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Patient Information

Diabetes and having an endoscopy with bowel preparation

https://kingstonhospital.nhs.uk/information/diabetes-and-having-an-endoscopy-with-bowel-preparation

This leaflet is for anyone with diabetes (of any type) who is due to have an endoscopy that requires them to have bowel preparation (see box, right).

This covers:

  • colonoscopy
  • sigmoidoscopy
  • gastroscopy and colonoscopy
  • gastroscopy and sigmoidoscopy.
Bowel preparation (or ‘Bowel prep’) means completely emptying the bowel before a procedure. This is done by taking medicines to make you go to the toilet, and by cutting down and then stopping food a few days before.

Here we cover how to alter your insulin or other diabetes medication around the time of your appointment to control your blood sugar safely.

Follow what applies to you:

If you control your diabetes with diet alone, you do not need to do anything apart from the bowel preparation instructions you have been sent.

Remember:

Illustration on mobile phone

Tell the endoscopy team that you have diabetes. We can then give you an appointment as close to the start of the morning or afternoon as possible. This is to reduce any disruption to your usual insulin or medication regimen.

Photo of glucose tablets

On the day before and the day of the procedure carry glucose tablets in case of low blood sugar levels. If your blood sugar levels drop (less than 4 mmol/l), see the hypoglycaemia instructions at the end of this document.

If you have had a ‘hypo’ and taken glucose, tell the nurses when you arrive.

Photo of finger prick to test blood sugar

If you usually check your blood sugar levels yourself, you should continue to do so, particularly before taking insulin. If you do not usually check them, we will do so when you arrive.

Instructions for those on insulin

What time is your appointment?

Morning appointment (before 12.30)

What insulin are you on?

Insulin twice a day (before breakfast and before evening meal)

Novomix 30
Humalog Mix25 or Mix50
Humulin M3

Short-acting insulin before meals (3 times a day)


Novorapid
Humalog
Apidra

Background insulin in the morning and/or evening

Insulatard
Humulin I

Background insulin in the morning and/or evening

Levemir (detemir)
Lantus (glargine) Toujeo
Tresiba

Day before

Drink clear fluids and sugary drinks only.


Take half your usual insulin dose.

Because you cannot eat solid food, replace your carbs with sugary drinks, juices or jellies, and monitor your blood sugar.

Drink clear fluids and sugary drinks only.


Take half your dose for each injection.

Or
if no carbohydrate intake, no insulin needed

Or
if carb counting, adjust your dose accordingly.

Drink clear fluids and sugary drinks only.

Reduce each dose by one-fifth (reduce it by 20%) when taking morning and/or evening dose.

To work out your reduced dose, times your usual dose by 0.8 .

Drink clear fluids and sugary drinks only

Take your usual insulin as normal.

Day of the appointment

You can have clear fluids until 6am.

Do not take morning insulin.

Take half your usual insulin dose when you can eat and drink.

Take your usual insulin dose with evening meal.

You can have clear fluids until 6am.

Do not take your morning insulin.

Bring your morning insulin dose with you and take it when you can eat and drink right after the test.

You can have clear fluids until 6am.

Reduce your morning dose by a one-fifth (20%),

Have your usual evening dose.

You can have clear fluids until 6am.

Have your morning dose and evening dose as usual.

Afternoon appointment (after 12.30)

What insulin are you on?

Insulin twice a day (before breakfast and before evening meal)

Novomix 30
Humalog Mix25 or Mix50
Humulin M3

Short-acting insulin before meals (3 times a day)


Novorapid
Humalog
Apidra

Background insulin in the morning and/or evening

Insulatard
Humulin I

Background insulin in the morning and/or evening

Levemir (detemir)
Lantus (glargine) Toujeo
Tresiba

Day before

Drink clear fluids and sugary drinks only.

Take half your usual insulin dose.

Because you cannot eat solid food, replace your carbs with sugary drinks, juices or jellies, and monitor your blood sugar.

Drink clear fluids and sugary drinks only.

Take half your dose for each injection.

Or
if no carbohydrate intake, no insulin needed

Or
if carb counting, adjust your dose accordingly.

Drink clear fluids and sugary drinks only.

Reduce each dose by one-fifth (reduce it by 20%) for morning and/or evening dose.

To work out your reduced dose, times your usual dose by 0.8 .

Drink clear fluids and sugary drinks only

Take your usual insulin as normal.

Day of the appointment

You can have clear fluids until 11am.

Take half the dose (reduce it by 50%) in the morning.

Bring your dose with you to have when eating and drinking.

You can have clear fluids until 11am.

Take half your morning dose.

Do not take your lunchtime dose, but bring it with you and take it when you can eat and drink.

If carb counting, adjust your dose accordingly.

You can have clear fluids until 11am.

Take half your morning dose (reduce it by 50%) with clear fluids and sugary drinks.

To work out your reduced dose, times your usual dose by 0.5 .

Have your usual evening dose.

You can have clear fluids until 11am.

Take your usual insulin as normal.

Instructions for those on medications other than insulin

What time is your appointment?

Morning appointment (before 12.30)

What diabetes medication are you on?

Tablets

metformin
sitagliptin
saxagliptin
linagliptin
pioglitazone
dapagliflozin
empagliflozin

Tablets

gliclazide
glimepiride
tolbutamide
repaglinide
glibenclamide

Tablets

exenatide
liraglutide (Saxenda, Victoza)
dulaglutide (Trulicity)
Bydureon
semaglutide (Ozempic)
Xultophy
lixisenatide

Day before

Take your doses as normal.

Note: for dapagliflozin and empagliflozin, drink plenty of fluids.

Do not take your evening dose.

As you cannot eat solid food, monitor your blood sugar.

Take your dose as normal.

Day of the appointment

Do not take your morning dose, but bring them to your appointment.

When you can eat and drink after the procedure, take your morning dose.

Do not take your morning dose, but bring them with you.

When you can eat and drink after the procedure, take your morning dose.

Take your dose as normal.

Afternoon appointment (after 12.30)

What diabetes medication are you on?

Tablets

metformin
sitagliptin
saxagliptin
linagliptin
pioglitazone
dapagliflozin
empagliflozin

Tablets

gliclazide
glimepiride
tolbutamide
repaglinide
glibenclamide

Tablets

exenatide
liraglutide (Saxenda, Victoza)
dulaglutide (Trulicity)
Bydureon
semaglutide (Ozempic)
Xultophy
lixisenatide

Day before

Take your lunch time and evening dose.

Note: for dapagliflozin and empagliflozin, drink plenty of fluids.

As you cannot eat solid food, replace your carbs with sugary drinks, juices, or jellies.

Take your lunch time and evening dose.

As you cannot eat solid food, replace your carbs with sugary drinks, juices, or jellies.

Take your dose as normal.

Day of the appointment

Do not take your morning dose, but bring them to your appointment.

When you can eat and drink after the procedure, take your morning dose.

Do not take your morning dose, but bring them with you.

When you can eat and drink after the procedure, take your morning dose.

Take your dose as normal.

General advice

For advice about insulin dose adjustments, contact the diabetes nurse team on 020 8934 6370.

Avoiding low blood sugars

  • Check your blood glucose regularly.
    If it drops below 4 mmol/l, have approximately 20g carbohydrate (see Box 1 ) until your blood glucose is back above 5. You can do this for up to 4 hours before your appointment.
  • To avoid the risk of low blood sugars, you can have sips of water and/or sips containing carbohydrates until 2 hours before your appointment. 
    See Box 1 and Box 3 for examples.
Box 1
For approx. 20g carbohydrates

 200ml (13 tablespoons) of non-diet cola 
OR
  4 teaspoons of sugar in 100ml of water
OR
 200ml clear apple/grape juice
OR
 220ml Lucozade
OR
 5 or 6 glucose tablets

Hypoglycaemia

  • If you have a hypo (hypoglycaemia) during the 4 hours before your appointment, follow the advice in Box 2.
    Tell the endoscopy department if this happens.
  • If your blood glucose does drop below 4 and/or you take glucose, let the endoscopy nurses know when you arrive, or call us if you think that it will be difficult to come for your appointment. 
Box 2
Hypo treatment

Step 1
Take 15 to 20g rapid-acting glucose:
5 to 6 dextrose/Lucozade sweets
OR
5 to 6 Glucotabs
OR
150ml to 200ml fruit juice or non-diet cola
OR
one 60ml bottle Glucojuice (Lift)

Step 2
Test glucose after 10 minutes
Repeat step 1 if still below 4.0mmol/L

For type 1 diabetes

  • Whilst on clear fluids only, aim for 100g to 150g of carbs (carbohydrate) spread over 7 portions during the day.
    See Box 3 for fluids that do and do not contain carbohydrates.
  • Have half your normal amount of quick-acting insulin at your normal times.
  • Monitor your blood sugars at least every 4 hours during the day.
  • If you have a hypo, follow the advice in Box 2.

For type 2 diabetes treated with 2 injections a day

  • Whilst on clear fluids only, aim for 100g to 150g of carbs (carbohydrate) spread over 7 portions during the day.
    See Box 3 for fluids that do and do not contain carbohydrates.
  • Reduce your normal insulin dose by one-third i.e., divide by 3. 
  • Monitor blood sugars every 4 hours. 

Box 3
Fluids containing NO carbohydrate:
sugar-free squash
diet fizzy drinks  
Bovril, Oxo or Marmite  
black Tea and coffee     
sugar-free jelly  
water.

Fluids containing carbohydrate:
non-diet fizzy drinks have 35g carbs per 330ml can
125g pot ready-made jelly (not sugar-free) has 16g carbs
100ml clear pure apple juice has 11g carbs.

Diabetes and having an endoscopy with bowel preparation - Kingston Hospital Download PDF


Contacts

Endoscopy nurses helpline 020 8934 6614 (2pm to 4pm only)
Diabetes nurses 020 8934 6370

Translate Please speak to a member of staff before or during your visit to the hospital if you require translation.
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For information accessibility please visit Kingston Hospital AccessAble www.accessable.co.uk/kingston-hospital-nhs-foundation-trust
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Accessibility

Please contact the Patient Experience Team on 020 893 3850 if you need this information in a different format.
For detailed information on accessibility at Kingston Hospital visit Kingston Hospital AccessAble (https://www.accessable.co.uk/kingston-hospital-nhs-foundation-trust).


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