Can the flu make diabetes worse?

Diabetes is one of the most common health conditions in the world, affecting hundreds of millions of people. In the United States, diabetes is estimated to affect more than 11 percent of the population.

The most common form of diabetes is type 2 diabetes, which accounts for 90 to 95 percent of all diabetes. T2D is caused by several contributing factors, including overweight/obesity, sedentary lifestyle, and genetics. There is also type 1 diabetes, which is an autoimmune disease, and gestational diabetes, a type of diabetes that occurs during pregnancy.

Influenza is one of the most common illnesses in the world. Influenza viruses cause respiratory infections (commonly referred to as “the flu”), with symptoms that can include fever, chills, muscle aches, headache, congestion, and cough. Millions (sometimes tens of millions) of people in the United States become infected with the flu every year, with most cases occurring during “flu season,” or the fall and winter months.

A flu shot protects against the flu

All adults are encouraged to get an annual flu vaccine, commonly referred to as a “flu shot.” An annual flu shot helps prevent a person from getting sick and spreading the virus to others. It also helps reduce the severity of flu symptoms if a person does catch the flu.

For people with chronic health conditions—including people who have any form of diabetes—annual flu shots are considered even more important.

People with diabetes have a significantly greater risk of experiencing severe illness and complications from the flu, including pneumonia, heart attack, stroke, and sepsis. Receiving an annual flu shot has been shown to reduce the risk of these outcomes.

People with diabetes are advised to get an injectable flu vaccine. The flu vaccine that is available as a nasal spray contains a live (though extremely weakened) virus, and it is not the preferred choice for people with diabetes and other chronic health conditions, or people who are pregnant.

How the flu can make diabetes worse

Another reason to get the flu shot—having the flu can make diabetes worse.

All forms of diabetes cause elevated levels of blood glucose. Blood glucose is a type of sugar that circulates in the blood. It is the main energy source for cells throughout the body. In order to use glucose for energy, cells require a hormone called insulin.

When a person has diabetes, the body cannot use insulin and/or does not produce enough insulin. This causes blood glucose levels to become chronically elevated. Over time, this can damage many systems throughout the body. Diabetes complications include cardiovascular disease, kidney disease, neuropathy (nerve damage), vision loss, and many other health problems, especially when poorly managed.

Keeping blood glucose levels well controlled is critical when managing diabetes. The flu can worsen diabetes because it makes blood glucose levels more difficult to control.

Part of the response that occurs in the body when a person is sick is a release of several hormones, including the hormone cortisol. Also known as the “stress hormone,” cortisol helps the immune system get to work fighting off the infection. It also raises blood glucose levels. While this is temporary, it does require careful monitoring. If a person is taking insulin to manage diabetes, insulin doses may need to be adjusted while sick.

Certain cold and flu medications can also increase blood glucose levels—another reason it is always a good idea to talk to a healthcare provider and/or pharmacist before taking any medication.

It may also be difficult to eat normally when experiencing flu symptoms like fever, chills, muscle aches, and general malaise. Not eating enough can contribute to episodes of low blood sugar (hypoglycemia).

Planning for sick days should be a part of a diabetes treatment plan—and is something that anyone with diabetes should discuss with a healthcare provider. The Centers for Disease Control and Prevention also recommend prompt treatment with flu antiviral therapy for people with diabetes who have flu illness or suspected flu infection.