Medical Oncologist
CION Cancer Clinics
Having cancer surgery when you have diabetes | CION Cancer Clinics
Yes, you can usually have cancer surgery with diabetes. It rarely rules an operation out, but your sugar needs a plan. High sugar slows healing and raises the chance of infection, and fasting can drop it too low. Your team checks your HbA1c, gives written instructions for each medicine, and monitors your sugar closely around the operation. This page explains what to expect and what to ask. CION Cancer Clinics’ surgical oncologists in Hyderabad can talk this through with you.
MI
Medically reviewed by Dr. Mohammed ImaduddinConsultant Surgical Oncologist · MBBS, MS (General Surgery), MCh (Surgical Oncology) · last reviewed September 2026, next review due September 2027
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On this page
- Can you have cancer surgery if you have diabetes?
- How is your sugar managed from the check-up to going home?
- What happens to your diabetes medicines before surgery?
- How can you tell whether sugar is too high or too low?
- What do families believe about diabetes and surgery?
- What does your team weigh, and what can this page not tell you?
- Common questions about surgery with diabetes
The short answer
Can you have cancer surgery if you have diabetes?
Yes. Many people having cancer surgery have diabetes, and it rarely rules an operation out. What it does mean is that your sugar needs a plan before, during and after surgery, because both very high and very low sugar make an operation less safe.
Why sugar matters around an operation
High sugar slows wound healing and makes infections, in the wound, the chest and the urine, more likely. Surgery itself pushes sugar up, because stress hormones rise whether or not you have diabetes. Fasting before the operation can push it the other way, especially if you take insulin or certain tablets.
What your team looks at first
They want to know how well controlled your sugar has been over the last few months, which is what the HbA1c test shows. They also check your kidneys, heart and eyes, because long-standing diabetes can quietly affect all three, and each changes how an anaesthetic is planned.
When control is poor
If your HbA1c is high, the team may want a short period of tighter control before a planned operation. With cancer, that delay is weighed against how urgently the tumour needs removing. Sometimes surgery goes ahead with closer sugar monitoring instead.
The usual plan
How is your sugar managed from the check-up to going home?
At the pre-anaesthetic check-up
Bring every medicine strip, insulin pen and your sugar diary. The anaesthetist gives you written instructions for each medicine in the days before surgery. Ask them to write down what to do if your sugar runs low while you are fasting, and keep glucose tablets or juice with you on the way to hospital.
The morning of surgery
Your sugar is checked when you arrive. People with diabetes are often put first on the list, so the fasting time stays short.
During the operation
The anaesthetist checks your sugar regularly. For longer operations, insulin and glucose may run through a drip to hold it steady.
After surgery and going home
Frequent finger-prick checks continue until you eat normally. Your usual medicines restart when the team says, and you leave with clear instructions.
Not sure whether this applies to you?
Ask an oncologistYour medicines
What happens to your diabetes medicines before surgery?
Different medicines are handled differently. Never stop, skip or change one on your own. Your anaesthetist and the doctor who prescribes them will set the timing.
Metformin
Common brands include Glycomet and Glyciphage. It is often paused around the operation, particularly if you will have a contrast scan or your kidneys are affected.
Gliflozin tablets
Dapagliflozin and empagliflozin, sold as Forxiga, Jardiance and many other names. These are usually stopped ahead of surgery because, with fasting, they can cause a dangerous build-up of acid in the blood.
Insulin
Rarely stopped completely. The dose is usually adjusted the night before and on the morning of surgery, so your sugar does not fall while you are fasting.
Weekly injections
Semaglutide and similar injections slow how fast the stomach empties, which matters for a safe anaesthetic. Tell the team about these, even if you take them for weight.
Sulphonylureas such as glimepiride and gliclazide can cause low sugar while fasting, so they also get specific instructions.Know the signs
How can you tell whether sugar is too high or too low?
Sugar too low
Sugar too high
Sweating, shaking and a fast heartbeat
Very thirsty and passing a lot of urine
Sudden hunger, irritability or confusion
Tired, drowsy and hard to wake properly
More likely when fasting on insulin or some tablets
More likely with infection, steroids or stress
Treated quickly with glucose, then a meal
Treated with fluids and insulin as the team directs
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One thing that cannot wait
After you go home, if the person is vomiting and cannot keep food or medicines down, is breathing fast, is confused, or has very high or very low sugar that is not settling, go to the nearest emergency department the same day. Say they have diabetes and have just had surgery. Do not wait to see whether it passes overnight.
Commonly believed
What do families believe about diabetes and surgery?
"Diabetic people's wounds never heal, so surgery is not worth it."
Wounds heal in most people with diabetes. Good sugar control, stopping smoking and eating enough protein all help. Healing can be slower, which is why the wound is watched more closely.
"Skip the sugar tablets on the morning of surgery to be safe."
Some should be stopped and some should not. Guessing can leave sugar too high or too low. Follow the written instructions for each medicine exactly, and ask if anything is unclear.
"Once I start insulin in hospital, I will need it for life."
Insulin is often used for a short time around surgery because it is easy to adjust. Many people go back to their usual tablets once they are eating and recovering.
"Sugar-free sweets and fasting will bring the sugar down fast."
Crash dieting before surgery leaves you weak, and weight loss at this stage slows recovery. Aim for regular balanced meals and enough protein instead.
Being straight with you
What does your team weigh, and what can this page not tell you?
Whether and when to operate is decided by your surgeon and anaesthetist, often with a physician or diabetes specialist. They weigh your sugar control, the size of the operation, any damage diabetes has done to your heart or kidneys, and how urgent the cancer is.
When extra care is needed
Diabetes that has affected the kidneys, the heart or the nerves of the stomach needs more planning. So does diabetes treated with steroids for another illness. Some people also go home on insulin for a short while, and a family member may need to learn the finger-prick test.
Questions worth asking
Which of my medicines do I take, and which do I hold, and until when? What sugar readings should worry me at home? Who do I call if my sugar runs high after discharge?
This page cannot give you your own medicine plan or target readings. Those depend on your type of diabetes, your treatment and your operation, and only your team can set them.
Questions we are asked
Common questions about surgery with diabetes
Will my operation be cancelled if my sugar is high on the day?
Not automatically. A mildly raised reading on the morning of surgery is common and can be brought down with insulin. If the sugar is very high, or there are signs of acid building up in the blood, the anaesthetist may delay the operation until it is safe. They will explain the reason to you.
What is HbA1c and why do they keep asking about it?
HbA1c is a blood test that shows your average sugar over roughly the last three months, rather than on one day. It tells the team how well controlled your diabetes has really been. A high HbA1c is linked to more wound and chest infections, so it helps them decide how much preparation you need.
Can I drink water on the morning of surgery?
Most people are allowed clear water until a set time before the operation, but the rules differ between hospitals and operations. Follow the fasting instructions you are given. If you feel shaky or sweaty while fasting, check your sugar and tell the nurse straight away rather than waiting.
Why is my sugar high after surgery when it is usually controlled?
Surgery triggers stress hormones that raise sugar in everyone. Pain, infection, lying in bed and some medicines, especially steroids, push it higher. This usually settles as you recover. The team may use insulin for a while to keep readings steady during that period.
Does chemotherapy affect diabetes too?
It can. Steroids given to prevent sickness with chemotherapy often push sugar up, and poor appetite can pull it down. If you have chemotherapy before or after surgery, ask your oncologist to coordinate with whoever manages your diabetes, and check your sugar more often on treatment days.
What should I eat before surgery if I have diabetes?
Regular meals with enough protein, vegetables and controlled portions of rice or roti. Do not crash diet. If you are losing weight or eating poorly because of the cancer, ask to see a dietitian, because building up strength matters as much as keeping sugar steady.
Will someone at home need to check my sugar?
Often yes, at least for the first days. If you are going home on insulin or with changed medicines, ask the nurses to teach a family member the finger-prick test and what to do with the reading. Write down who to call before you leave the ward.
Does diabetes change what surgery costs?
It can add tests, a physician's review and sometimes a longer stay, so the final bill may differ from the first estimate. Aarogyasri, CGHS, ECHS, EHS and most cashless insurers cover approved cancer surgery. Call the helpline with your scheme or policy details and we will check what applies.
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MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
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Dr. Vinay Mamidala
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Dr. Vajja Sandeep Kumar
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Sources
- NICE — Perioperative care in adults (NG180)
- NICE — Type 2 diabetes in adults: management (NG28)
- NHS — Diabetes
- Macmillan Cancer Support — Surgery for cancer
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
The Pre-Anaesthetic Check-Up ExplainedWhere your medicine instructions are givenSurgery With Kidney Disease or on DialysisIf diabetes has affected your kidneysNutrition Before Cancer SurgeryEating to build strength without letting sugar climbMedicines Around Cancer SurgeryHow other regular medicines are handled around an operation
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Have diabetes and an operation coming up?
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