Chemotherapy can make blood sugar management more difficult. This article explains how to better manage diabetes when you’re going through chemotherapy.

Managing blood sugar levels during cancer treatment, like chemotherapy, can be a difficult juggling act. But, maintaining tight control is crucial for both your overall well-being as a person living with diabetes as well as your cancer recovery journey.

Having both diabetes and cancer at the same time is more common than many people think; between 8% and 18% of all people with cancer also have diabetes.

This article will explain the connection between chemotherapy and blood sugar levels and how to better manage your diabetes throughout your chemotherapy treatments.

Chemotherapy can affect blood sugar levels in a multitude of ways.

Some chemotherapy drugs, such as asparaginase (Elspar), 5-fluorouracil (5-FU)–based chemotherapy, platinum-based chemotherapy such as cisplatin (Platinol), and busulfan (Busulfex, Myleran), can cause blood sugars to rise.

Steroids may also be prescribed during chemotherapy to help mitigate the side effects of treatment. Steroids often also cause hyperglycemia. Commonly prescribed steroids include glucocorticoids and corticosteroids such as dexamethasone, hydrocortisone, prednisone, and methylprednisolone (all of these steroids have multiple brand names).

Acute hyperglycemia is experienced in between 10% and 30% of all people going through chemotherapy. Longer-term high blood sugar levels are also common, especially in people with hematologic malignancies treated with L-asparaginase–based regimens and total body irradiation.

On the other hand, many people may struggle with the nausea brought on by chemotherapy treatment, and so have little to no appetite for regular meals and snacks.

Missed meals due to nausea can bring about low blood sugar levels, especially if the person is insulin-dependent and their medications aren’t lowered to meet their food intake.

Treatment for hyperglycemia during chemotherapy will depend on the severity of your high blood sugar levels and whether you have existing diabetes or not. Management will also be conducted with consideration to blood sugar variability.

Treatment will vary from person to person. But, in most cases, exogenous insulin is the best way to lower blood sugar levels during chemotherapy.

For people treated with once-daily corticosteroids, like prednisolone, intermediate-acting insulin is recommended due to the delay in blood sugar spike (usually within eight hours of the dose).

But, longer-acting glucocorticoids, like dexamethasone, may require long-acting insulin as the best choice to moderate blood sugar levels all day long. The same recommendation would apply to continuous or multi-dose steroids.

For chemotherapy drugs that cause sudden spikes in blood sugar levels, the best treatment is fast-acting insulin. For mild hyperglycemia (spikes <200 milligrams per deciliters), oral diabetes medications may be administered.

Additionally, for ongoing insulin resistance, staying hydrated and doing mild physical activity, such as walking or jogging, can help mitigate persistent high blood sugar levels throughout treatment.

You may experience low blood sugars (hypoglycemia) during chemotherapy, especially if you’re insulin dependent.

Chemotherapy can bring a lot of changes to your life and routine: it usually causes nausea, vomiting, and changes to appetite, it may make you lose weight, and it will affect your energy levels and sleep. Chemotherapy may also change the way foods taste.

You may want to skip meals and may not be hungry at all, which can cause low blood sugar levels.

The best thing you can do is find a fast-acting glucose source — such as juice, glucose tablets, or gel — that you can eat and keep down, even when you’re nauseous.

If you’re experiencing low blood sugar levels while you’re in the hospital or during a chemotherapy session, you may be able to get intravenous (IV) dextrose to raise your blood sugar without having to eat.

Talk with a doctor, especially if you take insulin, about adjusting your basal and bolus insulin settings while you go through chemotherapy treatment — especially if you’re experiencing many low blood sugar levels.

There’s no specific diet that you must follow if you have diabetes and cancer. But, it is always best to focus on eating whole, unprocessed foods, so you’re able to get the most nutrients possible.

If you don’t have much of an appetite, focus on eating whole foods that are also calorically dense, such as peanut butter, nuts, seeds, fruits, coconut, and avocado, to get as many calories in as possible when you eat. You may also want to consider foods that have a low glycemic index (GI), which correspond with nutrient dense foods.

Finally, you may seek out an oncology dietitian, who is a medical professional who is specifically trained to help people with cancer formulate the healthiest and most balanced meal plans for them and their health goals.

They can work with you to tailor a meal plan specific to your diabetes and cancer diagnoses while also keeping in mind the challenges that chemotherapy presents for eating.

Managing both diabetes and cancer isn’t an easy feat, and it can be even more difficult while going through chemotherapy.

Many chemotherapy drugs (and the steroids that are often prescribed along with them) cause insulin resistance and high blood sugar levels. Staying hydrated, seeking mild physical activity, and taking insulin (or an oral diabetes medication) are the best options to treat high blood sugar levels.

The effects of chemotherapy, including vomiting, nausea, and loss of appetite, may also cause low blood sugar levels. Finding a palatable source of glucose or even seeking an IV dextrose drip can help you manage low blood sugar levels while going through chemotherapy treatment.

Working with an oncology dietitian can help you create a meal plan that will help you meet both your diabetes and cancer health goals.