How does having diabetes affect my cancer treatment?

Pictured: Azeez Farooki

Endocrinologist and diabetes expert Azeez Farooki

More than 25 million people in the United States have been diagnosed with diabetes, according to the Centers for Disease Control and Prevention. Among people 65 and older, nearly 27 percent have diabetes.

The vast majority of diabetes cases are type 2 diabetes, which is associated largely with older age and being overweight as well as family history. Older age and obesity also are risk factors for developing cancer, which means that people with type 2 diabetes are diagnosed with cancer more often than those in the general population.

Having diabetes can complicate cancer treatment due to a number of factors.

At the same time, some treatments for cancer, including certain newer targeted therapy drugs, can spur the development of diabetes, especially in patients who already had a propensity toward developing the disease, although this effect is usually reversible.

Azeez Farooki is a Memorial Sloan Kettering endocrinologist who specializes in treating cancer patients who also have diabetes. We spoke with Dr. Farooki about what special considerations are taken into account when treating this group of patients.

A Disease of Blood Sugar

“Diabetes is a disease in which a person has increased levels of glucose, or sugar, in the blood,” Dr. Farooki explains. “It can occur because the pancreas does not produce enough insulin — the hormone that allows glucose to be absorbed — or because cells do not respond to the insulin that is produced. Cells should normally take in sugar from the blood; if they don’t, then high blood sugar or ‘hyperglycemia’ results.”

The majority of people with type 2 diabetes are overweight, which often causes the body to become resistant to the effects of insulin. Type 2 disease may be treated with insulin injections, other hormonal injections, or oral medication. “But the cornerstone of therapy is weight control,” he says, “by staying active, exercising, and carefully controlling the diet, especially by limiting the consumption of simple, low-fiber carbohydrates and sugars.”

The short-term effects of not treating diabetes include frequent urination and severe thirst, fatigue, and recurrent infections. The long-term effects include loss of vision, kidney problems, heart disease, and nerve damage. “Cancer is also an under-appreciated long-term risk resulting from obesity, prediabetes, and type 2 diabetes,” he adds.

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Effects of Chemotherapy

Chemotherapy is a common treatment for cancer patients, but its side effects can make it more difficult to keep blood sugar levels in check.

“Steroids are often given with chemotherapy to lessen nausea,” Dr. Farooki says, “but we know that steroids can raise glucose levels pretty markedly. For this reason, diabetes treatments need to be adjusted, and insulin injections may need to be started, especially around the time that the steroids are given.”

Steroids can also cause diabetes to arise, especially in people who already have risk factors for developing the disease.

For people with diabetes who take injectable insulin, determining the appropriate dose can also be a challenge. “Insulin is generally given before a meal, and that’s done assuming someone’s going to eat a full meal,” Dr. Farooki says. “If a patient throws up or has diarrhea after eating because of their chemotherapy, they may not absorb the food, causing their blood sugar to drop too low.”

Uncontrolled high blood sugar can also cause dehydration, as can vomiting associated with chemotherapy. “Thus, it is important to detect and prevent high blood sugar in this setting,” he says.

In addition, he notes, patients who are not feeling well are more likely to eat so-called comfort foods, which tend to be high in carbohydrates and can negatively affect blood sugar levels.

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Other Complications

Dr. Farooki explains that cancer treatment can be more difficult for people with diabetes, because they tend to have more health problems before beginning their treatments. “Diabetic patients tend to be sicker,” he says. “They have fewer reserves in their body to be able to fight against the various complications that may come up, such as infections.”

New targeted cancer therapies offer treatment options for some patients, and these drugs generally cause fewer side effects than traditional chemotherapy. Nonetheless, several targeted drugs do affect blood sugar levels.

Dr. Farooki was part of a National Cancer Institute–sponsored task force that looked at this issue. The recommendations of the task force were published in the Journal of Clinical Oncology in 2012.

He explains that in patients who didn’t previously have problems, blood sugar levels usually return to normal after treatment with these drugs has been completed, but that existing diabetes can be a barrier to starting these drugs, especially in patients who are participating in clinical trials with strict entry requirements.

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Treatment Decisions

Dr. Farooki notes that especially for patients whose cancer is advanced, controlling glycemic levels to the very strict levels aimed for in patients without cancer does not always need to be prioritized. “For these patients, the primary and immediate focus is on treating the cancer,” he says.

“You don’t want to deprive them of a potentially life-sustaining drug because you are concerned about their blood sugar being marginally high. However, we want to avoid very high blood sugars that can predispose to immediate symptoms such as frequent urination, dehydration, unintentional weight loss, and infection,” he adds. “But the long-term effects of high blood sugar are of lesser concern. With advanced cancer, we’ve got bigger fish to fry.”

Some research raises the possibility that using insulin itself to correct hyperglycemia may curtail cancer growth and progression. “Both diabetes and cancer are considered inflammatory diseases, and involve inflammation at the cellular level,” he says. “It’s possible that preventing hyperglycemia with insulin may have antiinflammatory and antiangiogenic properties.”

Inflammation has long been associated with the development of cancer; blocking angiogenesis, the process by which tumors increase their blood supply in order to grow and spread, is a current focus of many cancer researchers.

On the other hand, since insulin is a growth factor, it has long been debated whether large doses of insulin could stimulate cancer growth.

In addition, some studies have indicated that metformin, an oral drug commonly used to treat diabetes, may provide oncologic benefits. “There’s a lot of interest right now in studying this,” he says.

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Commenting is disabled for this blog post.

Very truly said.Thanks a lot Dr.Farooki

My mother is has stage 4 cancer do chemo what can she eat it everything makes hr sugar shot up high , the cancer doctor tells her to eat has much as possible an she cant eat much because everything raises her sugar

Angie, we’re sorry to hear your mother is having these problems. We are not able to provide medical advice on our blog, but we recommend that you or your mother talk to her doctor more about this. The doctor may be able to provide you with some more guidance or refer you to a specialist if needed. If you’d like to make an appointment to speak to someone at MSK, you can call 800-525-2225 or go to for more information. Thank you for your comment.

I am very worried because I was recently diagnosed to have ductal carcinoma. I had a lumpectomy(1.6 size) with no nodal involvement. I am a diabetic using insulin with an A1C of 7.3. I am obese. I have sleep apnea, poor venous return, and some problems with urination. I need to have chemo because of tumor size and a positive HER2. Please give me some information that might help me feel more secure of these 12 treatment that I need to have followed by 9 months of Herceptin every 3 weeks. Please help me.

Sandy, unfortunately we are not able to provide individual medical advice on our blog. We recommend that you speak with your oncologist about your concerns. If you’d like to make an appointment to speak with a physician at Memorial Sloan Kettering, you can call 800-525-2225 or go to for more information. Thank you for your comment.

my friend was stuck by a diabetic needle at work patient also recently diagnosed with cancer my question is can he get cancer from this

Mary, if your friend is concerned about contracting any kind of infectious agent from a needle stick, she should speak with her supervisor at work. Thank you for your comment.

Youtube Vernon Johnston baking soda and molasses cancer protocol. It is very interesting. Also checkout the reviews. Again quite interesting.

I am an 84 yr. old male. I was diagnosed with type 2 diabetes 7 yrs. ago and have been taking 5 mg. of glipizide twice a day with good success. However, several weeks ago I was diagnosed with CLL and am now taking 420 mg. of Ibrutinib once a day and my glucose is averaging about 25 points above what it was before. I wonder if I increased my glipizide about 50 percent if that would be a problem.

Ralph, we are not able to answer personal medical questions on our blog. This is something you should discuss with your healthcare team. If you’d like to make an appointment at MSK, you can call 800-525-2225 or go to for more information. Thank you for your comment.

Hi I need your valuble suggesion , As my Mother undergoing chemotherpy (Paclitaxol) Before Last chemo dose, blood report showed blood sugar level high. I read that during chemo it may raise but how to set diet which will lower down sugar level. Thank You

Vijaykumar, unfortunately we are unable to answer specific medical questions on our blog. If you would like to make an appointment with a Memorial Sloan Kettering physician, please call our Physician Referral Service at 800-525-2225 or go to Thanks for your comment.

What foods do you suggest that might fill the "comfort food" desire and help with nausea from the chemo yet keep sugar levels in line?

Tommy, thank you for reaching out. We consulted with MSK dietitian nutritionist Cara Anselmo, and she responds: “Some suggestions are ginger tea, plain yogurt, or fresh fruit. But keep in mind, if you’re not feeling physically hungry, and it’s more comfort than food you are craving, try self-soothing without food. Calling a friend, listening to pleasant music or podcasts, or a doing a simple meditation might be more helpful than anything you could eat.”

Hi my mom diagnosed with stage 2 cancer. Has diabetes and is recovered stroke patient. Should she do chemo or what alternative therapies do u suggest. Also if she does have chemo what diet would be good For her. She is 66.


Ami, we are not able to offer medical advice on our blog. This is something your mother should discuss with her healthcare team. If she’d like to make an appointment for a consultation with someone at MSK, she can call 800-525-2225 or go to for more information. Thank you for your comment.

Thanks what is the best recommend diet she could follow post and pre chemo treatment.

Ami, your mother should speak with a dietitian who has experience working with diabetic patients. Her doctor should be able to recommend someone. Thanks for your comment.

I am a diabetic 62 year old. I have had breast cancer 20 years ago. I am now diagnosed with breast cancer. The lump is under the nipple. Do I need to have a mastectomy?

My aunt 60, has been operated for removal her cancerous breast, She is a Type 2 diabetic and was on insulin. After surgery she has been given first dose of Chemo. since the first dose of chemo, she is experiencing unbearable pain while injecting insulin. The injecting points are becoming red and imflamation is setting. Even one such spot has developed infection.

We are sorry to hear about your aunt’s experience with pain and infection. These issues should be brought to the attention of her doctor, who can help address these issues.

My father has been diagnosed with mouth cancer stage 4. They treatment is not started as yet but the doctor said that it has not spread out anywhere and they'll operation ASAP but my father is a diabetic patient. What can he eat because everything he eats shoots his sugar high. Please suggest

Thank you for your comment. We recommend that you or your father talk to his doctor more about appropriate foods to eat. The doctor may be able to provide you with some more guidance or refer you to a specialist if needed. If you’d like to make an appointment to speak to someone at MSK, you can call 800-525-2225 or go to for more information. Thank you for your comment.

Hi, I was diagnose with colon cancer in the descending area of my colon. I am type 2 diabetic I am having the surgery to removed the mask form my intestine in a few days we will know about the lymphoid if they have been affected. I know their are different types of chemotherapy what is normal the best for for diabetic type 2 patients.

Thank you for your comment. Unfortunately, we are not able to offer medical advice on our blog. This is something you should discuss with your healthcare team. If you would like to make an appointment for a consultation with someone at MSK, you can call 800-525-2225 or go to for more information.

To learn more about the treatment of colorectal cancer at Memorial Sloan Kettering, you can go to:

Hi.. im diagnose with leukemia(ALL) currently under chemo for 3rd cycle now.. the doctor told me im having slight rise in blood sugar level.. is it normal?

Hi Wan, we recommend you discuss this with your oncologist. Thank you for your comment.

Your article states that steroids given during chemotherapy can also cause diabetes to arise. Does this mean it could arise during chemo treatment, or could it also arise some time after treatment is completed?

Hi Paul, we sent your question to Dr. Farooki, who responded, “If the blood sugar is going to go up, it would be at the time that the steroids are given. This usually occurs during chemotherapy.” Thank you for your comment.

dad going thru chemo and radiation for bladder cancer. he is also diabetic and takes novolog and levimir. blood sugar has dropped to 26 after radiation one day and 68 after another radiation treatment. any correlation between radiation and drop in blood sugar to dangerous levels?

Dear Patty, we’re sorry to hear your father is going through this. We recommend that you and he discuss these issues with his oncologist and his endocrinologist. Thank you for your comment, and best wishes to you.

My wife just started getting chemo four days ago and she can't get her blood sugar levels down in the normal range my question do the chemo drugs Cisplatin and Gemzar render the insulin that she injects to be ineffective to lower her blood sugar levels??? Her readings have been as high as 460 and she has taken enough regular insulin since Saturday that would have killed her by now and she has not been eating that much to make her levels go that high. I guess what I am asking is does the chemo drugs kill the insulin ???

Dear Alec, we’re sorry to hear your wife is going through this. We recommend you discuss this situation with her oncologist and her endocrinologist. Thank you for your comment, and best wishes to you.

My father was just diagnosed with stage III colon CA. He is a brittle diabetic. HX of retinopathy, neuropathy, right leg amputation r/t ostemylitis, lymphadema in left leg, CHF and some dcline in renal function. What will chemo likely do to his eyes and his remaining leg?

Dear Andrea, we’re sorry to hear about your father’s health problems. Unfortunately, we aren’t able to answer medical questions on our blog. We recommend that you discuss this with his healthcare team. If he is interested in coming to MSK for a consultation, you can call 800-525-2225 or go to for more information on making an appointment. Thank you for your comment, and best wishes to you and your family.

Just a comment to all those doctors and clinics, recently i was diagnosed with high platelets and referred to an oncology center with no information other than high numbers. Here 3 weeks later and still no appointments, called and gotten voice mails. In the meantime I am worried sick and wonder how far whatever is wrong with me can go waiting for an appointment or a call back.

I found your article on Diabetes and Cancer Treatment very informative. As it was written in 2013, I am curious whether there has been any addtional findings or new opinions on the subject. My husband had stage 1-B pancreatic cancer. Half of his pancreas was removed and he is cancer free. We are about to embark an agressive preventative treatment to make sure it does not return. Not asking for advice. However, since my husband is a diabetic who is having a very hard time keeping his numbers down; I am very interested in being as informed as possible. Thank you

Dear Debbie, we’re sorry to hear about your husband’s diagnosis but glad to hear that he is now cancer free. Cancer and diabetes is an active area of research at many centers. For the latest updates, we recommend you contact the National Cancer Institute’s Cancer Information Service at 800-4CANCER. Thank you for your comment, and best wishes to you and your husband.

hello my dad has prostate cancer that has spread from his lungs to his feet but we have just found out that his has diabetes an not sure what gonna happen now well still be able to out from this

My mum is diabetic and has stage 4 liver cancer,why has her insulin been dropped from 56units to 27 units per day.

Dear Margaret, we recommend that you discuss this with your mother’s healthcare team. Thank you for your comment, and best wishes to both of you.

my bestfriend has type 2 diabetes and now she has been diagnosed with throat cancer she is loosing her voice and she is only 17 years old i just want to know any details

Dear Kimberly, we’re very sorry to hear about your friend. We recommend that you discuss your concerns with your friend and her parents. Thank you for your comment, and best wishes to you.

I was diagnosed with type diabetes in May 2016. Been on various drugs. Metformin was the only drug that did not give me adverse side effects. Then in October 2017, I started seeing Dr Eric Westman from Duke. In 10 weeks he was able to reverse my a1C from 8.3 to 6.4. Essentially reversing my diabetes, putting me into pre-diabetic. Then it took me 6 months to lower my glucose using a finger prick to under 100. Reversing my preidiabetes. That I received permission to stop taking Metformin. Resulting in my blood sugars rising to 170. Then using the tools I taught myself ( from Dr Westman and Dr Jason Fung) lowered my sugars to 120 in three hours. I have read the studies linking taking metformin to reduce the incidence of developing cancer against those diabetics not taking metformin. Have also read the studies demonstrating an increase likely hood of developing cancer as a diabetic against an healthy person. I can count myself as a healthy person today, an non diabetic, just by following the Keto diet for 10 weeks. Then using Keto and intermittent fasting to reverse my pre-diabetes

I have just completed my radiation for breast cancer. In my final week of radiation I developed pneumonia. I was given IM Rocephin, Levoquin, and a steroid injection. In the same week I had labs drawn. My A1C came back 8 and my triglycerides were 497. I have never had these high levels. Could this illness and radiation contributed to my high lab values ?

Dear Patty, we’re very sorry to hear about what you’ve been through. We recommend that you discuss this with your medical team, since they are familiar with all the treatments that you’ve had as well as your medical history. Thank you for your comment, and best wishes to you.

Do you have any referrals for England, particularly the Liverpool/Manchester area. I will be care giver for family member Type 2 diabetes and uterine cancer. They are leaning towards radiation rather than chemo. I am concerned about maintaining blood sugar levels while dealing with the potential nausea, lack of appetite.