7 Consequences of Not Drinking Enough Water Throughout the Day

I can’t help but wonder what our nomadic ancestors would think about us clutching water bottles 24/7. We do this despite the fact that our lives aren’t exactly physically grueling. It’s kinda funny if you think about it. Still, while we may have taken water dependence to the extreme, our instincts aren’t wrong; drinking enough water is important, as water is required to perform nearly every bodily function.

According to Maya Feller, RD, many people are unknowingly mildly dehydrated most of the time. “Sometimes when people hear ‘mildly dehydrated,’ they wonder how that could be,” she says. “But you lose water regularly—when you breathe, when you sweat, when you are digesting food—without being aware.”

And when our bodies are low on water, there are consequences; some are obvious and just mildly annoying, but others can be crippling.  Below, how insufficient water consumption negatively impacts your daily life.

This is what happens if you’re not drinking enough water

1. Headache

Our noggins are often the first—or at least, the most obvious—part of our bodies to signal H₂O deficiency, and they do so in the form of mild to severe pain. “The blood vessels around our brains are very sensitive, so if you do not drink sufficient water, they may react to the change in blood volume, and that may increase the likelihood of headache,” explains dietitian Dana Hunnes, RD, PhD, an adjunct professor at the UCLA Fielding School of Public Health.

2. Constipation

When there’s not enough water running through the digestive system, it can show signs of struggle, which typically manifest as constipation. “Not having enough water in the gastrointestinal tract can make stool drier and therefore more difficult to pass,” explains Hunnes. And the more fiber you take in, the more water you need to be drinking, as fiber requires water in order to be properly digested. Without it, you may experience bloating and gas on top of the constipation. (Feller also notes that water is required for the formation of saliva, which is also necessary for overall gut function. Digestion, after all, begins in the mouth.)

3. Fatigue

In 2020, you could be fatigued for any number of reasons, so it might be hard to connect this symptom to dehydration. Still, Hunnes says that not having enough water in the body can make you feel tired. She says this has to do, at least in part, with the changes in blood volume that result from water shortages. So if you’re feeling the slump, having a glass of water might be a better first step than sipping a caffeinated drink, which could further dehydrate you.

4. Hunger

Dehydration can also make you feel hungry before you even register that you’re thirsty, say Feller and Hunnes. This is because both signals come from the same part of the brain—the hypothalamus—and wires can get crossed, so to speak. The result might be unnecessary snacking, so it’s worth drinking water before eating if you know you’ve recently eaten and shouldn’t be hungry again.

Plenty of foods are hydrating if you’re worried about drinking enough water:

5. Impaired brain function

Neuroscientist Lisa Mosconi, PhD, the author of Brain Food: The Surprising Science of Eating for Cognitive Power, says staying hydrated is her number one priority when it comes to brain health. In fact, even a 2 to 4 percent decrease in your body mass due to dehydration can throw the brain off balance. One example of the problems that can result? One study found that mild dehydration produced a significant increase in minor driving errors during a long drive.

6. Bad mood

Not being properly hydrated can affect your mood, too, according to a small study of young women that showed how mild dehydration has negative effects. Feller notes that the body requires water to produce hormones and other neurotransmitters, so it makes sense that dehydration causes mood disturbances.

7. Overheating

Hydration helps to maintain a comfortable body temperature, notes Feller, which is why dehydration can make you feel overheated, especially in hot environments. If you’re feeling the heat, you might want to try raising a glass before you lower the thermostat, because the problem may simply be that you need more coolant, so to speak.