From Clinic to Recovery · First Edition
Chapter 18 — Diabetes and Diabetes Medicines, Including SGLT2 Inhibitors
Dr. Tamer Rushdy Elalfy · 14 min read
In this chapter
Diabetes is common among surgical patients, especially in the Gulf, and it affects every stage of surgery: wound healing, infection, kidney function, and recovery. Patients often take several medicines, each with its own rules before surgery, and the rules have changed as newer drugs have arrived. SGLT2 inhibitors, now used for heart and kidney protection as well as diabetes, can cause ketoacidosis around surgery even when blood glucose is normal. Patients with diabetes are usually experts in their own condition, and the best plans are made with them, not for them. This chapter gives the principles; detailed dosing should follow the hospital’s protocol and the advice of the diabetes and anesthesia teams.
Learning objectives After reading this chapter you should be able to:
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Table 18.1. Diabetes and surgery at a glance.
| At a glance | |
|---|---|
| Before elective surgery | HbA1c below about 8 to 8.5 percent where possible, without delaying urgent or cancer surgery |
| Glucose target around surgery | About 100 to 180 mg/dL (5.6 to 10 mmol/L) |
| SGLT2 inhibitors | Stop 3 to 4 days before (US guidance) or the day before and day of surgery (UK guidance); restart only when eating normally |
| On the day | First on the list; check glucose on arrival and every 1 to 2 hours while fasting |
| The key counseling message | “Your diabetes plan for surgery is written down for you. Follow it exactly, check your sugar, and tell us early if you feel unwell.” |
STEP 1 Explaining why diabetes matters and making the plan
18.1 Why diabetes matters for surgery
High blood glucose around surgery increases wound infection and other complications, and low glucose under anesthesia can go unnoticed. Before elective surgery, an HbA1c below about 8 percent is recommended where it can be achieved [1]; UK guidance suggests optimizing control when HbA1c is above about 8.5 percent (69 mmol/mol) [2]. Optimization should not delay surgery for cancer or other urgent conditions. Around surgery, a glucose target of about 100 to 180 mg/dL (5.6 to 10 mmol/L) balances the risks of high and low glucose [1].
Script: explaining the plan “Your diabetes affects how you heal and your risk of infection, so we plan your medicines carefully around the operation.” “You will get a written plan that tells you which medicines to take, which to stop, and when to restart each one. Please bring your medicines and your glucose meter on the day.” “We will put you first on the operating list if we can, so you do not fast longer than needed.” |
18.2 Diabetes medicines before and after surgery
Table 18.2 summarizes the usual approach for each class of medicine. Guidance differs between countries and is updated often; for example, the American Diabetes Association advises stopping SGLT2 inhibitors 3 to 4 days before surgery [1], while a 2025 UK consensus advises omitting them the day before and the day of the procedure [3]. Each hospital should adopt one protocol, and each patient should receive a written, personal plan (Figure 18.1).
Table 18.2. Usual approach to diabetes medicines around surgery. Always follow the hospital protocol.
| Medicine | Before surgery | After surgery |
|---|---|---|
| Metformin | Usually omitted on the day of surgery, according to protocol; longer if contrast or kidney concerns | Restart when eating and drinking, if kidney function is normal |
| Sulfonylureas (for example, gliclazide) | Omit on the day of surgery: risk of low glucose while fasting | Restart when eating normally |
| DPP-4 inhibitors (for example, sitagliptin) | Often continued; follow protocol | Continue when eating |
| SGLT2 inhibitors (for example, empagliflozin, dapagliflozin) | Stop 3 to 4 days before (4 for ertugliflozin) [1], or the day before and day of surgery [3] | Restart only when eating and drinking normally; after major surgery, not until ketones are normal [4] |
| GLP-1 and GIP/GLP-1 injections | See Chapters 2 and 23 | See Chapter 23 |
| Long-acting (basal) insulin | Usually continued at a reduced dose, often about 75 to 80 percent the night before or morning of surgery [1] | Continue; adjust with glucose readings |
| Intermediate (NPH) or premixed insulin | Usually about half the usual morning dose, according to protocol | Return to usual doses as eating resumes |
| Insulin pump | Continue basal rate for short procedures, with an agreed plan; never stop without an alternative | Resume usual settings when eating |
[Figure — diagram omitted in this text edition; see the figure caption below and the Word chapter file for the image]
Figure 18.1. A typical timeline for diabetes medicines around planned surgery.
18.3 SGLT2 inhibitors and euglycemic ketoacidosis
SGLT2 inhibitors increase ketone production, and during fasting, surgery, or illness they can cause diabetic ketoacidosis with a normal or only slightly raised glucose level. This makes it easy to miss. Patients may feel nauseated, vomit, have abdominal pain, breathe quickly, or feel generally unwell. Blood ketones should be measured in any patient taking an SGLT2 inhibitor who becomes unwell around surgery, whatever the glucose level, and the medicine should not be restarted after major surgery until ketones are normal and the patient is eating and drinking [4].
Caution: euglycemic ketoacidosis
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18.4 Low blood glucose
Hypoglycemia, a glucose below about 70 mg/dL (4 mmol/L), is most likely in patients taking insulin or sulfonylureas who are fasting. Teach patients and nurses the signs (shaking, sweating, hunger, confusion, unusual behavior) and the treatment: 15 to 20 g of fast-acting glucose, such as a small glass of juice or glucose tablets, a repeat glucose check after 15 minutes, and a snack once glucose has recovered. Before surgery, a patient who is fasting can still take clear glucose drinks within the fasting rules (Chapter 2).
STEP 2 The day of surgery, recovery, and Ramadan
18.5 The day of surgery and after
- Arrival. Bring medicines, insulin, the glucose meter, and the written plan. Glucose is checked on arrival.
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Monitoring. Glucose is checked every 1 to 2 hours while fasting and during surgery, and before meals afterward.
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Longer fasting. Patients who will miss more than one meal, or whose glucose is poorly controlled, may need an intravenous insulin infusion according to protocol.
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Wounds and feet. Diabetes slows healing and increases infection. Protect the heels and feet from pressure in bed, and check them daily.
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Discharge. Give a written plan for restarting each medicine, sick-day rules, and who to call.
[Figure — diagram omitted in this text edition; see the figure caption below and the Word chapter file for the image]
Figure 18.2. Sick-day rules after surgery, for use with patients.
18.6 Ramadan and surgery
Planned surgery is best timed outside Ramadan for people with diabetes when possible. After surgery, recovery, irregular eating, and changes to medicines increase the risks of fasting, and patients should not fast until they have recovered and their diabetes is stable. The International Diabetes Federation and Diabetes and Ramadan International Alliance guidelines provide a framework for assessing risk and adjusting medicines for fasting; patients who wish to fast after recovery should have an individual plan with their diabetes team [5].
Table 18.3. Ramadan, diabetes, and surgery.
| Situation | Usual advice |
|---|---|
| Planned surgery | Schedule outside Ramadan if possible |
| Recovering from surgery | Do not fast until recovered, eating normally, and glucose stable |
| Taking an SGLT2 inhibitor | Higher risk of dehydration and ketoacidosis when fasting; agree a plan with the diabetes team |
| Taking insulin or sulfonylureas | Doses usually need changing for fasting; plan before Ramadan |
| Wishing to fast after recovery | Individual risk assessment and medicine plan with the diabetes team [5] |
STEP 3 Questions patients ask
“Why do I need to stop my tablet days before the operation?”
Some tablets, called SGLT2 inhibitors, can cause a dangerous acid build-up in the blood when you are fasting or unwell, even if your sugar looks normal. Stopping them before surgery prevents this [1].
“Should I take my insulin on the morning of surgery?”
Usually you take a reduced dose of your long-acting insulin, but not your mealtime insulin. Follow your written plan exactly.
“What if my sugar goes low while I am fasting?”
Drink a small glass of clear juice or take glucose tablets, check again in 15 minutes, and tell the staff when you arrive.
“Why is my sugar high after the operation?”
Surgery and stress raise sugar levels. We will check it often and adjust your treatment until it settles.
“Will diabetes slow my healing?”
It can. Keeping your sugar in the target range, stopping smoking, and eating enough protein help your wound heal.
“When can I restart my tablets?”
Most can restart when you are eating and drinking normally. An SGLT2 inhibitor should wait until you are eating normally, and after a big operation until your ketones are normal [4].
“Can I fast in Ramadan after my operation?”
Not until you have recovered and your diabetes is stable. If you wish to fast, plan it with your diabetes team [5].
“I have an insulin pump. Will I have to take it off?”
For short operations, many people keep their pump on its basal rate with an agreed plan. For longer operations, we may switch to an insulin drip. Never stop insulin completely.
STEP 4 Risks, warning signs, and consent
18.7 Additional risks with diabetes
Table 18.4. Additional risks for people with diabetes having surgery. Square brackets mark figures to replace with unit data.
| Band | Risk | Typical frequency | Example wording |
|---|---|---|---|
| Common | High glucose after surgery | Many patients | “Your sugar will probably be higher for a few days.” |
| Less common | Wound infection or slow healing | Higher than in people without diabetes [unit data] | “Diabetes raises the chance of a wound infection.” |
| Less common | Low glucose while fasting | [unit data] | “We check often to catch low sugar early.” |
| Rare but serious | Ketoacidosis, including with normal glucose on SGLT2 inhibitors | [unit data] | “Rarely, an acid build-up can make you very unwell. This is why we stop some tablets.” |
| Rare but serious | Kidney injury with dehydration, especially on metformin or SGLT2 inhibitors | [unit data] | “Keep drinking, and follow sick-day rules if you are unwell.” |
18.8 Checklist
Before surgery ☐ HbA1c checked; optimization considered for elective surgery, without delaying urgent surgery. ☐ Every diabetes medicine recorded, including SGLT2 inhibitors taken for heart or kidney disease. ☐ Written, personal medicine plan given for before, the day of, and after surgery. ☐ First on the operating list where possible. ☐ Hypoglycemia treatment and sick-day rules taught, with teach-back. ☐ Ramadan plans discussed where relevant. ☐ Diabetes team involved for complex regimens, pumps, or poor control. |
18.9 Warning signs
Table 18.5. Green, amber, and red warning signs for people with diabetes after surgery.
| Level | Signs | What to do |
|---|---|---|
| Green | Glucose a little higher than usual for a few days after surgery | Expected. Keep checking and follow your plan. |
| Amber | Glucose above about 250 mg/dL (14 mmol/L) on two checks Glucose often below 70 mg/dL (4 mmol/L) A wound that is red, warm, or leaking | Call the clinic or diabetes team the same day. |
| Red | Vomiting, abdominal pain, fast breathing, or drowsiness, especially if taking an SGLT2 inhibitor, even with a normal sugar Blood ketones raised Low sugar that does not recover after treatment, or confusion | Go to the emergency department now. Say that you have diabetes and which tablets you take. |
Key points
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STEP 5 Patient education guide
The following pages may be photocopied and given to patients. Complete the personal medicine plan with the patient, and add your unit’s name, phone numbers, and review date before use.
PATIENT GUIDE Diabetes and Your Operation Your personal medicine plan. Bring it, with your medicines and meter, on the day. |
My operation
Date: ______________________ Arrive at: ______________________
My medicine plan
| Medicine and dose | Days before | Day before | Morning of surgery | Restart |
|---|---|---|---|---|
Before the operation
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Check your sugar more often in the days before, and on the morning of surgery.
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Bring your medicines, insulin, meter, and this plan.
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If your sugar is low while fasting, drink a small glass of clear juice or take glucose tablets, and tell the staff.
If your sugar is low (below 70 mg/dL or 4 mmol/L)
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Take 15 to 20 g of fast sugar: a small glass of juice or glucose tablets.
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Check again after 15 minutes. Repeat if still low.
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When it is back up, eat a snack or meal.
After the operation
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Your sugar may be higher for a few days. Keep checking it.
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Restart your medicines as written in your plan.
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If you take an SGLT2 tablet (for example, empagliflozin or dapagliflozin): restart only when you are eating and drinking normally.
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Look after your feet and wound. Tell us about any redness or leaking.
If you are unwell: sick-day rules
[Figure — diagram omitted in this text edition; see the figure caption below and the Word chapter file for the image]
Ramadan
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Do not fast until you have recovered and your sugar is stable.
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If you wish to fast, make a plan with your diabetes team first.
Warning signs: when to get help
| Level | What you notice | What to do |
|---|---|---|
| GREEN | Sugar a little higher than usual for a few days | Keep checking and follow your plan. |
| AMBER | Sugar above 250 mg/dL (14 mmol/L) twice; frequent low sugar; a red or leaking wound | Call us or your diabetes team today. |
| RED | Vomiting, tummy pain, fast breathing, or drowsiness, even with a normal sugar; high ketones; low sugar that will not come up; confusion | Go to the emergency department now. Say you have diabetes and show your medicines. |
My contacts Surgical team: ______________________ Diabetes team: ______________________ Out of hours: ______________________ [Unit name] [Guide version and review date] |
References
1. American Diabetes Association Professional Practice Committee. 16. Diabetes care in the hospital: Standards of Care in Diabetes—2026. Diabetes Care. 2026;49(Suppl 1).
2. Centre for Perioperative Care. Guideline for perioperative care for people with diabetes mellitus undergoing elective and emergency surgery. London: CPOC; 2021, updated 2022.
3. El-Boghdadly K, Dhesi J, Fabb P, et al. Elective peri-operative management of adults taking glucagon-like peptide-1 receptor agonists, glucose-dependent insulinotropic peptide agonists and sodium-glucose cotransporter-2 inhibitors: a multidisciplinary consensus statement. Anaesthesia. 2025;80(4):412-424. doi:10.1111/anae.16541
4. Medicines and Healthcare products Regulatory Agency. SGLT2 inhibitors: monitor ketones in blood during treatment interruption for surgical procedures or acute serious medical illness. Drug Safety Update. March 2020.
5. Hassanein M, Afandi B, Yakoob Ahmedani M, et al. Diabetes and Ramadan: practical guidelines 2021. Diabetes Res Clin Pract. 2022;185:109185.
Note: references are numbered within this chapter for the pilot. Items marked in square brackets are collected in the Author Fill-in and Verification Log.