Average normal body temperatures in older adults are slightly lower than in younger adults. So when an older adult is sick, their fever temperatures may also be lower.

These temperatures in older adults may be signs of an infection, such as COVID-19 or the flu:

• A single temperature reading higher than 100°F 
• Multiple temperature readings above 99°F 
• A rise in temperature greater than 2°F above the person’s normal body temperature

The National Institute on Aging explains that the flu is more dangerous for older adults for a few reasons. One reason is that the immune system — which helps your body fight infections — weakens as you age. For example, because your body is busy fighting off the flu, you might pick up a secondary infection such as pneumonia. A second reason is that older adults are also more likely to have other health conditions, like diabetes, that increase their risk for complications from the flu.

The good news is the flu vaccine reduces your risk of getting the flu and of getting seriously ill if you do get sick with the flu. Flu vaccination is especially helpful for people with chronic health conditions. For example, it has been linked to lower rates of heart problems (cardiac events) among people with heart disease and fewer hospitalizations among people who have chronic lung disease or diabetes.

Learn more about older adults and flu.