Abnormal Blood Sugar Tests in Diabetic Patients During Colonoscopy Preparation
Phase: NA
Conditions: Type 2 Diabetes Mellitus, Colonoscopy
Sponsor: Catholic Kwandong University

Study title: Abnormal blood sugar tests in diabetic patients during 
colonoscopy preparation  
 
Primary Investigator: Myong Ki Baeg, MD, PhD 
Investigation site: International St. Mary’s Hospital, Catholic Kwandong University 
 
Last modified: Feb 2, 2018 
 
 
 

 
Objectives 
1. Primary: To discover the incidence of abnormal glucose levels after fasting and bowel preparation 
for colonoscopy in type 2 diabetes subjects.  
2. Secondary  
① Find out the risk factors for abnormal glucose levels 
② Find out if self-treatment is sufficient to treat hypoglycemia which occurs during fasting and 
bowel preparation.              
Background 
Diabetes is rapidly increasing, with about 11% (5.5 million) of the Korean population expected to be 
diabetic in 2030. Diabetes is a known risk factor for colorectal cancer and diabetes patients are 
recommended to undergo routine colonoscopic surveillance. Colonoscopy requires fasting and bowel 
preparation, however, their effects on glucose levels have not been investigated.  
Subjects normally undergo 14-20 hours of fasting before colonoscopy. In diabetes patients, 14-17 
hours of fasting reduces plasma glucose by 20-40%, which increases the risk of hypoglycemia. 
Furthermore, subjects are instructed to forgo taking antidiabetic medications during fasting, which 
may induce hyperglycemic crisis or abnormal glucose levels due to Dawn phenomenon or Somogyi 
effect. Dehydration during bowel preparation may also increase the risk of abnormal glucose levels. In 
diabetic patients, autonomic dysfunction may reduce recognition of hypoglycemic symptoms, 
increasing risk of catastrophic events.  
In diabetic patients who underwent ophthalmologic procedures after 8 hours of fasting, hypoglycemia 
has been reported in 3% and hyperglycemia in 2.4%. One study which investigated abnormal glucose 
responses in diabetes patients who underwent colonoscopy found a hypoglycemic rate of 20%. 
Therefore, we aim to investigate the occurrence of abnormal blood glucose levels in diabetes patients 
during colonoscopy preparation.  
 

Subjects 
1. Inclusion criteria: Type 2 diabetes subjects between the ages of 20-75 who have colonoscopy 
performed at the endoscopy center of International St. Mary’s Hospital.  
2. Exclusion criteria 
① Type I diabetes patients 
② Those who have not completed colonoscopy preparation 
③ Those who have not met the fasting requirements 
④ Patients with known ongoing infection 
⑤ Patients with known cancer, undergoing current treatment 
 
Subject numbers 
The incidence of abnormal glucose levels is expected to be between 5 to 10%. 50 positive subjects 
are required for multivariable analysis, therefore 1000 subjects should be included in this study.  
 
Study design 
1. Colonoscopy preparation 
① Subjects will be instructed to fast from 6pm of the day before colonoscopy. 
② Subjects will be instructed to abstain from diabetes medication while the subjects fast. 
③ Subjects who are scheduled to undergo colonoscopy in the morning will take colonoscopy 
preparation medication (2L (liter) of polyethylene glycol with ascorbic acid) in a split dose (i.e. 
1L from 8-10 pm of the day before colonoscopy and 1L 4-6 hours before colonoscopy). 
Those who will undergo colonoscopy in the afternoon will take 2L of the preparation 
medication 6 hours before colonoscopy. 

④ Subjects will be instructed to take the preparation medication at rate of 250 mL every 10 to 
15 minutes. 
2. Confirmation of diabetes 
① Diabetes history will be rechecked by a trained nurse who is blind to the study at the 
preparation room of the endoscopy center.  
② Subjects will fill out a questionnaire and have their plasma glucose checked while awaiting 
colonoscopy.  
3. Treatment of abnormal glucose levels 
① Hypoglycemic patients with a glucose level < 70mg/dL will be given 5% dextrose water.  
② Hyperglycemic patients with a glucose level > 250mg/dL will be given normal saline.  
③ Treated subjects with be discharged after confirmation of glucose level restoration to 
normal values.  
 
Study variables 
1. Age, gender 
2. Amount and total time of colonoscopy preparation. Total fasting time. Time from last antidiabetic 
medication taken to colonoscopy.  
3. Diabetes history (years), Diabetes treatment method (exercise/diet, oral medication, methods 
including insulin), other injected agents, previous history of hypo/hyperglycemia, hypoglycemia 
awareness 
4. Plasma glucose level before colonoscopy 
 
Statistical Analysis 

Primary endpoint: Percentage of study subjects with hypo or hyperglycemia 
Secondary endpoint 
① Risk factors of hypo/hyperglycemia 
② Effect of hypoglycemia self-treatment 
Verify the risk factors using T test the X2 test.  
Identify the odds ratios of risk factors by univariable and multivariable analysis.  
 
References 
Mary Ann Vann, Perioperative management of ambulatory surgical patients with diabetes mellitus, 
Current Opinion in Anaesthesiology, 2009; 22: 718-724 
Kollarits et al, Perioperative treatment of patients with diabetes having eye surgery with local 
anesthesia in an ambulatory facility, Ophthalmic Surgery Lasers Imaging, 2004; 35: 185-188 
Joshi et al, Society for Ambulatory Anesthesia Consensus Statement on Perioperative Blood 
Glucose Management in Diabetic Patients Undergoing Ambulatory Surgery, Anesthesia Analgesia, 
2010’ 111: 1378-1387 
Yao et al, Enteral nutrition before bowel preparation improves the safety of colonoscopy in the 
elderly, The Turkish Journal of Gastroenterology, 2013; 24: 400-405