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Advice for diabetic patients before surgery if fasting
It’s important to keep taking insulin before surgery. However, your insulin dose or non-insulin medication might need to be adjusted before your procedure IF FASTING. Please refer to the charts below for guidance:
If you have any trouble understanding these instructions, please talk to a member of the pre-operative assessment unit. Tel: 01 634 3687
Non-insulin diabetic medication.
| Drug Class | Drugs in class | Day before procedure | Day of procedure | ||
|---|---|---|---|---|---|
| Morning Procedure | Afternoon Procedure | ||||
| Acarbose | Continue | Omit morning dose if nil by mouth | Take morning dose if eating | ||
| DDP IV inhibitors | Alogliptin Linaglitpin Saxagliptin Sitagliptin Vildagliptin |
Continue | Continue | Continue | |
| GLP-1 receptor analogues | Dulaglutide Exenatide (inc. MR preparation) Liraglutide Lixisenatide |
Continue | Continue | Continue | |
| Meglitinides | Nateglinide Repaglinide |
Continue | Omit morning dose if nil by mouth | Take morning dose if eating | |
| Metformin* (inc. MR preparations) | ONCE or TWICE daily | Continue | Continue | Continue | |
| THREE times daily | Continue | Omit lunchtime dose | Omit lunchtime dose | ||
| Pioglitazone | Continue | Continue | Continue | ||
| SGLT-2 inhibitors | Canagliflozin Dapagliflozin Empagliflozin Ertugliflozin |
Omit dose | Omit dose | Omit dose | |
| Sulfonylureas | Glibenclamide Gliclazide (inc. MR preparations) Glimepiride Glipizide Tolbutamide |
Continue | Omit morning dose | Omit morning and afternoon dose(s) | |
What to do with your insulin before surgery if FASTING.
What to do with your insulin before surgery if FASTING and if you are using:
Long acting Insulin
| Insulins | Example medications | Day prior to admission | Morning Procedure | Afternoon Procedure |
|---|---|---|---|---|
| Once daily long acting (morning) | Abasaglar Humulin l Insulatard Insuman Basal Lantus Levemir Semglee Tresiba Toujeo Xultophy |
No dose adjustment necessary | Give 80% of dose and blood glucose to be checked on admission | Give 80% of dose and blood glucose to be checked on admission |
| Once daily long acting (lunchtime) |
Give 80% of dose | Restart insulin at normal dose when eating and drinking starts. |
Restart insulin at normal dose when eating and drinking starts. |
|
| Once daily long acting (evening |
Give 80% of dose | No dose adjustment necessary | No dose adjustment necessary | |
| Twice daily (long acting insulin |
Morning dose will need to stay the same evening dose will need to be 80% |
Morning dose will need to be 80% and blood glucose to be checked on admission.The evening dose will remain unchanged |
Morning dose will need to be 80% and blood glucose to be checked on admission.The evening dose will remain unchanged |
Premixed insulin prepared by manufacturers
| Insulins | Example medications | Day prior to admission | Morning Procedure | Afternoon Procedure |
|---|---|---|---|---|
| Twice daily (premixed insulin) |
Humulin M3® Humalog Mix 25® Humalog Mix 50® Hypurin Porcine 30/70 Mix® Insuman Comb 15® Insuman Comb 25® Insuman Comb 50® Novomix 30® |
No dose adjustment necessary |
Halve usual morning dose. Blood glucose to be checked on admission Resume usual insulin with evening meal if eating a normal meal. If eating a half/small meal give half usual dose. If not eating give basal only component of the usual mixed insulin. | Halve usual morning dose. Blood glucose to be checked on admission Resume usual insulin with evening meal if eating a normal meal. If eating a half/small meal give half usual dose. If not eating give basal only component of the usual mixed insulin. |
| Three times per day (premixed insulin) |
No dose adjustment necessary |
Halve usual morning dose. Blood glucose to be checked on admission
Omit lunchtime dose Resume normal insulin with evening meal if eating a normal meal. If eating a half/small meal give half usual dose. If not eating give basal only component of the usual mixed insulin |
Halve usual morning dose. Blood glucose will be checked on admission
Omit lunchtime dose Resume normal insulin with evening meal if eating a normal meal. If eating a half/small meal give half usual dose. If not eating give basal only component of the usual mixed insulin |
Self-mixed insulin prepared by patient/carer
| Insulins | Example medications | Day prior to admission | Morning Procedure | Afternoon Procedure |
|---|---|---|---|---|
| Twice daily (two different types of insulin combined by the person with diabetes into one injection) |
Short acting: Actrapid® Apidra® Fiasp® Humalog® Humulin S® Hypurin® Porcine Neutral Insuman Rapid® Lyumjev® NovoRapid® Trurapi® Intermediate acting: Humulin I® Hypurin® Porcine Isophane Insulatard® |
No dose adjustment necessary |
Calculate the total dose of both morning insulins and give half of this total dose as intermediate acting insulin only, in the morning
Blood glucose to be checked on admission Resume usual insulin with evening meal if eating a normal meal. If eating a half/small meal give half usual dose. If not eating give basal only component of the usual mixed insulin |
Calculate the total dose of both morning insulins and give half of this total dose as intermediate acting insulin only, in the morning
Blood glucose to be checked on admission Resume usual insulin with evening meal if eating a normal meal. If eating a half/small meal give half usual dose. If not eating give basal only component of the usual mixed insulin |
Short acting insulin
| Insulins | Example medications | Day prior to admission | Morning Procedure | Afternoon Procedure |
|---|---|---|---|---|
| Short acting insulin with meals (two to four doses a day) | Short acting: Actrapid Apidra® Fiasp® Humalog® Humulin S® Hypurin® Porcine Neutral Insuman Rapid® Lyumjev® NovoRapid® Trurapi® |
No dose adjustment necessary |
Omit morning dose if no breakfast is eaten
Blood glucose to be checked on admission Omit lunchtime dose if not eating and Resume normal insulin with evening meal if eating a normal meal. If eating a half/small meal give half usual dose. If not eating give basal only component of the usual mixed insulin |
Take your usual morning insulin dose with your breakfast
Omit lunchtime dose if not eating Resume normal insulin with evening meal if eating a normal meal. If eating a half/small meal give half usual dose. If not eating give basal only component of the usual mixed insulin |
Insulin pump therapy
You should be able to continue to use your pump if your procedure requires you to miss no more than one meal.
Resume taking usual insulin the morning after surgery (procedure). However, blood glucose levels may be higher than usual for a day or so.
Advice for diabetic patients after surgery
- After your operation (procedure) your blood sugar will be checked and additional insulin given if necessary.
- After your operation (procedure) you will be offered food and drink when you feel able to eat.
If you are eating and drinking normally you should restart taking your normal insulin and tablets the next morning. However, your blood glucose levels may be higher than usual for a day or so.
When you get home, if you feel sick or are sick and are unable to eat, please contact your GP or nearest General Hospital.
Source: Centre for Perioperative Care. (2023, October). Guideline for Perioperative Care for People with Diabetes Mellitus Undergoing Elective and Emergency Surgery Updated October 2023.
Diabetes Overview – UKCPA Handbook of Perioperative Medicines
webpage last updated 15/04/2025