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What to Do When It’s Diabetes and Cancer

18 Minutes Read

Navigating cancer is especially challenging for people with diabetes. Learn how cancer treatments can affect diabetes management in many ways, from blood sugar levels to food sensitivities to exercise and more.

Just found out you or a loved one has been diagnosed with cancer while already living with type 1 or type 2 diabetes?


That’s the first piece of advice from Joe Trotter, a nurse clinician and certified diabetes care and education specialist with the Emory Clinic in Atlanta. Trotter, 46, has lived with type 1 diabetes for 20 years and was recently diagnosed for the second time with early-stage renal cell carcinoma, a form of kidney cancer.

“You can’t tell people not to feel stress or to feel angry or sad” when they first hear they have cancer, said Trotter. “Those are valid, and you should feel how you feel. Try to stay calm and don’t stop taking your medications. Find out what your treatment plan is, if it could affect your blood sugar, and how your regimen might need to change.”

Navigating a cancer diagnosis when you already live with diabetes involves understanding and dealing with a host of new factors that can affect how you feel, how your blood glucose levels react, and can cause anxiety and fear. But Trotter and other experts we spoke with – both healthcare professionals and people with diabetes who have dealt with cancer – offer the following advice on how to best handle the challenge.

Talk to your team

Ensure you have a team of medical professionals overseeing your care that you trust. This can include an oncologist to manage your cancer treatment, as well as an endocrinologist, certified diabetes care and education specialist (CDCES), or insulin pump trainer (if you use a pump) to oversee your diabetes care. You should also call on others, seeking mental health and nutrition support that your cancer facility may offer.

The team approach is what Nicola Perkins, 35, advises. She was diagnosed with breast cancer in January 2020, underwent 12 weekly sessions of chemotherapy, and took Herceptin every three weeks for a year as part of a chemotherapy that targeted cancer cells to try to slow or stop their growth. She also had a bilateral mastectomy that year and expects to have two or three more surgeries and another six months of active treatment. She has lived with type 1 diabetes for 19 years and wears an insulin pump and continuous glucose monitor (CGM).

“A cancer diagnosis is scary,” she said. “One of the first things I did was call my endocrinologist and pump trainer. I wanted all the help I could get to be able to manage my diabetes throughout chemotherapy and surgeries.” Her oncologist would adjust her medications before starting chemotherapy. “I knew my glucose levels would run higher the day I started steroid medication, until about two days after chemo, so during that time I used my insulin pump in manual mode, rather than in closed loop.” Doing this allowed her to maintain a 5.1% A1C during treatment.

People with diabetes who are diagnosed with cancer and who are already doing what they can to manage their blood glucose levels tend to have better outcomes than those who are not as well-managed, said Dr. Sonali Thosani, associate professor at MD Anderson Cancer Center in Houston. Those who have a tougher time managing blood glucose levels, however, are more likely to have issues during cancer treatment, such as poor wound healing, higher mortality rates, and postponed treatments.

“There could even be a delay in surgery until an A1C is lower,” Dr. Thosani said. “It makes the overall treatment more challenging.”

Treatments and medication management

Unfortunately, diabetes can’t take a back seat to the new cancer diagnosis, said Chris Memering, a nurse and inpatient diabetes care and education specialist at CarolinaEast Health System in New Bern, North Carolina. It’s just as important, if not more so, to stay on top of your diabetes care at this time, particularly because different cancer treatments may involve medications that can affect blood sugar levels, appetite, or your level of activity.

“One of the big things when you start cancer treatment is to test your blood sugars as often as you did before the diagnosis, and potentially more often,” said Memering. This can be easier for people with type 1 diabetes because they often test 4-12 times a day or have continuous glucose monitoring (CGM) technology. People with type 2 diabetes may be testing as little as once a day.

Without ongoing testing, or CGM use, “if people are on steroids, blood sugars may rise dramatically, and people can end up in the hospital because they didn’t know to test,” Memering said. “Anytime people are put on steroids, there is a need to check blood sugar levels more often, but sometimes that information doesn’t get communicated fully.”

Steroids are used to help kill and shrink cancer cells alongside chemotherapy. They also help reduce swelling, nausea, allergic reactions, and headaches from brain tumors. If you are prescribed steroids to help with your cancer treatment, ask your oncologist what medications you will be taking and how they may affect your blood glucose levels.

Still other types of cancer medications can lead to different issues, such as causing people with type 2 diabetes to permanently require insulin, said Dr. Thosani. Radiation, another form of cancer treatment, can cause changes in appetite (depending on the site of radiation) that could affect glucose management.

It is highly recommended to keep a journal or chart of your treatments, medications, side effects, glucose responses, and other outcomes. Because most chemotherapy is delivered in cycles, having data points and a log to refer to as your cancer treatment progresses will help you discuss your diabetes management with your care team. It may also help you avoid facing some of the same challenges over and over again.

Food sensitivities

Food and weight are complicated when cancer is involved.

With a cancer diagnosis, for people with diabetes and obesity “we ask them to try to lose weight, but to be careful not to lose muscle mass,” Dr. Thosani said. “Obesity increases the risk of multiple cancers, so we encourage weight loss during treatment through healthy lifestyle changes. Weight loss can also help improve glucose management, which in turn reduces risk of infection or dehydration – hyperglycemia can cause dehydration which can lead to increased toxicity from chemotherapy.”

Obesity has also been linked to higher rates of cancer recurrence and complications such as blood clots, cancer-related fatigue, and surgical complications such as infections, according to Cancer Today magazine. However, losing muscle mass can weaken a person, and “we can’t give chemotherapy to those who are weak. It can also increase the toxicity of the chemotherapy. An oncologist doesn’t want a patient to lose too much weight too quickly, as it can affect how well they will tolerate the chemotherapy,” said Dr. Thosani.

Weight loss also affects how much insulin is needed – typically, this means less is needed, said Memering. “We remind people that if you have experienced a 10 percent weight loss, you usually need to adjust your insulin doses accordingly,” she said.

Cancer treatments might also affect what foods people should eat or want to eat. Depending on the cancer diagnosis, some people will need a stem-cell transplant to help restore blood stem cells that have been destroyed through chemotherapy or radiation treatment, according to the National Cancer Institute. After a transplant, people may not be able to eat certain types of foods, such as fresh fruits or vegetables, because the body’s ability to fight off infection may be impaired, and avoiding such foods lowers the risk of contracting a foodborne illness. Cancer treatments may also affect foods’ flavors – making them taste metallic or as if they had no taste at all. Nausea can also occur.

“People may have a change in their taste buds, and sometimes, the foods that taste good are not necessarily helpful for diabetes management,” said Dr. Thosani.

Because of these restrictions and changes, working with a dietitian is important to figure out what foods can be eaten and tolerated safely, said Memering. Nutrition and diet have been shown to play a major role in successful cancer outcomes, so lean on the resources available, especially if your cancer center provides nutritional counseling.

Exercise: what to expect with cancer

Many people undergoing cancer treatments experience “a tremendous amount of cancer fatigue, and many people find they cannot really exercise, or people who did regular exercise before may find it particularly difficult to do their regular routine,” said Dr. Thosani. “We encourage walking, because it helps with both diabetes and cancer.”

Endurance may also be different during cancer treatment, but “if you’ve been active, exercise is something we encourage you to continue,” said Memering. “It may be that the day after treatment you can’t be active, but know if you continue to get out there and it makes you feel good, we want you to get out there. The more you exercise, the more your body wants it and the easier it is to do.”

Evaluating glucose trends

Using a CGM can be very helpful for all people with diabetes and cancer, said Dr. Thosani, who noted that the wide availability of CGM makes it easier for people with type 2 diabetes to begin using a CGM if they hadn’t already before their cancer diagnosis.

The blood glucose trends are valuable for feeling better during cancer treatment, said Memering. “People look at the numbers as judgment; I look at it as data,” she said. “I am there to try to figure out how this affects your quality of life, which can be fine or really bad. I’m trying to find a way to help you that may make it better. One of the ways to do that is to take a little time to understand your diabetes so you aren’t so tired because your blood glucose is really high, or you are low all the time because you can’t eat.”

Taking care of mental health

“Mental health challenges come up in all parts of new diagnoses and chronic disease management,” said Memering. “There can be a high mental burden for those with diabetes, and anyone receiving a cancer diagnosis may go through the five stages of grief: denial, anger, bargaining, depression, and acceptance. The coping strategies that people have used in their diabetes management may need to be called upon when planning and facing treatments for cancer.”

Depending on where you are receiving treatment for your cancer, many oncology centers have a team therapist, psychologist, or psychiatrist. If you’re newly diagnosed, that person may be assigned to you, but if not, “asking for this referral is absolutely appropriate and encouraged,” said Memering.

“I encourage the people with diabetes that I see to understand that their mental health plays greatly into their physical health,” she said, “and I recommend seeing a mental health professional who may specialize in the needs of those with chronic disease.”

Finding support from your healthcare team, family, and friends can help you get through a cancer diagnosis while also managing your diabetes. Connecting with others who have diabetes and cancer may prove helpful. Ask your oncologist or mental health professional about support groups; some are geared specifically to different types of cancer.

Here are some online resources that may be helpful:

A cancer diagnosis can feel devastating and overwhelming, and your diabetes diagnosis may have felt similar, notes Memering.

“Think about the skills you’ve learned to help you manage your diabetes,” said Memering. “These are likely some of the same skills you need now. Remember, you aren’t a burden to your friends, family, and care team because of this new diagnosis. We want to be there for you and help you through your journey.”

Dr. Thosani urges people to focus on what they can. “I would advise patients with diabetes and cancer to not lose hope,” she said. “Just like diabetes, there have been tremendous strides made in cancer care and treatment, allowing people with cancer to live ‘normal’ lives. Your healthcare team is aware of the unique challenges you face with diabetes and cancer and they are here to help you set personalized targets for your diabetes management while you navigate your cancer treatment.”

Diabetes and cancer: How to lower the odds

People with diabetes – both type 1 and type 2 – seem to have a higher incidence of developing certain cancers, including liver, pancreatic, endometrium, colon and rectal, breast and bladder, said Memering. A study published just this week found cancer to be a leading cause of death among people with diabetes. This is likely linked to person’s age, diet, body weight, and activity level, especially for type 2 diabetes, according to the American Diabetes Association’s webpage on diabetes and cancer. To counter the increased risk, do what you can to try to prevent cancer by not smoking, eating a healthy diet of vegetables, fruits, whole grains, and heart healthy fats, and exercising at least 30 minutes a day, five days per week. A diabetes care and education specialist can also help you find ways to better manage your condition while improving your quality of life.