In bowel endoscopy and contrast medium examinations, a thorough bowel cleansing is required. Usually, for the preceding 1–2 days, only liquid nutrition and bowel-clearing preparations can be consumed. The unit performing the procedure provides written instructions for preparing for the examination, the preceding lightened diet, and bowel cleansing. Insulin doses may need to be reduced, but basal insulin, or long-acting insulin, must not be stopped completely.
It is advisable for those on insulin therapy to monitor their blood sugar with a glucose sensor or finger-prick measurements every 2–4 hours during a liquid fast.
Diabetes managed with diet or tablets
In diet-controlled diabetes, the cleansing usually does not pose problems. In tablet therapy, depending on the medication used, blood sugar can drop too low during a liquid fast. It is advisable to arrange in advance with the doctor treating the diabetes or the doctor conducting the examination for a possible reduction or pause in tablet medication during the cleansing.
Diabetes managed with insulin
A person using insulin should arrange in advance with their nurse or doctor for a possible reduction of insulin. The fluid consumed during a liquid fast must also contain carbohydrates.
The dosage of basal insulin may need to be reduced somewhat, for example by 10-20%. Those on multiple daily injections may administer rapid-acting insulin only as necessary on the day of cleansing, based on blood sugar correction doses. It is not advisable to reduce the dose of very long-acting basal insulins, such as glargine 300 units/ml or degludec insulin, especially on the morning of the examination, as the impact of the change on blood sugar levels will only become apparent after a delay.
Examination day
If the blood sugar is below 4 mmol/l or if you are not allowed to eat for several hours after the examination, a cannula is inserted into a vein, through which sugar-containing fluid is administered directly into the bloodstream.