Understanding Cancer Dual Diagnosis: Diabetes + Cancer

What to Do When You Have Diabetes AND Cancer

Glucose meter and vegetablesMore than 29 million people in the United States are living with diabetes. Of those, 8 million don’t know they have it. An even greater number, 86 million, have a condition called pre-diabetes, which means they are at a very high risk of developing diabetes.

Diabetes: The Basics  
Glucose is a form of sugar that circulates in the bloodstream and provides energy to the organs in your body. The food you eat can be converted into glucose, which is metabolized by your body to sustain its daily activity. 

Your body tightly regulates glucose levels in the blood by secreting insulin, a hormone produced by the pancreas, into the bloodstream. If your blood glucose level stays too high for too long, your body can lose the ability to deliver insulin effectively. This puts you at risk for developing diabetes.

Cancer + Diabetes  
For a person with diabetes, cancer and certain cancer treatments can affect diabetes control. Also, cancer treatments may elevate blood glucose in a person with no previous diabetes, a condition known as secondary diabetes. For example, some immunotherapy drugs, which are used to treat a variety of different cancers, can – albeit rarely – cause Type 1 diabetes, in which the body stops making insulin. 

For a person with diabetes, cancer and certain cancer treatments can affect diabetes control.

You are at higher risk of developing secondary diabetes if you are undergoing chemotherapy treatment, have had your pancreas removed, are using a feeding tube, or are taking high doses of steroids, such as prednisone or dexamethasone. Other factors that can contribute to high blood glucose include the cancer itself, uncontrolled pain, decreased physical activity, and physical or emotional stress.

Signs + Symptoms  People with high blood glucose may experience excessive thirst, frequent urination, blurry vision, and weight loss. If you begin to have these symptoms, you should tell your doctor and have your blood glucose level checked. If you have a history of diabetes, it’s important to check your blood glucose level during chemotherapy and to alert your doctor if you develop these symptoms or if your blood glucose is elevated.


5 Quick Tips for Keeping Your Blood Sugar in Check


Your doctor or nurse can give you more specific recommendations, but adopting these healthy habits can help keep your blood glucose level in check:

• Exercise at least 30 minutes a day.
• Eat plenty of fresh fruits and vegetables.
• Limit your carbohydrate intake.
• Decrease saturated fats in your diet.
• Avoid sugar-sweetened beverages.

Risks + Complications  If you have diabetes and your blood glucose level is not controlled, you are at increased risk of heart attack, stroke, and other complications, such as kidney failure, blindness, amputations, or nervous system damage. If you have secondary diabetes, the short-term increase in blood glucose may not contribute to long-term complications. However, if your blood glucose level is high, your cancer treatment may have to be put on hold until your blood glucose is back under control. Short-term complications of secondary diabetes include infections and dehydration.

Diabetes Treatment, Management, & Monitoring 
If you have diabetes, you should have your cholesterol levels and blood pressure monitored. You should also undergo annual screening for diabetic eye and kidney disease.

Oral medications are available to treat diabetes, but you and your doctor should take into consideration how their side effects might affect your cancer treatment. If your blood glucose level remains high despite the use of oral medications, you may be started on insulin therapy. Some people may need to continue insulin therapy indefinitely to maintain good blood glucose control. 

Your doctor may monitor your diabetes control with the hemoglobin A1c test. This blood test reflects your average blood glucose level over a three-month period. But for some people, including those who have recently received a blood transfusion, this test is not helpful. Therefore, it’s important to learn how to check your blood glucose level at home using a glucose meter. 

Your doctor may advise you to check your glucose level before or after meals, and will use this information to decide if any changes need to be made in your course of treatment. You may also need to adjust your diet and activity level to help manage your blood glucose. 

Managing diabetes while living with cancer can be challenging. It requires coordination and communication among you and the members of your healthcare team. It’s important for you to be aware of how your cancer treatments are affecting your blood sugar. Keeping your diabetes under control is critical to ensuring you receive the best treatment for your cancer. 


Dr. Sonali ThosaniDr. Sonali Thosani is an assistant professor in the Department of Endocrine Neoplasia and Hormonal Disorders at the University of Texas MD Anderson Cancer Center in Houston, TX, with clinical interests in the management of steroid-induced hyperglycemia in people with cancer. 

Dr. Victor LavisDr. Victor Lavis is a professor, also in the Department of Endocrine Neoplasia and Hormonal Disorders at MD Anderson, with clinical interests in the management of diabetes and hyperglycemia in people with cancer.

Visit the American Diabetes Association website, diabetes.org, for more information about managing and monitoring diabetes, along with a variety of diabetes-friendly recipes and other resources.

This article was published in Coping® with Cancer magazine, September/October 2017.