Steroids (sometimes called corticosteroids) can be used for cancer treatment. They can also help to manage some side effects of some chemotherapy drugs or improve your appetite.
Steroids can increase blood sugar levels in people who have diabetes. It can also increase blood sugar levels in people who do not have diabetes. This can happen because:
- the liver produces more sugar during steroid treatment
- steroids make it harder for sugar to move out of the blood
- your body may become resistant to insulin while you are taking steroids.
You may find it more difficult to control your blood sugar level when you are taking steroids. How your blood sugar is affected will depend on:
- the type of diabetes you have
- how you normally manage your diabetes
- which steroids you are taking
- how you are taking the steroids – your blood sugar may start to increase a day or two after taking steroid tablets, but could increase a few hours after having a steroid injection
- the dose of steroids – the higher the dose, the more likely your blood sugar will increase
- the time of day you take the steroids
- how long you are taking the steroids for.
If you do not have diabetes, a rise in your blood sugar level is called steroid-induced diabetes.
Tell your cancer doctor or specialist nurse if you feel unwell or develop any of the symptoms of diabetes. These could include:
- being really thirsty
- having blurred vision
- passing a lot of urine (pee)
- feeling very tired.
If you are at risk of developing diabetes, they may ask you to monitor your blood sugar level while you are taking steroids.
Your blood sugar level may go back to normal when you stop taking steroids. Some people may need to start treatment to help control their blood sugar. Your cancer doctor or specialist nurse will talk to you about this.
Sometimes steroids used to treat cancer can lead to permanent diabetes in people who were already at risk of developing diabetes. The blood sugars may reduce once you stop taking the steroids, but the diabetes may still need treatment. This is called steroid-induced diabetes and is like type 2 diabetes.
You can find out more about diabetes, diabetes symptoms and risk factors for diabetes at Diabetes UK.
Before you start taking any steroids, talk to your doctors about how to keep your blood sugar within your target range.
Checking your blood sugar
If you have diabetes, it is very important that your blood sugar level is tested during steroid treatment. If you do not already check your blood sugar, you will need to start checking it. If you do, you will need to check it more often. When you first take the steroids, make sure you have enough blood-testing equipment with you at home.
Your doctor may also suggest you check your blood or urine for ketones. Ketones are chemicals that can sometimes build up in the body when there is a severe lack of insulin. Ketones are toxic to the body and large amounts can be very serious. A high level of ketones in the body is called diabetic ketoacidosis (DKA). It mainly affects people with type 1 diabetes, but it can affect anyone with diabetes who uses insulin. It can also affect people who control their diabetes with tablets and their diet, but this is rare.
You should keep a record of your blood sugar levels and when you take the steroids. This is so you can see if there is a pattern. You can share the record with your doctors and nurses.
If your blood sugar is high
You should talk to your cancer doctor, diabetes team or your GP as soon as possible if:
- your blood sugar levels are high (more than 15 mmol/l) on more than 2 or 3 occasions
- you feel unwell or develop any of the symptoms of diabetes, such as being really thirsty, having blurred vision, passing a lot of urine or feeling very tired.
If your blood sugar level stays high while you are taking steroids, your cancer doctor or specialist nurse may change the dose. They may also change the time you take the steroids. They may spread the dose out during the day.
Changing your diabetes treatment
You may need to change the way you control your diabetes:
- If you use your diet to control your diabetes, you may need to start taking tablets to control your blood sugar.
- If you already take tablets, you may need to increase the dose or start using insulin for a short time.
- If you already use insulin, you may need to increase the dose or use a different type of insulin.
Correction doses of insulin can be used to reduce very high blood sugars. These may not work as well when you are taking steroids. Your diabetes team can give you advice. They may suggest you take more insulin.
You should never stop taking your steroids without talking to your cancer doctor first.
The dose of steroids you take as part of your cancer treatment will usually be reduced and stopped. Ask your cancer doctor or specialist nurse, so you can change your diabetes treatment as this happens.
Some people may need to continue to take a small dose of steroids for a long time. Your diabetes team can help you manage your blood sugar during this time.