Diabetes and planning your cancer treatment

Diabetes may be more difficult to manage during cancer treatment. Your may need more tests or closer monitoring before and during treatment.

Reducing your risk of long-term health problems

Diabetes can cause long-term health problems, such as:

  • damage to the heart and blood vessels (cardiovascular disease)
  • nerve damage (neuropathy)
  • kidney damage (nephropathy)
  • damage to the blood vessels in the eye (retinopathy).

Some cancer treatments can also cause these problems, or make them worse in people who already have them. If you have diabetes, you will often need extra tests and investigations to check your health. These tests will make sure you are well enough to have cancer treatment.

During treatment, you may need to be monitored more closely than people who do not have diabetes. If the side effects from treatment become very severe, your cancer treatment may need to be adjusted or changed. Your cancer doctors will sometimes suggest a different type of cancer treatment.

Adjusting or changing your cancer treatment may affect how well it works. But not changing it may cause serious long-term health problems. Your cancer doctor will talk to you about the benefits and risks of your treatment. You will be involved in any decisions to change your treatment.

Diabetes UK has more information on the other health problems that diabetes can cause.

Controlling your blood sugar

When you are ill or stressed, the amount of sugar in your blood increases. This helps your body fight the illness or deal with the stress. People who do not have diabetes will produce more insulin to stop the sugar level getting too high. But if you have diabetes, your blood sugar level can keep getting higher.

While you are having cancer treatment, it is important to try to keep your blood sugar in a safe range. This is not always possible, and a slightly high blood sugar level is not a big problem if it is only for a short time. But very high blood sugars can be a problem. They can cause symptoms such as being more thirsty and needing to pee a lot. This can lead to dehydration. Get advice from your diabetes team if you notice these symptoms.

Having high blood sugars may increase the risk of developing other problems while you are having cancer treatment. These can include infection and wounds not healing properly.

Your diabetes treatment can be changed to fit around your cancer treatment if needed. During cancer treatment, you may need to change your diabetes medicine to control the amount of sugar in your blood.

Most people with diabetes know how to manage their food and medicines. They may not find it difficult to keep their blood sugar levels normal during treatment. You may need more help if:

  • you have only recently been diagnosed with diabetes
  • you often have problems controlling your sugar levels
  • if you have lost a lot of weight before cancer treatment.

Before you start your cancer treatment, talk to your diabetes nurse or ask to see one. They can give you more advice.

Some people with diabetes, especially those with type 2, may not monitor their blood sugar level. You may need to start monitoring it while having cancer treatment. Your cancer doctor or diabetes team can give you advice before you start treatment. If you do not already have monitoring equipment, ask your diabetes team for some. The diabetes team can tell you:

  • how to test your blood sugar
  • how many times to test a day
  • the sugar level you should be aiming for.

You should be given the contact number of a diabetes specialist. You can call them to talk about any worries you have about your diabetes. 

Going into hospital

You may need to spend some time in hospital during or after your cancer treatment. This will depend on the type of cancer you have and the treatment that is planned. You may only have to stay in hospital for a few hours. But you may have to stay longer.

You will usually know when you are going into hospital. This means you can plan to make sure that you have everything you need to manage your diabetes.

Your blood sugar levels may be higher or lower than usual while you are in hospital. This can happen because you are being less active and eating different food. It can also be caused by the stress of being in hospital. Your blood sugar will be checked regularly. Your doctors may need to adjust your diabetes treatment. They will talk to you about this first.

All the ward staff should know that you have diabetes. You should tell them when you first meet. They should also know about your diabetes care. If you cannot give them this information, they can contact your local diabetes team. You may also find it helpful to talk about your care with the hospital’s diabetes team, if there is one.

Being in hospital and having cancer treatment can make it more difficult to manage your diabetes. If you need help to control your blood sugar, it is important to ask the team looking after you.


Diabetes equipment

When you go into hospital, you may want to take your own diabetes equipment. This could include your:

  • blood testing kit
  • insulin pen
  • insulin pump, if you use one.

The hospital may not use the equipment you are used to. And they may not have all the equipment you need. Before you go in, you could talk to the staff about what they have and what you would like to bring.

The nurses will check your blood sugar using the hospital equipment. You can use your own blood testing kit too, if you prefer.


Diabetes medicines

If you are admitted to hospital overnight or longer, take your insulin or tablets with you. The hospital pharmacy should be able to give you the medicines you normally use. Or they may give you something similar. Not every ward or unit will have all the different drugs used to treat diabetes. This means it can sometimes take a while to get them.

You may only spend a few hours in hospital at a time. For example, this might be if you are having chemotherapy in a day unit. It is a good idea to take some food and your medicines with you. Try to keep to your normal routine as much as you can.

This information was produced in partnership with Diabetes UK.
In partnership with Diabetes UK. Know diabetes. Fight diabetes.
Image: Diabetes UK