Over the course of life, a person’s water needs change, too. Typically, with age, people lose muscle and gain fat, Shah says. Because fat contains less water than muscle, people generally need to consume less water with age to maintain healthy tissues.

Yet some older adults still do not consume as much water as they need, Shah says, because the bodies of older people – particularly, research suggests those over age 60 – are not as good at detecting thirst. The level of dehydration “that would make you thirsty at the age of 40 might not make you as thirsty at the age of 80,” he explains.

If you do feel thirsty, you’re probably dehydrated and should drink water, says Dr Alysia Robichau, a family and sports medicine physician at Houston Methodist.

There can be more subtle signs of dehydration, too, such as feeling constantly cold or having dry skin, Robichau says. People who are acutely or chronically dehydrated may also have headaches or dry eyes, she adds.

Because people go without water while they sleep, “most people wake up and they’re already dehydrated,” Chiampas says. It’s generally a good idea, he says, to start the day with a glass.

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It’s perfectly fine to add flavourings to your water or to drink carbonated water, Robichau says – but she warned that coffee and other caffeinated beverages may not be as hydrating as decaffeinated drinks. Drinking a caffeinated beverage, especially if you don’t drink them regularly, can reduce the ability of the kidneys to absorb water, leading you to lose additional water through urine. Alcoholic beverages are dehydrating, too.

Keep in mind that you can also get water from food. Some fruits and vegetables, such as watermelon and celery, are mostly water, Shah says.

Most people are unlikely to drink too much water, but it is possible, especially among endurance athletes who drink lots of water quickly, Chiampas says. Doing so can disrupt the body’s balance of sodium and potassium and lead to potentially fatal water intoxication. Keep in mind, too, that there is probably no health benefit to guzzling tons of water.

“There are a lot of excessively large water bottles being carried around by people these days,” Shah says. “But the overwhelming majority of people do not need to drink an excess of water.”