hours after you take the morning dose (amount of medicine) of laxative, call our office or the on-call doctor at 1-425-339-5421.

I'm nauseous and vomiting. What do I do?

The first thing to do is stop taking the bowel prep and take a break. That might mean 30 minutes or even an hour before you drink any more. After your nausea has decreased or stopped, you can start the bowel prep again, but you should drink it at a slower rate.

Sometimes, drinking too much, too quickly is too much for your system to handle. Another tip is to make sure the prep is chilled. It helps to refrigerate the liquid prep. Drinking some cold water along with the prep liquid may also help.

If you already have an anti-nausea medication at home and have done well with it in the past, you can try taking a dose.

Examples might include:

  • Ondansetron (Zofran)
  • Promethazine (Phenergan)
  • Prochlorperazine (Compazine)
  • Metoclopramide (Reglan)

If your nausea and vomiting persist, please call us to talk about your symptoms. 

I accidentally took aspirin or iron.

You don't need to cancel if you took aspirin or iron by mistake. It’s fine to take aspirin as needed and it should not cause any problems with the colonoscopy.

If you didn’t stop taking iron for the week leading up to the colonoscopy, there is a small chance that the quality of the bowel preparation may not be good. It’s hard to know if the iron will affect how well your prep will work.

If you have already started the bowel prep, it’s best to keep going with it. If you took one or two doses of iron by mistake, it shouldn't be an issue.


The pharmacy did not have my medications.

If it's during normal business hours (8 a.m. to 5 p.m.), please call our office at 1-425-339-5421. Someone on our team can call the pharmacy for you.

If you're calling outside of our normal business hours, please call our office at 1-425-339-5421. Select the choice to have our on-call doctor paged. The on-call doctor will call the pharmacy for you.


Can I take my anxiety medications?

Yes, if you take medication for anxiety (worrying more than normal) or depression, you can take your medications before coming in for your colonoscopy.

I have diabetes and my blood sugar is low.

We know how important a healthy blood sugar levels is for our patients, especially those with diabetes. It's important to remember that even though we ask you not to eat solid food during the bowel prep process, clear liquids are still allowed.

To help with your blood sugar level, try drinking juice (apple juice or orange juice without pulp) or fruit flavored beverages (lemonade).


I have a headache. Can I take Tylenol®?

Yes. Tylenol (acetaminophen) is allowed, but no more than 4,000 mg (milligrams) should be taken in 24 hours. If you have an allergy to Tylenol, then you should not take it.

Also, if you have liver failure or cirrhosis, you should limit the amount of Tylenol that you take to 2,000 mg in 24 hours.

What can I mix with the MiraLAX® powder?

You can mix your MiraLAX powder with:

  • Water
  • Gatorade
  • Pedialyte®
  • Crystal Light

Don’t mix MiraLAX with carbonated beverages (soda) or alcohol. 

Can I drink all of my prep the night before?

No. We ask patients not to drink all of the prep the night before their colonoscopy, and to finish their dose the next morning.  

Studies have shown that split dose preps (in which laxatives are taken the evening before and the morning of the colonoscopy) produce better cleansing. 

While this can make for an early morning, the most important thing is that you get a good quality exam. A good quality exam will reduce the chance of having to repeat the prep and the colonoscopy or having polyps missed during the exam.

If there is stool residue stuck to the side of your colon, your doctor may not be able to find and remove all polyps and cancer can be missed.

What time do I really need to start my clear liquid diet?

The clear liquid diet (not eating solid food) is aimed at lessening stool production in the body. This allows us to use a small volume of bowel prep and have a better cleansing of the colon.

We ask that you start the clear liquid diet the day before your colonoscopy starting in the morning with your first meal until two hours before your check-in time on the day of your colonoscopy.

Do I need to finish my entire prep?

Even if you're having clear, liquid stool, you still need to finish your prep. Your body produces six to seven liters of fluid a day, even if you're not consuming solid food. This fluid is continuously coating the colon.

Consuming the entire prep helps clean out this fluid and helps improve the quality of your colonoscopy.

What if I'm on antibiotics? 

For most people, being on antibiotics when you have a colonoscopy shouldn't be an issue. It's important to let your doctor know why you're taking antibiotics.

I can't find my prep directions. What do I do?

You have received a letter from The Everett Clinic with your prep directions. These were sent on the day you scheduled your colonoscopy. If you have MyChart, your prep directions can be found there in the "Letters" section.

If you still can't find your prep directions after trying the above suggestions, please call the on-call doctor at 1-425-339-5421.

Can I do a pill prep? 

No. We have seen with tens of thousands of patients over the years that the pill prep doesn't work as well as the standard liquid prep. Pill prep hasn't been studied by doctors and there have been concerns over its safety.

Often pill prep leads to exams that don't work well or that aren't complete. If this happens, you will have to have another colonoscopy. We value your time and that of your family and friends who will bring you to your appointment.

Our goal is to make sure your colonoscopy exam works well. We also don't want you to have to have more colonoscopies that aren't needed.

Can I start my prep earlier or later?

We ask that you start the bowel prep at the time we gave you. But if you do start one or two hours earlier or later than the time given you, that's fine as long as you follow the clear liquid diet for the day.


If I have my menstrual period, can I still have a colonoscopy?

Yes, you can. Menstruation doesn’t cause problems with a colonoscopy.

Can I drink alcohol while completing my prep?

No. Alcohol causes dehydration. Being dehydrated for a colonoscopy could cause serious problems. Also, alcohol can cause problems with the medications given to you during the colonoscopy.

If you have a history of problems with alcohol withdrawal symptoms, be sure to tell us before you schedule your colonoscopy.

Does my prep change because of my size or weight?

No. Laxatives aren't medications that change due to your size or body weight. Your colonoscopy prep and guidelines are based on your bowel habits and the reasons why you're having a colonoscopy.

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The information provided is for general informational purposes only and is not intended to be medical advice or a substitute for professional health care. You should consult an appropriate health care professional for your specific needs.