How to Prepare for Your Colonoscopy: A Comprehensive Patient Guide

• Colonoscopy is an important screening tool for colorectal cancer, generally recommended for individuals aged 45 and above. Proper preparation is essential to ensure a thorough and accurate examination.
• Colonoscopy preparation can be completed in two ways: home preparation or hospital-based preparation. Both approaches are designed to ensure a clean bowel, which is critical for a successful examination.
• At Samitivej, colonoscopy is performed using AI-assisted technology combined with Narrow Band Imaging (NBI), enabling detailed visualization and supporting accurate detection for high-quality screening results.

Colonoscopy is an effective screening tool for colorectal cancer. It allows doctors to examine the inside of the colon (large intestine) to detect abnormalities such as polyps—small growths that may develop into cancer if left untreated. If polyps are found, they can often be removed during the procedure and sent for further examination. This process is called a polypectomy and is painless, as specialized instruments such as an electric snare are used, with any minor bleeding treated immediately.

Current international guidelines generally recommend undergoing a screening colonoscopy starting at age 45. However, individuals with additional risk factors, such as a family history of colorectal cancer, certain medical conditions, or lifestyle factors, may be advised to begin screening earlier. Consulting a physician is essential to determine the most appropriate screening schedule for each individual.

Proper colonoscopy preparation is crucial for a successful and thorough examination. To ensure a clear view of the colon lining, the bowel must be completely clear. Preparation methods can generally be divided into two approaches: home preparation and hospital-based preparation, both designed to help achieve the best possible screening results.

Before beginning colonoscopy preparation, a consultation with a physician is needed. During this consultation, the doctor will review the patient’s medical history, current medications, and any existing health conditions, as well as address any concerns or questions about the procedure.

Sedation options will also be discussed at this stage. In most cases, patients are given mild to moderate sedation to help minimize discomfort and anxiety during the examination. This allows the procedure to be performed smoothly while ensuring patient comfort and safety.

A few days before the colonoscopy, patients are advised to adjust their diet to help ensure a clean and clear view of the colon.

Foods to avoid a few days before colonoscopy
Avoid high-fiber foods, as they can leave residue in the bowel, including:

• Fruits
• Vegetables
• Multigrain products
• Whole wheat bread
• Popcorn
• Mushrooms

Recommended low-residue foods before the examination
Choose a low-residue diet, such as:

• Porridge
• Clear or light soup
• Fish
• Chicken
• Tofu
• Eggs
• Soft white bread
• Plain biscuits

Following these dietary recommendations helps improve the effectiveness and accuracy of the colonoscopy.

One Day Before the Examination

1. Throughout the day before the examination, please consume only a full liquid diet, such as: soup or clear broth, congee, non-red gelatin desserts, clear carbonated drinks or sports drinks, and avoid solid foods.
2. Prepare the oral laxative Solution:
   • Pour all solution powder into a container with a capacity of at least 2 liters.
   • Add water to make a total volume of 2 liters and shake well until the powder is completely dissolved.
   • Once prepared, the solution may be stored in the refrigerator for up to 48 hours.
3. Your last meal should be taken at 4:00 PM, approximately 2 hours before starting the oral laxative.
4. Take 2 tablets of prescribed anti-nausea medication at 5:00 PM, as instructed, to help reduce nausea and bloating.
5. Drinking oral laxative:
   • Begin drinking oral laxative at 6:00 PM.
   • Drink 1 glass (approximately 8 ounces) every 10–15 minutes over a period of 2 hours.

Important fasting instructions before the examination:

• If you experience nausea, fullness, or bloating, you may slow down by increasing the time between each glass.
• It is important to finish the entire solution to ensure a clear view of the colon for accurate examination results.
• Bowel movements typically begin 1–3 hours after starting the solution.
• After finishing oral laxative and once bowel movements begin, you may drink water as needed. However, refrain from eating or drinking after midnight or within 6 hours before your scheduled examination.

The Examination Day

• Fasting Reminder: Please refrain from eating or drinking after midnight or within 6 hours before your scheduled examination time, as instructed by your physician.
• Arrival Time: Please arrive at the hospital at least 30 minutes before your scheduled examination time to allow sufficient time for preparation.

One Day Before the Examination

1. Throughout the day before the examination, please consume only a full liquid diet, such as: soup or clear broth, congee, non-red gelatin desserts, clear carbonated drinks or sports drinks, and avoid solid foods.
2. Please refrain from eating or drinking after midnight, as instructed by your physician.

The Examination Day

1. Arrival Time: Depending on your scheduled examination time, you will be asked to arrive at the hospital at a specific time in advance (most commonly in the morning) to allow for preparation and monitoring.
2. Bowel Preparation at the Hospital: The hospital will prepare the oral laxative solution and guide you through the process. You will be instructed to drink the solution over a period of 2 hours, at a rate of 1 glass (approximately 8 ounces) every 10–15 minutes, under medical supervision.
3. After Bowel Cleansing: Once bowel movements are adequately cleared, the medical team will prepare you for the colonoscopy procedure.

Most patients receive sedation and pain-relief medication to help them stay comfortable during the procedure. The colon is gently inflated with air so the doctor can clearly see the lining of the intestine.

Depending on age and overall health, some patients may receive lighter sedation. For this reason, it is important to discuss your medical history, current medications, and any concerns with your doctor beforehand.

A colonoscopy typically takes about 30–60 minutes, based on commonly referenced clinical guidance. The duration may be longer if polyps are found or additional treatment is required to ensure a careful and complete examination.

After the procedure, patients will remain in a recovery room for at least 2 hours for close observation and to allow the effects of sedation (if used) to wear off. It is recommended that patients arrange for a companion to accompany them home. If this is not possible, the hospital can assist in arranging transportation at the patient’s own expense.

For the first 24 hours after the procedure, patients are advised to refrain from:

• Driving or operating machinery
• Engaging in hazardous activities
• Consuming alcohol
• Returning to work
• Making important personal, financial, or legal decisions

At Samitivej, the Colorectal Center provides care for the prevention, detection, and treatment of colorectal diseases. Our team of experienced gastroenterologists and colorectal specialists focuses on careful evaluation, precise technique, and patient safety at every stage of care.

Our doctors undergo structured training and continuous professional development, supported by an ongoing academic collaboration Sano Hospital in Japan, a recognized leader in advanced gastrointestinal endoscopy. This partnership emphasizes skills refinement, knowledge exchange, and adherence to internationally accepted best practices.

To support clinical assessment, our specialists use enhanced imaging technologies such as Narrow Band Imaging (NBI) and AI-assisted visualization. These tools assist the examination, while the thoroughness and quality of the procedure are guided primarily by the physician’s expertise, technique, and clinical judgment.

In addition, our practice aligns with internationally recognized quality indicators established by the American Society for Gastrointestinal Endoscopy (ASGE), reflecting our commitment to thorough, reliable, and well-standardized colonoscopy. Based on internal data from 27,687 procedures performed between 2017 and 2026:

• Complete examination rate (cecal intubation rate): 100%
• (ASGE benchmark ≥95%)
• Adenoma detection rate (ADR): 40% overall and 45% in patients aged ≥50
• (ASGE benchmark ≥35%)
• Post-polypectomy bleeding rate: 0.1%
• (ASGE benchmark ≤1%)

These results, along with other quality indicators, are monitored as part of our ongoing effort to measure performance, maintain patient safety, and support continuous improvement in care.

Early detection plays a vital role in preventing colorectal cancer. With proper preparation, experienced specialists, and advanced technology, colonoscopy can be performed safely, comfortably, and effectively. If you have concerns or planning for screening, our team is here to support you every step of the way.