Diabetes and Cancer: What Is the Relationship?

Having diabetes may raise your risk of cancer. Having both diabetes and cancer can complicate treatment for these conditions. Diabetes is marked by elevated blood sugar levels, and cancer treatment can also affect blood sugar. Adjusting your diabetes medication (including insulin) and food intake may be needed.

This article discusses the connection between diabetes and cancer, including how diabetes affects cancer risk and how to treat and manage the two conditions effectively at the same time.

A Black woman with gray hair and a healthcare provider looking at an insulin pen

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Connection Between Diabetes and Cancer

With diabetes, your body either does not make sufficient insulin or doesn't use it properly to help keep blood sugar levels down. When trying to manage diabetes at the same time as cancer, it can be difficult for several reasons, such as:

  • Cancer treatment can cause blood sugar levels to fluctuate.
  • Diabetes-related health issues may worsen due to cancer-related treatment.
  • Side effects from cancer may be more severe in those with diabetes, with the need for hospitalization more likely.


If you have diabetes, you may be at increased risk for developing certain types of tumors, including the following:

People with diabetes are prone to high blood sugar, high insulin amounts, increased insulin-like growth factor levels, heightened inflammation, and lipid imbalance, which can contribute to increased cancer risk.

High Insulin Concentrations

Researchers think that the pancreas and the liver may be vulnerable to developing tumors because they are exposed to high insulin concentrations in people with diabetes. Studies have shown that elevated insulin levels can indicate if you are at risk for bladder, colorectal, endometrial, pancreatic, and postmenopausal breast cancer.

The theory is that too much insulin or insulin growth factors stimulate cancer cells to develop. Some researchers believe that insulin may actually be a source of energy that fuels cancer cells as it allows more glucose to enter the cells.

It's important to note that if someone has recently been diagnosed with diabetes due to insulin resistance, that can be an early sign of pancreatic cancer and should be checked out.


In some cases, obesity, which is a known risk factor for diabetes, may also play a role in cancer development. The increased fat stores in obesity are associated with raised estrogen levels, which can be associated with greater cancer risk.

Obesity also increases growth factors, chronic inflammation, and reactive oxygen species (unstable molecules that contain oxygen). All of these can damage cells and potentially lead to cancer growth.

High Blood Sugar

There's also the question of raised blood sugar levels (glucose) and how this may be linked to cancer. Too much sugar may produce unstable molecules known as free radicals, damaging DNA and leading to cancerous mutations. Some researchers theorize that blood sugar may offer energy to spur cancer growth. 

Treatment and Management of Diabetes With Cancer

You be more prone to cancer if you have diabetes, and undergoing cancer treatment may affect your blood sugar levels. The effect this has will depend partly on the treatment you are receiving. So, your oncologist (cancer specialist) must take this into account.

Here's how different types of cancer treatment can affect your sugar levels:

  • Undergoing certain types of chemotherapy can cause high blood sugar to occur. Agents that may be associated with such increased levels include Elspar (asparaginase), Busulfex (busulfan), Adrucil (5-FU), and platinum-derived chemotherapy.
  • Hormonal agents given to either block or increase hormone levels, particularly in prostate or breast cancer, can, at times, ramp up blood sugar levels.
  • Some immunotherapy drugs, such as Keytruda (pembrolizumab) or Opdivo (nivolumab), which block the protein PD 1, have been known to cause an increase in blood sugar.
  • Unfortunately, receiving steroids to treat cancer or combat pain and nausea can increase insulin resistance. To help keep sugar levels more stable, you may be given the steroids in smaller doses or more slowly with intravenous injection.
  • Being prescribed targeted therapy can have an impact on how insulin is used. These drugs may include substances that block pathways key to the body's use of insulin. These medications include as Afinitor (everolimus), Zortress (everolimus), and Tasigna (nilotinib).

Having diabetes complicates cancer treatment.

Steroids are a common remedy for nausea associated with cancer treatment or used to treat the cancer itself, but they are known to raise blood sugar levels. You may need to pay particular attention to when the steroids are given and adjust any insulin injections accordingly.

But even that can be challenging. You commonly take insulin before you eat to compensate for the food you plan to consume. But if you're nauseous, you may not be able to consume all you were planning, throwing your blood sugar levels off.

You may also have to be monitored closely for dehydration, which can occur when your blood sugar levels are uncontrolled, or you've been vomiting excessively from chemotherapy treatment.  

If you're undergoing surgery for cancer, your oncologist will want to ensure that your blood sugar levels are well controlled since wound healing will be considerably slowed if this is too high.  

Remember that while your oncologist will consider your diabetes, they will not always prioritize this. Instead, even if it may throw your sugar levels somewhat off, they will still give you needed cancer treatment.


If there is a silver lining here, it is that both diabetes and cancer share some risk factors. It is possible to address some of these and impact both conditions. Some factors that you can control include:

  • Losing weight: Excess weight can increase the possibility that you will develop type 2 diabetes and also increase the risk of some types of cancer. However, by counting calories and opting for healthy food choices, you may be able to head off one or both conditions.
  • Quitting smoking: Smoking cigarettes is linked to cancer and type 2 diabetes. Quitting, however, may take more than willpower. In addition to setting a date, it may be prudent to come armed with a strategy such as nicotine patches or hypnosis.
  • Limit alcohol use: Having just one drink a day if you're a woman or two if you're a man ups your risk of diabetes and cancer. Opting not to drink alcohol or drink it rarely can be an advantage for both.
  • Get moving: Active people tend to have lower levels of cancer and type 2 diabetes. Aim to exercise around five days a week. This can entail something other than heavy lifting. Simply walking regularly can be beneficial.


Having diabetes can put you at risk of having cancer. This may be due to high insulin or blood sugar levels, obesity, or other related factors.

Managing diabetes together with cancer brings its own set of complications. Both cancer itself and the treatment for this can affect sugar levels. Some treatments can cause sugar levels to rise, while others can increase insulin resistance.

Timing for administering insulin may become tricky if nausea and vomiting affect eating. Even if your sugar levels are affected by the cancer treatment, the cancer treatment will take priority. Several of the same lifestyle factors can help ward off type two diabetes and cancer.

A Word From Verywell

If you are contending with both a diagnosis of diabetes and cancer, it can seem overwhelming. The good news is that your oncologist will know how to modify treatment to combat cancer best and keep your sugar levels in check.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Maxine Lipner
Maxine Lipner is a long-time health and medical writer with over 30 years of experience covering ophthalmology, oncology, and general health and wellness.