Do you drink water from the night before? Better do not do it

Leaving a glass of water on the bedside table is a fairly common practice. If we wake up thirsty in the middle of the night or in the morning, we’ll be thankful that water is readily available. But is it safe to drink water from the glass on the nightstand?

There are no expiration dates on bottled water, so it doesn’t have to go bad. But whether or not we should drink stale water that has been sitting on the nightstand or counter all night, or for hours in a hot car, is up for debate.

To find out what can happen if we leave a glass of water out overnight and drink it, we’ll look at the possible dangers.


Drinking water from the glass on the nightstand doesn’t have to be a health hazard. However, we may not have taken into account the many factors that affect the quality of drinking water.

Contaminated water

Without a lid, contaminants can get into the glass of water. An open glass is susceptible to contamination by dust, germs, and insects. This also includes anything else that floats or flies in the air.

The body digests insects or arthropods like any other food, so this may not be as detrimental to health as it is disgusting. However, science shows that toxic chemicals can be found in house dust, and over time, drinking large amounts is associated with health problems.

bitter taste

If we’ve ever had a glass of water that we left out overnight, we may have noticed the subtle difference in taste. When you leave a glass of water out overnight, gases in the air, including carbon dioxide, dissolve in the water. When carbon dioxide dissolves in water, it turns into carbonic acid. In turn, the acid forms carbonates and bicarbonates, which lower the pH and give it an acidic or bitter taste.

Although water does not contain fats, proteins or sugars, chemical reactions take place when it is in a glass. And the more time passes, the worse its taste will be. There are still no studies that show one hundred percent why water becomes rancid, but there are theories that relate it to the number of hours it is exposed in a glass. Diego Sevillano Borkowski, a specialist, defends that although there are no microbes in a glass, it does not imply that chemical reactions do not occur.


The mouth is home to about 700 species of microbes, according to experts. And that’s a lot of bacteria. Drinking from a glass will result in backwashing, when liquids mix with bacteria in the mouth before returning to the container. That’s why experts say we should avoid drinking from a glass of water that’s been left out overnight if someone else used it before.

Our mouths contain numerous species of bacteria that can contaminate the water bottles or glasses we drink from. Although our own bacteria are unlikely to cause harmful effects if we reuse a water bottle or glass after leaving it out overnight, these germs could be harmful to other people and vice versa.

beber agua mesita de noche

So we can’t drink water from the glass?

Not at all, the water does not cease to be drinkable at any time. The problem is that not being in a sealed container (bottle), the water is exposed to bacteria from the environment.

Tap water has a certain percentage of chlorine to prevent microbes from colonizing it. Once it leaves the pipe, the chlorine evaporates and is exposed to any microorganism that wants to multiply. Dust or insects can “infect” the glass of water that we innocently leave on the table for when we are thirsty. The more hours we leave it exposed, the greater risk there will be.

In addition, we also have to take into account the temperature. Although the water does not contain sugars or macronutrients, the temperature also influences the taste of the water. There is no need to be afraid, if we filter the water and boil it, we will be able to consume it again as new. Although the fastest option is to opt for closed water bottles.

From now on, will you want to drink water from the glass on your bedside table or are you already looking at it with different eyes?