Screening colonoscopy: prep, the day, risks and results

The days before: diet and medicines

Low-fiber food for a few days: you may be asked to avoid foods such as whole grains, nuts and seeds, beans, and raw fruits and vegetables. (ACS, 2026) (NIDDK, 2023)
Clear liquids before the test: usually starting the day before, up to a time your team sets. Clear liquids have no pulp, solids or cream: water, broth, plain coffee or tea, pulp-free apple or white grape juice, light-colored sports drinks and gelatin. You may be told to avoid red and purple ones. (NIDDK, 2023) (ACS, 2026)
Where guidance varies: the US Multi-Society Task Force (2025), as summarized in a 2026 review, says the early and midday meals the day before should be low-residue or low-fiber foods, or full liquids, when the prep is split, for outpatients at low risk of a poor prep. Follow the instructions you are given. (APT review, 2026)
Medicines: tell your doctor about everything you take, including vitamins, herbs and supplements. You might be asked to pause blood thinners, including aspirin, or iron, or to adjust diabetes medicines. Do not change any medicine unless your doctor tells you to. (ACS, 2026)
A ride home: plan it before the day; you cannot drive after sedation. (NIDDK, 2023) (ACS, 2026)

The bowel prep

The colon has to be empty so the doctor can see the lining. Preps can be liquids, pills, enemas or a mix, and your provider prescribes one. Many involve drinking a liquid laxative, often split between the night before and the morning of the test, and they cause frequent diarrhea, so stay near a bathroom. (NIDDK, 2023) (ACS, 2026) Read the instructions a few days ahead, since you may need to buy supplies. (ACS, 2026)

The Task Force recommends a split-dose prep for everyone, with the second part taken 4 to 6 hours before the colonoscopy, and says no one prep is better than another for most outpatients at low risk of a poor prep. (APT review, 2026) It is important to finish the prep; call your health care team if side effects stop you. (NIDDK, 2023)

On the day

It is usually an outpatient procedure. You lie on your side, and your blood pressure, heart rate and breathing are watched. (ACS, 2026)
Most people get sedative and pain medicines through an IV; some are fully asleep under anesthesia, and having no sedation is uncommon. You may feel pressure or mild cramping. (ACS, 2026)
The doctor passes a thin, flexible scope with a camera through the whole colon, using air to see clearly, and removes polyps or takes samples if needed. You do not feel polyp removal or a biopsy. (ACS, 2026) (NIDDK, 2023)
The test usually takes about 30 minutes, longer if polyps are removed. (ACS, 2026)

Afterward

You are watched for about 30 to 60 minutes while the sedation wears off, and may not remember the test. Bloating, gas or cramps from the air are common for a while. (NIDDK, 2023) (ACS, 2026)
Someone has to drive you home and stay with you until the sedation wears off. (ACS, 2026) Most people recover fully and eat normally by the next day. (NIDDK, 2023)
Light bleeding from the anus for a day or 2 is normal if polyps were removed or a biopsy was done. (NIDDK, 2023) (ACS, 2026)
Get care right away for severe belly pain, fever, bloody bowel movements that do not get better, bleeding that does not stop, dizziness or weakness. (NIDDK, 2023)

Risks, with numbers

Bleeding and perforation (a tear in the colon wall) are the most common serious complications. (NIDDK, 2023) In the evidence the USPSTF reviewed, screening colonoscopy led to about 14.6 major bleeding events and 3.1 perforations per 10,000 procedures. Rates were higher for colonoscopies done after a positive stool test, probably because more polyps are removed and more biopsies taken. (USPSTF, 2021) Most bleeding and perforations happen in older people or when polyps are removed; bleeding can show up up to 2 weeks later, and a perforation may need surgery. (NIDDK, 2023) Sedation can cause heart and breathing problems such as an irregular heartbeat. (NCI, 2025)

Results and your next date

The doctor may share what was seen once the sedation wears off. If polyps or samples were taken, a pathologist examines them and results usually take a few days or longer; you will get a call or an appointment to go over them. (NIDDK, 2023) (ACS, 2026)

Normal: for adults at average risk, the USPSTF lists colonoscopy every 10 years. (USPSTF, 2021)
Polyps removed: the next date depends on their type, size and number, from 6 months to 10 years. See colonoscopy after polyps. (USMSTF, 2020)
Prep not good enough: those intervals assume a good prep and a complete exam. (USMSTF, 2020) The 2026 review says that when the prep is inadequate, current quality guidance calls for a repeat colonoscopy within 12 months. (APT review, 2026) Your doctor tells you your date.

What it costs

Medicare Part B covers a screening colonoscopy once every 120 months, or every 24 months for people at high risk, with nothing to pay for the screening if your provider accepts assignment, including a follow-up colonoscopy after a positive stool or blood test. If a polyp or other tissue is removed, you pay 15% of the Medicare-approved amount for your provider's services, plus a 15% facility coinsurance in a hospital outpatient setting or surgery center. (Medicare.gov) Private plans: see colorectal tests compared.

Questions people ask

How long does a colonoscopy take?

The test itself usually takes about 30 minutes, longer if polyps are removed; the NIDDK says it usually takes less than an hour. You are watched for about 30 to 60 minutes afterward, and an outpatient visit takes a few hours in all. (ACS, 2026) (NIDDK, 2023)

Is a colonoscopy painful?

Many people feel some discomfort, but it is usually not painful. Most people get sedative and pain medicines through an IV; some are fully asleep, and having no sedation is possible but uncommon. (ACS, 2026)

Can I take a taxi home after a colonoscopy?

If you had a sedative, someone needs to drive you home and stay with you until it wears off. The American Cancer Society says a cab or rideshare may not be a good option, and some clinics do not allow it. Talk to your provider if getting home is a problem. (ACS, 2026)

What are the risks of a screening colonoscopy?

Bleeding and a tear (perforation) in the colon wall are the most common serious problems. In the evidence the USPSTF reviewed, they happened in about 15 and 3 of every 10,000 screening colonoscopies. They are more likely when polyps are removed. Sedation can also cause heart or breathing problems. (USPSTF, 2021) (NIDDK, 2023) (NCI, 2025)

When will I get my colonoscopy results?

The doctor may tell you what was seen once the sedation wears off. If polyps or tissue samples were taken, lab results usually come within a few days, sometimes longer, and you need to follow up with your doctor to get them. (NIDDK, 2023) (ACS, 2026)

Screening colonoscopy: what to expect