Most of us worry about illness as we grow older. Cancer, diabetes and heart disease all become concerns in our senior years.

But one relatively common and potentially fatal condition — dehydration — often flies under the radar.

Dehydration occurs when your body loses more fluid than it is taking in. The lack of fluid can prevent the body from functioning normally. When this happens, you may experience symptoms such as lack of urination, fainting and confusion.

Rapid heartbeat and rapid breathing also may occur. In severe dehydration, the body can go into shock. For some people, dehydration is fatal.

Dehydration can occur at any age. But seniors are particularly susceptible.

Most people’s sense of thirst diminishes with aging, so older adults may not drink enough fluids. The danger increases for seniors who have medical conditions — such as diabetes, cystic fibrosis or kidney problems — that cause them to urinate more often or sweat more profusely.

Older adults also have less fluid in their bodies than younger people.

Fortunately, the solution to dehydration is a simple one: Drink more fluids. This is especially important when you exercise or spend time outdoors in hot weather.

The National Institutes of Health (NIH) recommends taking the following steps to prevent dehydration:

• Drink more water every day. Fluid needs differ from person to person, so ask your physician how much water you should drink daily.
• Drink extra fluids after exercising or spending time outside on a hot day. The NIH says sports drinks can help restore minerals you may lose through sweating. Drinking additional fluids also makes sense when you are sick.
• Skip drinks with sugar and caffeine. Sugary drinks are especially bad for people with diabetes, and caffeinated drinks have a slight diuretic effect, meaning they lead to more frequent urination.

Many foods — including celery, cucumbers, watermelon and strawberries — also have a hydrating effect when you eat them.

It’s important to stay hydrated on a regular basis and not to wait until you are thirsty. By the time a senior is becoming thirsty, he or she already is becoming dehydrated, according to the Cleveland Clinic.

Dehydration is a common source of hospitalization among seniors. The Mayo Clinic suggests seeing a doctor if you or a loved one experience the following:

• Diarrhea for 24 hours or more
• Irritability or disorientation
• Sleepiness and a lower level of activity than normal
• An inability to keep down fluids
• Bloody or black stool

Allowing yourself to become dehydrated is just one medical faux pas people tend to make later in life.