During summer’s heat, it’s easy to become dehydrated without realizing it. And dehydration, which occurs when you lose more water via sweat and urine than you’ve taken in, can be especially dangerous for older adults.

A lack of sufficient fluid in the body can temporarily cause confusion and put you at risk for falls. When severe, dehydration can lead to a rapid or irregular heart rate, low blood pressure, fainting, and even death.

“How much water you have affects every body system,” says Jodi Stookey, Ph.D., an epidemiologist in San Francisco.

Staying well-hydrated becomes more difficult with age because your sense of thirst tends to diminish with time. Diuretics, often prescribed for high blood pressure and heart failure, can exaggerate water loss.

But you can protect yourself. Here’s how to stay hydrated during the warm months and year-round:

4 Steps for Staying Hydrated

Despite the widespread myth that everyone should consume eight 8-ounce glasses of water each day, there’s really no overarching rule about how much you need to drink to stay hydrated. What’s appropriate can vary a good bit from person to person.

Generally speaking, the heavier, taller, and more active you are (and the hotter and more humid the weather is), the more fluids you need to take in to cover your losses. To make sure you get enough:

Drink before you feel parched. To make up for that reduced sense of thirst, sip preemptively. By the time you actually feel thirsty, you might be mildly dehydrated.

Sip small amounts throughout the day. If you find it difficult to consume a full glass of water all at once, drink a bit at a time but do this frequently. Carrying a water bottle with you at all times can help remind you to drink.

Know that other beverages and foods count, too. In fact, all beverages (other than alcoholic drinks) will hydrate you.

That includes caffeinated drinks, even though coffee and tea are mild diuretics and can cause you to urinate more often. But these drinks will add more to your liquid stores than you’ll lose from extra urination, says Janet Mentes, Ph.D., a professor at the UCLA School of Nursing.

Soup, fruits, and vegetables are also good sources of liquid.

Consider your health. Ask your doctor whether medical conditions you have or medications you take affect your hydration needs.

And keep in mind that some health conditions, such as kidney disease and congestive heart failure, may make it dangerous to take in too much fluid. In these cases, your doctor can show you how to stay hydrated safely.

Know the Signs of Dehydration

Dehydration can be challenging to detect as we age because classic signs, such as dry mouth, thirst, fatigue, and skin that fails to spring back quickly when pinched, can also be caused by other factors.

In fact, a 2015 review of research by the independent Cochrane Collaboration found that there was no single reliable test for dehydration.

The color of your urine can sometimes be a clue. In general, healthy urine is the shade of pale straw. The darker your urine, the less hydrated you may be.

But aspirin, multivitamins, and certain fruits and vegetables can also affect the shade of your urine.

If you suspect you might be dehydrated based on your urine’s color and/or the other signs mentioned, try drinking two to three full glasses of water during the course of an hour or two, advises Marvin M. Lipman, M.D., Consumer Reports’ chief medical adviser.

If you still have symptoms of dehydration or don’t urinate within four hours, it’s wise to contact your doctor.

3 Surprising Causes

Taking in too little liquid is an important factor in dehydration, but the following play a role as well:

  • Infections that cause diarrhea, vomiting, excessive sweating, and fever. Tara Cortes, Ph.D., executive director of the Hartford Institute for Geriatric Nursing at New York University, suggests calling a doctor if you vomit repeatedly or have a fever of more than 101° F for more than a day or diarrhea for more than two days.
  • Medication that causes the kidneys to produce more urine, such as diuretics. Some over-the-counter drugs, such as laxatives, may also cause water loss.
  • Health conditions, such as poorly controlled diabetes, that lead to excessive water loss. A 2016 study in the Annals of Family Medicine found that obese people were more likely to be inadequately hydrated as well. Having dementia, Parkinson’s disease, or a stroke can also increase the chance of dehydration.
Editor's Note: This article also appeared in the June 2017 issue of Consumer Reports on Health.