Managing diabetes if you have pancreatic cancer – information about type 3c diabetes

Pancreatic cancer and surgery to remove the cancer can cause diabetes. This may be a type of diabetes called type 3c diabetes. This information is for people with pancreatic cancer and diabetes.

We also have information about diabetes as a symptom before people are diagnosed with pancreatic cancer, and diabetes as a risk factor of pancreatic cancer.

Key facts

  • Diabetes is a condition where the amount of glucose (a type of sugar) in your blood is too high.
  • Your pancreas normally makes hormones called insulin and glucagon which keep your blood glucose at the right level.
  • Pancreatic cancer or surgery for the cancer can stop your pancreas making enough of these hormones. This can cause type 3c diabetes.
  • Type 3c diabetes is different to type 1 and type 2 diabetes. A lot of information about type 1 and type 2 diabetes may not be right for you.
  • Symptoms of type 3c diabetes can include feeling thirsty, needing to pee more often, feeling hungry, losing weight without trying to, and feeling light-headed or confused.
  • There are ways to manage type 3c diabetes. Most people will need medicine to do this. This may be tablets or insulin injections.
  • You may see a diabetes specialist nurse and a specialist dietitian to help you manage your diabetes.
  • As well as making insulin and glucagon, your pancreas also makes enzymes which break down your food. Pancreatic cancer and surgery to remove the cancer can affect this. If you have type 3c diabetes you may have problems digesting your food. Pancreatic enzyme replacement therapy (PERT) helps with this.
  • It can be confusing managing diabetes when you have pancreatic cancer. Speak to your medical team if you have any questions or worries. They will work with you to manage your diabetes.

What are the symptoms of diabetes?

The symptoms for type 3c diabetes are similar to other types of diabetes and can include:

  • feeling thirsty
  • weight loss
  • needing to pee more often
  • fatigue
  • feeling lightheaded
  • palpitations
  • sweating
  • confusion.

“It is worthwhile looking out for symptoms of diabetes. It was only after I mentioned my partner’s unusual increased thirst and the need to go to the loo that he had a blood test which confirmed the diagnosis.”

What is type 3c diabetes?

Diabetes is a condition where the amount of glucose (a type of sugar) in your blood is too high. The amount of glucose in your blood is called your blood sugar level or blood glucose level.

The pancreas usually produces hormones called insulin and glucagon which keep the amount of glucose in your blood at the right level. If you have pancreatic cancer, you may not produce enough of these hormones. This means that your blood sugar level may become too high or too low.

There are different types of diabetes. You may have heard of type 1 and type 2 diabetes. Type 3c diabetes is different to these and is treated differently. It is caused by damage to the pancreas. It is sometimes called pancreatogenic or brittle diabetes.

People with pancreatic cancer, pancreatitis (inflammation of the pancreas) and people who have had surgery to remove part of the pancreas may get type 3c  diabetes. People who have had their whole pancreas (total pancreatectomy) removed will have type 3c diabetes.

What are insulin and glucagon?

Insulin and glucagon are hormones made in the pancreas. Hormones are chemical messengers carried in the blood which do specific things in the body. Insulin and glucagon keep the amount of glucose in your blood at the right level.

  • Insulin reduces the amount of glucose in your blood. It does this by moving glucose from the blood into cells in the body, where it is either stored or used for energy.
  • Glucagon helps to increase the amount of glucose in your blood when needed, by releasing glucose that is stored in your liver.

When you digest food and drink, carbohydrates are broken down into glucose. The glucose passes into your blood causing a rise in your blood glucose level. If you do not have diabetes and the glucose level goes above the usual range, the pancreas produces insulin which brings it down. If the glucose level goes below the usual range, the pancreas will produce glucagon to bring the level up again.

If you have type 3c diabetes, your pancreas may make less insulin and glucagon than your body needs. If your whole pancreas has been removed, your body will not make any insulin or glucagon.

Why is type 3c diabetes different to type 1 and type 2?

Type 3c diabetes is different to type 1 diabetes and type 2 diabetes.

  • People with type 1 diabetes can’t produce any insulin but make normal levels of glucagon. People with type 3c diabetes may produce less of all the hormones from the pancreas, including insulin and glucagon. If you have had your whole pancreas removed, you won’t produce any insulin or glucagon.
  • People with type 2 diabetes make insulin but it doesn’t work properly, and they need more to do the same job. In people with type 3c diabetes the insulin works properly but they don’t make enough of it.

The different types of diabetes need to be treated differently. This means that the usual treatment for type 1 or type 2 diabetes may not be right for you if you have type 3c diabetes. If you already had type 1 or 2 diabetes before being diagnosed with pancreatic cancer, your diabetes may now need to be treated differently. Most people with type 3c diabetes will need to take medicine, which may be tablets and/or insulin injections.

You may find that type 3c diabetes isn’t as well-known as type 1 or type 2 diabetes. A lot of the information available about diabetes is for people with type 1 or 2 diabetes and may not be relevant to you. For example, there is a lot of information that encourages people with type 2 diabetes who are overweight to lose weight. This won’t be relevant to people with type 3c diabetes who have lost weight or are struggling to put weight back on.  

Diabetes and problems digesting food

If you have type 3c diabetes, you are likely to also have problems digesting your food.

As well as insulin and glucagon, the pancreas also makes enzymes which break down your food. If you have pancreatic cancer, your pancreas may not make enough of these enzymes, or they may be blocked from getting to the part of your bowel where they are needed. This means that food is not properly digested.

You can take capsules to replace the enzymes that your pancreas would normally make. This is called pancreatic enzyme replacement therapy (PERT) and will help you digest your food.

If you have problems digesting your food, you won’t be fully digesting carbohydrates in your food. This means that less glucose will be absorbed into your blood. Once you start taking the pancreatic enzymes, your blood sugar level may rise because you will be digesting your food again.

This can change how your diabetes needs to be managed, and it may need to be monitored more regularly. If you notice your blood sugar levels have gone up, speak to your diabetes team as they may need to change your medicine. It’s important that blood sugar levels are treated with medicine and not by reducing how much PERT you take.

Read our fact sheet about diabetes

You can read more about diabetes, including how to manage it, in our fact sheet:

Diabetes if you have pancreatic cancer: Information about type 3c diabetes.

We also have a diary you can use to help you monitor your diabetes:

Diary for monitoring your diabetes

Download our diabetes fact sheet

Who treats diabetes?

Who you see to treat your diabetes may depend on services in your local area.

You may see a diabetes specialist nurse who will teach you how to monitor your blood sugar levels and help manage your diabetes medicine. You may also see a specialist dietitian, such as a diabetes, pancreatic or oncology dietitian, to help you manage your diabetes. Make sure you tell them that you have type 3c diabetes and pancreatic cancer. If you haven’t seen a specialist dietitian, ask your doctor or nurse to refer you to one. Your GP and hospital doctors may also help manage your diabetes.

Make sure you know who to contact about your diabetes. If you are not sure, ask your medical team.

It can be difficult and confusing to manage diabetes if you have pancreatic cancer. Your dietitian and diabetes nurse will help you manage your blood sugar levels and give you advice about how to live well with your diabetes.

If you have any questions, ask your dietitian, doctor or diabetes nurse. You can also speak to our specialist nurses on our free Support Line who can explain more about managing diabetes.

Questions about diabetes?

If you have any questions, it is important that you speak to your dietitian or diabetes nurse. You can also speak to our specialist nurses on our free Support Line who can explain more about managing diabetes.

Speak to our nurses
Specialist nurse Nicci

Questions to ask your doctor, nurse or dietitian


  • Why have I developed diabetes?
  • Will having surgery mean I develop diabetes?
  • Do I have type 3c diabetes?
  • How should I manage my diabetes?
  • Who can help me manage my diabetes?
  • Will I need to monitor my blood sugar levels? How should I do this?
  • Who should I contact if my blood sugar levels are not in the target range?
  • Will I need to take tablets or insulin?
  • How do I take insulin?
  • How should I manage my diet if I have diabetes and pancreatic cancer?

Acknowledgements and references


We would like to thank the following people who reviewed this information.

  • Laura McGeeney, Pancreatic Specialist Dietitian, Addenbrooke’s Hospital
  • Rachel Ewing, Advanced Practice Diabetes Dietitian, Ulster Hospital
  • David Bourne, Specialist Dietitian, Freeman Hospital
  • Pancreatic Cancer UK Lay Information Reviewers
  • Pancreatic Cancer UK Specialist Nurses

References

Email us at publications@pancreaticcancer.org.uk for references to the sources of information used to write this information.

Updated June 2023

Review date June 2026