How to manage blood sugar during chemotherapy

Change insulin medication

If people already use insulin, a doctor may change the dosage or type of insulin they use during chemotherapy. People with diabetes who do not use insulin may need to start using it because their blood sugar levels are likely to increase during cancer treatments.

People may inject insulin using a pen, pump, or syringe.

Manage nausea

Eating meals at regular times and avoiding skipping meals can help someone manage their blood sugar. However, this may be challenging if chemotherapy causes nausea.

If someone has nausea, they can talk with their healthcare team about possible solutions. Anti-nausea medications can help treat nausea and vomiting and may prevent or relieve symptoms before they cause issues.

The following tips may also help people manage nausea and eat regular meals while undergoing chemotherapy:

• Eat 5 or 6 smaller meals throughout the day.
• Avoid foods with strong odors, as well as greasy, fried, and spicy foods.
• If possible, create a relaxing environment for eating.
• Keep track of foods and symptoms to help identify nausea triggers.
• Practice relaxation techniques such as deep breathing.
• Talk with a doctor about acupuncture and acupressure, which stimulate specific points in the body and may help relieve nausea.

Stay well hydrated

Not drinking enough water can contribute to high blood sugar, and having high blood sugar can lead to dehydration by increasing urination. For these reasons, it is important to stay properly hydrated during chemotherapy treatment.

Water contains no calories or carbohydrates, so it will not increase blood sugar levels. People may need to drink more water on hot days or if they feel thirsty.

Adding a slice of fruit for flavor and drinking water first thing in the morning or before meals may help people increase their water intake.

Stay physically active

According to the American Diabetes Association (ADA), exercise increases insulin sensitivity, which improves the way the cells in the body use insulin to take up sugar from the blood.

Muscle contractions during physical activity also cause cells to take up sugar and use it for energy, regardless of insulin availability.

The Centers for Disease Control and Prevention (CDC) suggests that people aim to get 150 minutes of moderate exercise every week. However, people who are undergoing chemotherapy may experience side effects that make it challenging for them to exercise that much.

People could break up that goal and aim for 30 minutes of activity most days, but if this feels like too much, even a 10-minute walk each day can help. A person can talk with their healthcare team about tips for staying physically active during chemotherapy treatment.

The ADA highlights that people who use insulin may need to adjust their dosage or carbohydrate intake to prevent low blood sugar when exercising.

Manage carbohydrate intake

People should monitor their carbohydrate intake when managing their blood sugar levels. Carbs can raise blood sugar levels as the body breaks them down into sugar.

The amount of carbohydrates someone needs to eat to stay in their target blood sugar range will vary from person to person, so people should discuss carbohydrate intake with their healthcare team.

One serving of carbs is usually around 15 grams. Here are some examples of one serving of carbs:

• 2 slices of light, reduced calorie bread
• 1/4 of a large bagel
• 1/3 cup of cooked pasta
• 1 cup of cooked squash
• 6 saltines
• 1 small apple
• 1 cup of milk
• 3 pieces of hard candy

Talk with an oncology dietitian

People can talk with a dietitian who works with people who have cancer and those who are undergoing cancer treatments. A dietitian may be able to help a person:

• cope with changes in taste and appetite
• manage their weight as needed
• find ways to effectively manage blood sugar within their diet

Check blood sugar levels regularly

If a person has high blood sugar, it is important that they check their levels throughout the day. A person can talk with their doctor about getting a blood sugar monitor if they do not already use one. A doctor can explain how and when to use the device.

A doctor may recommend checking blood sugar levels every morning before eating. People may also check their levels after meals and before bed.

Monitoring blood sugar regularly is an important part of managing blood sugar levels. It can help people find out what causes their blood sugar to go up or down and help them stay within their target ranges.

Regular blood sugar monitoring also lets doctors know whether a treatment plan is working or whether they need to make changes.

Chemotherapy and diabetes

Research in a 2020 study suggests that in people with cancer and diabetes, high blood sugar due to chemotherapy may cause chemotherapy to be less effective. It may also increase the risk of chemotherapy side effects, such as a low white blood cell count and nerve damage.

Therefore, managing high blood sugar during chemotherapy is particularly important for people with diabetes.

Most people with preexisting diabetes will need insulin to help manage their blood sugar with cancer treatments.

People with type 2 diabetes who are not using insulin may need to start taking insulin injections. People may also need to start injections if they are having difficulty managing diabetes with other forms of insulin.

If people have difficulty managing their blood sugar levels, they may benefit from checking their levels more often throughout the day.

When to contact a doctor

People should contact a doctor if they develop symptoms of diabetes, such as:

• excessive thirst or increased urination
• fatigue
• blurry vision
• unexplained weight loss

Both chemotherapy and diabetes may increase the risk of peripheral neuropathy, which is damage to the nerves outside the central nervous system.

People should contact a doctor if they experience weakness, numbness, or tingling, particularly in the hands or feet.

Chemotherapy can weaken the immune system, which increases a person’s risk of infection. Diabetes also increases the risk of infection. People should contact a doctor if they have any symptoms of infection, such as:

• fever
• chills and sweats
• increased heartbeat
• new pain or swelling

Frequently asked questions

Why is glucose high in cancer patients?

Certain cancer treatments, including chemotherapy, hormone therapy, and steroids, can increase blood sugar levels.

Other factors, such as nutritional imbalances, reduced physical activity, obesity, infections, and stress, can also contribute to high blood sugar in people with cancer.

How do doctors treat diabetes in cancer patients?

Doctors may encourage people with cancer to manage diabetes using diet, exercise, and medications to lower blood sugar.

Can chemotherapy cause diabetes?

Chemotherapy may increase the risk of developing type 2 diabetes, as certain chemotherapy drugs can raise blood sugar levels.

Steroids, which people may take alongside chemotherapy, are the most common cancer treatment to cause diabetes.

Does chemo cause elevated blood sugar?

Chemotherapy drugs, including 5-fluorouracil and asparaginase, can cause high blood sugar and insulin resistance.

Summary

Chemotherapy, particularly in combination with steroids, can increase blood sugar levels and cause insulin resistance.

Managing blood sugar levels during cancer treatment is important to prevent complications, particularly for people with diabetes. Management strategies may include dietary changes, physical activity, and medications to lower blood sugar.

People who are undergoing cancer treatment should talk with a doctor about managing their blood sugar, particularly if they are experiencing treatment side effects, such as nausea and fatigue, that make it difficult for them to eat and exercise regularly.