When you digest food and drink, carbohydrates are broken down into glucose. This passes into your blood and is used by the body as energy or is stored.

It is important to have enough sugar in your blood to provide energy for the organs in your body to work properly. There is an ideal range for your blood sugar level to provide this energy. Your diabetes team will talk to you about what your blood sugar levels should be. Lots of things can affect your blood sugar level.

How do I know what my blood sugar level is?

There are different ways to check your blood sugar level. Most people with type 3c diabetes will need to monitor their blood sugar level.

Blood sugar monitor 

If you need to check your blood sugar level regularly, you may be given a blood sugar monitor. Your diabetes nurse will show you how to use the monitor and tell you when and how often you should check your blood sugar level.

You will need to prick your finger to produce a small drop of blood, which is put onto a measuring strip in the monitor. The monitor tells you what your blood sugar level is within a few seconds.

Flash glucose monitors

These monitors are for people who take insulin. The monitor is attached to your arm, a bit like a plaster, with a small needle that sits just under your skin. This constantly measures your blood sugar levels. A flash glucose monitor means that you can easily check your blood sugar levels at any time, and you don’t need to regularly prick your finger.

If you are struggling to control your diabetes, speak to your diabetes team about whether a flash glucose monitor might be suitable for you. They are not widely available on the NHS, although you may be eligible for one if you have had a total pancreatectomy. You may be able to buy one yourself, although they are quite expensive.

Blood tests 

Some people don’t need to check their blood sugar levels regularly, so won’t need a blood sugar monitor. Your doctor or nurse will do blood tests to check your blood sugar levels. They may also ask you about any symptoms you have.

Diabetes UK have more information about testing your blood sugar levels.

What should my blood sugar level be?

Your diabetes team will talk to you about the target range for your blood sugar level. If your blood sugar level is in the target range, your body will get the energy it needs.

If you have pancreatic cancer, your target range will be specific to you. It may depend on lots of things, including your cancer and treatment, and how well you are. It may change over time. If you have lost weight, eating more calories and stabilising your weight might be more important than keeping your blood sugar levels in the target range all the time. Speak to your diabetes team about your target range.

How do I get my blood sugar level in the target range?

If you have type 3c diabetes, it can be hard to get your blood sugar level into your target range. Most people will need medicine to do this. This may be tablets and/or insulin injections. Read more about how diabetes is treated.

The diabetes team will explain how to take your diabetes medicine and help you manage the diabetes. It may take a few weeks before your blood sugar levels settle once you start treatment.

What can affect my blood sugar levels?

Blood sugar levels are affected by many things, including your treatment, illness, different food and drinks, activity levels, medicines and stress.

Some chemotherapy drugs are mixed in sugary liquids. Your oncology team should take your diabetes into account when providing the chemotherapy and monitor your blood sugar levels. Some people also find it harder to eat for a few days after having chemotherapy, which can affect your blood sugar levels. If you are having chemotherapy, it’s a good idea to monitor your blood sugar levels and let your oncology team know if these are higher or lower than normal.

Steroids are often given with chemotherapy, or may be used to treat some symptoms like sickness. These may also make your blood sugar levels rise. Talk to your diabetes nurse about managing your blood sugar levels if you are having steroids.

Diet and blood sugar levels

Different foods and drinks can affect your blood sugar levels. People with type 3c diabetes won’t usually be able to manage their diabetes by reducing how much sugar they eat.

It is important that you eat regularly and don’t skip meals. If you are taking diabetes medicine, it’s important to have some carbohydrate in your meals and snacks. Read more about carbohydrates. You may also need to take pancreatic enzymes when you eat, so that you are able to digest your food properly and absorb the nutrients from it.

If you measure your own blood sugar levels and they are often above your target range, then you will probably need more medicine to bring them down. Speak to your diabetes team about this. Don’t change or reduce what you are eating to bring your blood sugar levels down, unless this has been recommended by your diabetes team, as this could reduce the nutrition your body gets. And only change your diabetes medicine if your diabetes team tell you to.

Sugary drinks can cause a big rise in your blood sugar level. If you are eating and drinking well and maintaining your weight, it is best to avoid sugary drinks. You could try low calorie or sugar free drinks instead. Sometimes your dietitian may recommend sugary drinks for other reasons – for example, flat sugary drinks can help with feeling sick. Speak to your diabetes nurse or dietitian about how to manage your blood sugar level if you are having sugary drinks, snacks or puddings.

There is a lot of information online about changing your diet if you have diabetes – but this is mainly for people with other types of diabetes. Advice about diet for people with type 2 diabetes may not be right for you if you have type 3c diabetes.

“It was made clear to me that with the correct insulin and Creon® I could eat what I wanted.”

What if I have lost weight?

If you have lost weight you may need more calories and protein in your diet to help you put weight back on. Your dietitian can give you advice about this. It may include having foods or nutritional supplements that increase your blood sugar level. Your diabetes will need to be managed around this.

If your blood sugar levels are high, speak to your diabetes team. They may suggest changes to your medicine to help with this. Don’t avoid any foods or reduce how much you eat, unless your dietitian tells you to.

If you have lost weight, health professionals should work together to help manage this. This should include dietitians, the diabetes team and your GP.

Read more about putting on weight if you have pancreatic cancer.

Which foods affect my blood sugar levels?

When carbohydrates are eaten they are broken down into sugar, which makes your blood sugar levels rise.  Carbohydrates include starchy foods and sugars (see below).

Carbohydrates are an important source of energy and a key part of a healthy diet, so you should still eat food containing carbohydrate. It’s also important in preventing your blood sugar level dropping too low. Eating regular portions of starchy carbohydrates helps keep your blood sugar level constant, as the sugar is released more slowly from these. Sugary foods can cause sudden peaks in your blood sugar levels.

Speak to your dietitian for more information and advice about eating food containing carbohydrates.

Examples of foods containing carbohydrate

Starchy foods include:

  • bread, naan and chapatti
  • rice, cous cous and quinoa
  • potato, yam, cassava and plantain
  • pasta
  • cereals such as wheat, bran, oats, barley, rye, millet and maize
  • crackers and crispbread
  • pies and pastries
  • breaded and battered food.

Foods containing both starch and sugar include:

  • cakes
  • biscuits
  • sweet pastries
  • sugary breakfast cereal.

Sugary foods include:

  • ice cream
  • sweets, chocolates and mints
  • sugary fizzy drinks and squashes
  • fruit juices and smoothies
  • syrup and treacle
  • jam, marmalade and lemon curd
  • honey
  • chocolate spread.

Fruit, milk and yoghurt all contain sugar but have less effect on blood sugar levels than foods with added sugar like sweets, sugary drinks or ice cream. Fruit, milk and yoghurt also contain other important nutrients and can be eaten often as part of a healthy diet.

Which foods should not make my blood sugar levels rise? 

Foods low in carbohydrate should not make your blood sugar levels rise or drop. These include:

  • meat, fish, eggs, cheese, quorn®, soya protein and tofu
  • butter, margarine, lard, ghee, cream, cooking oils and oil-based dressings
  • vegetables (except potatoes) and salads
  • lentils, beans, pulses, nuts and seeds (although some people may find these do increase blood sugar levels)
  • herbs, spices, soy sauce and vinegars
  • small amounts of sauces and pickles.

Although these foods may not affect your blood sugar levels, most contain proteins and fats, so you will need to take pancreatic enzymes when you eat them.

Artificial sweeteners 

You don’t need to avoid sugar if you have type 3c diabetes – it can be part of a balanced diet. But a lot of sugar in your diet does make it harder to keep your blood sugar levels within your target range. You can use sweeteners instead of sugar if you want to reduce the amount of sugar you have.

There is a wide range of sweeteners available so try different varieties to find one you like. Some sweeteners may cause diarrhoea (runny poo), and you should avoid these. Check any brands with your dietitian.

‘Diet’ versions of sugary drinks won’t affect blood sugar levels. Diabetic foods aren’t recommended. They are expensive and can also cause diarrhoea.

What is hypoglycaemia (a hypo)?

If you have diabetes, you will hear the term hypoglycaemia or a ‘hypo’. This means a low blood sugar level of less than 4mmol/l. Some people find it helpful to remember ‘four is the floor’, so not to go below this.

A hypo can be caused by:

  • missing a meal, or having a meal or snack later than usual
  • eating less starchy food (carbohydrate) than usual
  • doing more exercise than usual
  • not taking enough pancreatic enzymes, or forgetting to take your enzymes with food or drinks
  • drinking alcohol without food
  • injecting too much insulin
  • being sick after taking your mealtime insulin.

Some treatments for diabetes increase how much insulin your pancreas makes. These include gliclazide and glimepiride. If the dose of these is too high, this can also cause a hypo.

Symptoms of a hypo include:

  • hunger
  • trembling
  • headache or light headedness
  • blurred vision
  • paleness
  • sweating and cold sweats
  • palpitations (fast or pounding heartbeat)
  • tingling lips
  • diarrhoea
  • mood changes, anxiety, irritability or aggression
  • problems concentrating.

How is a hypo treated?

There are two steps to treating hypoglycaemia. You must follow both of these steps to treat the hypo and prevent it happening again. It may be useful to share this information with the people you spend time with, particularly if you have recently been diagnosed with diabetes or if you don’t always recognise the symptoms of a hypo.

Step 1: Straight away, take 15-20g of fast acting carbohydrate (sugar). For example:

  • 4-6 dextrose or glucose tablets
  • 5 jelly babies
  • 5 fruit pastilles
  • 10 jelly beans
  • one 60ml bottle of Glucojuice®
  • about 200ml fruit juice.

Chocolate, milk and sugar added to drinks are not suitable options at this stage, as they won’t increase your blood sugar level fast enough.

Wait 10-15 minutes and check your blood sugar level. If it remains low (below 4mmol/l) repeat step 1. If it has come back to the target range (above 4mmol/l) then go to step 2.

If you have repeated step 1 three times and your blood sugar level is still below 4mmol/l then phone 999 for an ambulance.

Step 2: Eat 15 to 20g of starchy carbohydrate. This causes a gradual rise in your blood sugar level and can help to keep your sugar level steady after a hypo.

This could be a:

  • sandwich
  • piece of fruit
  • bowl of cereal
  • glass of milk
  • or your next meal, if it’s due.

Read more about foods containing carbohydrate.

If you take pancreatic enzymes, don’t forget to take these with step 2 of your hypo treatment. You don’t need enzymes with step 1.

Always keep something to treat a hypo with you when you are out and about. If you drive, keep something in the car. Read more about driving and diabetes.

You should also keep something to treat a hypo by the bed in case you have a hypo overnight. Night time hypos are more likely if you:

  • have been more active than usual during the day
  • had a blood sugar reading before bed that was less than 6mmol/l
  • had a hypo earlier that day
  • have taken fewer enzymes than you need, or have forgotten to take them
  • have had more than one alcoholic drink that day
  • your pancreas doesn’t produce enough glucagon.

If any of these have happened, you may need a bedtime carbohydrate snack to reduce the risk of a hypo. It is important that you don’t inject insulin with this snack as this could cause your blood glucose levels to drop too low. Do take your enzymes with the snack though.

If you have regular hypos, speak to your diabetes team. It’s likely that your diabetes medicine will need to be changed.

Diabetes UK have more information about hypoglycaemia.

Updated April 2021

Review date April 2023