Procedure prep
Fasting Before a Colonoscopy
A colonoscopy is different from most procedures — you need bowel prep AND fasting. Get both right or it may be rescheduled.
Medically reviewed by
Dr. Saurabh Shukla, MBBS, DNB Anesthesiology
· Last updated June 2026
Fasting for this procedure
Follow your bowel-prep instructions exactly — usually a clear-liquid diet the day before plus a laxative prep. After that, standard sedation fasting applies: stop clear liquids about 2 hours before your hospital arrival time, and no solid food once your prep diet begins. Your prep instructions override general rules. Use the colonoscopy prep timing calculator to map your exact dose times to your appointment.
→ Get your exact fasting times with the calculator
Medicines to check
- Blood thinners — biopsies or polyp removal may be planned, so timing matters. See medications to stop.
- Diabetes medicines and insulin — a clear-liquid prep day changes your sugar; ask for a plan. See diabetes tablets.
- Iron tablets are usually stopped a few days before (they darken the bowel lining).
- Blood pressure medicines — confirm which to take with a sip of water.
When this surgery may be delayed
- Your bowel prep wasn't completed or your bowel isn't clear
- Fever, vomiting, or a new infection
- You ate solid food when you should have been on clear liquids
Reports & documents to carry
- Photo ID and insurance card
- List of all medicines and doses
- Your bowel-prep instructions
- A responsible adult to drive you home (sedation is used)
What to ask your anesthesia team
- Exactly when do I start the clear-liquid diet and the prep?
- Which medicines do I take, hold, or stop?
- When do I stop clear liquids before arrival?
- Will I have sedation, and who can drive me home?
Your prep checklist
Tick things off as you sort them — saved on this device only, nothing is sent anywhere.
A general guide — your hospital's own instructions always come first.
Frequently asked questions
Can I drink water before a colonoscopy?
Yes — clear liquids are usually allowed up to about 2 hours before your hospital arrival time, on top of finishing your bowel prep. Follow your prep instructions exactly.
What can I eat the day before a colonoscopy?
Usually only clear liquids the day before — water, clear broth, apple juice, clear sports drinks — and no solid food. Avoid red or purple drinks. Follow the specific diet your team gives you.