Planning cancer treatment when you have diabetes

Your cancer treatment will be planned by a team of health professionals. They will often ask your diabetes team for advice.

Having diabetes can make cancer treatment more complicated. If necessary, your diabetes treatment can be changed to fit around your cancer treatment. You may need to change your diabetes medicine to keep a safe amount of sugar in your blood. Contact your diabetes team before your treatment starts. They can give you extra support during your cancer treatment if you need it.

You may have to spend some time in hospital. It is a good idea to plan ahead so that you have everything you need to manage your diabetes. You may want to take your own equipment and diabetes medicines with you. Try to stick to your normal routine as much as possible.

You will have tests and scans to help plan your treatment. Most tests will have no effect on your diabetes, but it’s a good idea to contact the hospital before a test and tell them you have diabetes. They will give you advice.

How treatment is planned

Your cancer treatment will be planned by a team of health professionals. This team is called a multi-disciplinary team (MDT). Depending on what type of cancer you have, this may include a:

  • surgeon
  • medical oncologist – a doctor who specialises in treating cancer with chemotherapy and targeted therapy
  • clinical oncologist – a doctor who specialises in treating cancer with radiotherapy, chemotherapy and targeted therapy
  • radiologist – a doctor who specialises in reading scans and x-rays
  • pathologist – a doctor who specialises in looking at cells under a microscope and diagnosing the cell type
  • nurse specialist – a nurse who gives you information and support during treatment.

Your MDT will often include a pharmacist. They can give you information and advice about your medicines.

Your MDT will not usually include a diabetes specialist doctor or nurse. But some larger cancer centres may have one working as part of the team. If you have been diagnosed with diabetes, your diabetes team will often be asked for advice. When you meet your cancer doctor and specialist nurse you can ask if they have discussed your treatment with your diabetes team.

Some people have the option of joining a cancer research trial as part of their cancer treatment. These are called clinical trials. They are done to try to find new and better treatments for cancer. All clinical trials have strict guidelines about who can take part. Having diabetes may mean you cannot take part. Your cancer specialist can tell you whether you are suitable for a specific trial.


Managing two conditions

Having diabetes can sometimes complicate cancer treatment. Some cancer treatments can affect the amount of sugar in your blood. This means you and your cancer specialist may need to plan treatment more carefully. You may understand your diabetes and know the best way to manage it better than the team treating your cancer. It is important that your needs are considered and you're involved in planning your treatment.

If necessary, your diabetes treatment can be changed to fit around your cancer treatment. During treatment, you may need to change your diabetes medicine to keep a safe amount of sugar in your blood.

Some cancer treatments, such as chemotherapy, are given in cycles. This means you will have days when you have treatment, followed by days when you have no treatment (rest days). The level of sugar in your blood may go up and down at different times during each cycle of treatment, making it more difficult to manage. Your cancer doctor or specialist nurse will talk to you about your treatment plan.

Short-term increases in blood sugar are unlikely to have a long-term effect on your diabetes. But you may wish to talk to your diabetes team about possible ways to correct the higher blood sugars. Before your treatment starts, it’s a good idea to contact your diabetes team. This is so they are aware you may need some extra support during your cancer treatment.

If you have lost a lot of weight before starting cancer treatment, the medicines you take to lower your blood sugar may need to be changed. Your diabetes team can give you advice about this.

I was diagnosed with type 2 diabetes just before the cancer. I focused on treating the cancer first, but it became more complicated when I needed surgery.

Clare


Long-term health problems

Diabetes can cause long-term health problems for some people, 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 and make sure you are fit enough to have cancer treatment.

During treatment, you may need to be monitored more closely than people who don't have diabetes. If treatment side effects become very severe, your cancer treatment may need to be adjusted. 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 caused by diabetes.


Controlling your blood sugar

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

While you are having cancer treatment, it is important to try to keep your blood sugar within a safe range. This won’t always be possible, and a slightly high blood sugar isn’t a big problem if it is only for short periods of time. But very high blood sugars should be avoided. They can cause symptoms such as being more thirsty and passing a lot of urine, leading to dehydration. This may increase the risk of developing other problems while you are having cancer treatment, such as infection and poor wound healing. We have more information about managing your blood sugar if you are coping with any side effects of cancer treatment.

High blood sugar levels may also weaken the immune system. This needs to be strong to fight the cancer.

Some people with diabetes are very used to managing their food and medicines. They may not find it difficult to keep their blood sugar levels normal during treatment. But if you have only recently been diagnosed with diabetes, or often have problems controlling your sugar levels, you may need more help. Talk to your diabetes specialist nurse before you start your cancer treatment. They can give you more advice.

Some people with diabetes, especially those with type 2, may not monitor their blood sugar. But everyone with diabetes who is planning cancer treatment should regularly monitor their blood sugar. If you don’t already have monitoring equipment, ask your diabetes team to get you some. They can tell you how to test your blood sugar, how many times to test a day and the sugar level you should be aiming for. You should be given the contact number of a diabetes specialist. You can call them to discuss anything worrying you about your diabetes.


Going into hospital

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

You will usually know when you are going into hospital. This means you can plan ahead 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 and your doctors may need to adjust your diabetes treatment. They will discuss this with you first.

All the ward staff should know that you have diabetes, but it is a good idea to remind them when you first meet. They should also be up-to-date with your diabetes care. If you are not able to give them this information, they can contact your local diabetes team. You may also find it helpful to discuss your care with the hospital’s diabetes team.

Being in hospital and having cancer treatment can make it more difficult to concentrate on your diabetes. It is important to ask the team looking after you for help if you are struggling to control your blood sugar.

Diabetes equipment

When you go into hospital, it is a good idea to take your own diabetes equipment. For example, you might want to take your blood-testing kit, insulin pen, or 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.

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 a similar alternative. But not every ward or unit will have all the different drugs used to treat diabetes, so there can sometimes be a delay getting them.

You may only spend a few hours in hospital at a time, for example if you are having chemotherapy in a day unit. It's a good idea to take a packed lunch and your medicines with you. Try to stick to your normal routine as much as possible.


Tests and scans

Lots of different tests and scans are used to help diagnose cancer. Some of these tests are also used during treatment and as part of your follow-up care. Many of them will not affect your diabetes, but it is a good idea to contact the hospital before the test and tell them that you have diabetes. They can give you advice.

Some tests take a few hours. When you contact the hospital, ask how long you will need to be there. You can then plan ahead so that you have everything you need with you, such as your equipment and some food.

Some tests need a bit more planning. For example, you may need to stop eating for a few hours before some tests. And you may need to have an empty bowel.

The hospital staff will let you know how to prepare for the tests. You may need to go into hospital the day before. You can ask your diabetes team for more advice too.

If your blood sugar level goes too low (below 4 mmol/l) at any time before the tests, you should eat or drink a fast-acting carbohydrate, such as glucose tablets or Lucozade®. It’s a good idea to take some glucose tablets with you when you go to the hospital.

Not eating before a test

You may be asked not to eat for a few hours before some tests, for example before an MRI (magnetic resonance imaging) scan or a CT (computerised tomography) scan. These scans are used to build up a detailed picture of the inside of the body.

Not eating can be a problem for people with diabetes. Because of this, you may be told you cannot eat for a shorter amount of time than people who don't have diabetes.

The hospital staff will give you information about when you can eat and when to take your diabetes medicines. It is important to follow this advice carefully. They should also give you an early morning appointment, to reduce the amount of time you cannot eat.

Having a colonoscopy or barium x-ray

A colonoscopy and a barium x-ray look at the lining of the bowel from the inside. The bowel needs to be completely empty, so you will need to follow a careful diet before the test and won’t be able to eat for a few hours. You will also need to take a laxative.

You will be given information to help you control your blood sugars before, during and after the test. It is important to follow this advice. Contact your diabetes team if you are unsure about the best way to manage your blood sugars.

You should also be given a morning appointment for these tests. This helps to reduce the amount of time you cannot eat and drink. Contact the hospital if you have been given an afternoon appointment, as it may be possible to change the time.

Having a PET scan

A PET scan (positron emission tomography scan) uses low-dose radioactive sugar to measure the activity of cells in different parts of the body. It can be used to find out if a tumour is cancerous or non-cancerous, if it is growing and if it has spread to other parts of the body. A PET scan is often combined with a CT scan.

About two hours before the scan, you will have an injection of a sugary fluid with a small amount of radioactivity in it. The injection is given into a vein, usually in your arm. Cancer cells are usually more active than normal cells, so they take up more of the radioactive sugar. The sugar helps the cancer cells show up on the scan.

How well the PET scan will work depends on how well your diabetes is controlled:

  • If your blood sugar level is high, the cancer cells may not take up much of the radioactive sugar. This is because they already have enough sugar from your blood. If the cancer cells don’t take up the radioactive sugar, they won’t be seen on the scan.
  • If the amount of insulin in your blood is high, your normal cells are encouraged to take up more of the radioactive sugar. This means the cancer cells take up less sugar and don’t show up on the scan as clearly.

Before a PET scan, everyone will have their blood sugar level checked. If the sugar level is too high, the scan may have to be postponed to another day.

Before the day of your PET scan, you should tell the scanning department that you have diabetes. They will give you information about what and when to eat, and which diabetes medicines to take in the days before the scan. The information will also tell you what food and diabetes medicines you should take with you to the hospital. It is important that you follow this advice carefully.

The amount of radioactive sugar you are given is small and it should not affect your diabetes.

Scans using a dye (contrast medium)

Some types of scan involve having an injection of a dye that makes certain areas of the body show up more clearly. The dye is known as a contrast medium. It is used in many different types of scan, including:

  • a CT scan
  • an MRI scan
  • an IVU (intravenous urogram) – a test to look at the urinary system
  • a venogram or an angiogram – tests to look at the blood vessels.

A contrast medium can temporarily affect how your kidneys work. This can be a problem if you take the diabetes medicine metformin. If you take metformin, you will be asked not to take it on the day of your appointment and for about two days afterwards. You will be given information about when you should take it and how to manage your blood sugar during this time.