8 Sneaky Signs You’re Dehydrated, According to a Dietitian

Dehydration doesn’t just cause thirst. It may be impacting your physical and mental health.

Reviewed by Dietitian Maria Laura Haddad-Garcia

Given that 55–65% of the human body is water, per StatPearls, staying hydrated is key. Dehydration rates are higher amongst older adults, but anyone is at risk for chronic, mild dehydration that can impair physical and mental function. Summer is a crucial season to be mindful of hydration since your hydration needs increase with hot, humid weather. Learn eight signs of dehydration, plus a few tips to stay hydrated even if plain water bores you.

Related: 4 Signs You’re Drinking Too Much Water

8 Signs You’re Dehydrated

1. You’re Thirsty

This one may seem obvious, but by the time you feel thirsty, you are typically already dehydrated. Luckily, thirst is usually a sign of mild or moderate dehydration, so it’s important to drink water soon after you feel thirst coming on so dehydration doesn’t become severe.

According to a 2018 study in Sports Medicine, however, there are some cases where quenching thirst isn’t enough to ensure adequate hydration and planned hydration is recommended. These include long bouts of exercise (over 90 minutes) in the heat, intense exercise with high sweating and times when performance is a concern. Yet, drinking to thirst should do the trick if you exercise for less than an hour, do low-intensity exercise or in cooler conditions.

Related: hould You Drink a Glass of Water After You Work Out? Here’s What Experts Say

2. Your Urine Is Super Dark

If you aren’t already, it can be helpful to start checking your urine color since it can be a good indication of your hydration status. When hydrated, your urine is typically pale yellow. If your urine is dark yellow, you could be moderately dehydrated. It can be a sign of severe dehydration if it is much darker.

3. You Haven’t Gone to the Bathroom in a While

Just like urine color could indicate your hydration status, so is your urine frequency or volume, per MedlinePlus, a resource of the National Institutes of Health (NIH). Urinating every 3-4 hours is pretty typical. If it’s been more than that since you’ve urinated, it could be a sign you’re dehydrated. Cutting back fluids on a long road trip may be normal to avoid making extra bathroom stops, but regularly going much of the day without urinating can mean you’re dehydrated.

4. You Feel Tired

Feeling fatigued can be another way that dehydration manifests itself. Water helps keep your body working smoothly and your mind sharp, so when you don’t have enough of it, your body has to work harder to do daily tasks, resulting in fatigue. A 2019 study in the International Journal of Environmental Research and Public Health found that, amongst college-aged participants, dehydration negatively affected vigor, while rehydration improved fatigue. There could, of course, be other reasons for fatigue, like inadequate sleep or poor quality of sleep, but if you’re fatigued, it’s worth considering whether you’ve had enough to drink.

5. Your Mouth and Lips are Dry

Your mouth and lips rely on hydration to stay moist. If you’re dehydrated, your mouth won’t have enough fluids to produce saliva. So, if you notice your lips are chapped and your mouth is dry, it’s probably time to grab a glass of water.

6. You’re Struggling With Concentration

Struggling to stay focused on the task at hand? Sure, it may be that you’re bored, but it may also be that you’re dehydrated. A 2019 study in the European Journal of Nutrition found a moderate association between dehydration in older adults and slower attention and processing speed. Similarly, the other 2019 study mentioned above also found that dehydration negatively impacted participants’ attention and short-term memory.

7. You Have a Headache

Feeling irritable and having a headache? We’ve all been there. Not drinking enough water may be the culprit. Studies have found that headaches can be a result of dehydration. For example, a 2021 review in Current Pain And Headache Reports found that dehydration can either cause a headache or exacerbate an underlying medical condition that could trigger a headache.

Related: 7 Conditions That Might Increase Your Risk of Dehydration, According to Health Experts

8. You Feel Dizzy or Confused

Beyond shifts in mood, dehydration can lead to disorientation and dizziness. Forgetfulness can also accompany these symptoms. If you have been out in the sun or have gone a while without drinking water, it’s important to hydrate as soon as possible. If these symptoms become severe, seek medical attention immediately.

How Much Water Should You Drink?

Hydration needs vary significantly from person to person, and there isn’t a great, uniform measurement for calculating someone’s hydration needs. The adequate intake (AI) for total water (from plain water, food and other beverages) is based on observations of people’s typical fluid intake and health status, per the Institute of Medicine of the National Academies. The recommended AI is 3.7 liters per day for men aged 19–30 and 2.7 liters per day for women in the same age range. In their findings, water and fluids accounted for about 81% of people’s total water intake, with water in food providing the remaining 19%. However, these fluid amounts only account for a relatively small age range, and they don’t represent recommendations for everyone. Even people between the ages of 19–30 can be okay consuming different amounts of fluid since fluid needs are different for each person.

That said, your urine can be a great way to gauge your hydration status. Pay attention to how often you’re urinating and the color for an indication of how hydrated you are. While dark yellow could be a sign of dehydration, taking vitamin C or B-complex vitamins can also cause dark urine, per MedlinePlus.

Keep in mind that your hydration needs will be higher if you live in a hot, humid climate or if you are very physically active and sweating a lot.

Other Ways to Prevent Dehydration

Staying hydrated doesn’t have to be a doozy. One of the easiest ways to avoid dehydration is to have water ready whenever possible. Bring a water bottle with you wherever you go, so it’s easy to take a sip here and there and stay ahead of dehydration. If you don’t love plain water, there are other ways to boost your fluid intake. Here are some tips:

• Make it a part of your routine. If you have a cup of coffee every morning, make sure you have a glass of water with it.

• Add flavor! If plain water bores you, add fruit, cucumber or lemon. Our Lemon, Cucumber & Mint Infused Water is a great way to start.

• Eat enough fruits and veggies. You don’t just get water from fluids; you also get it from foods. Fruits and veggies generally have a high water content, which contributes to our overall hydration for the day.

• Add some bubbles. Carbonated beverages can help add variety,, and many enjoy incorporating them into their hydration routine. You can even mix plain seltzer water with a splash of juice for a fun, refreshing hydration boost. Just make sure you’re not drinking too much.

Frequently Asked Questions

How can you test yourself for dehydration?

One of the best ways to measure dehydration is your urine color and frequency. On average, you should pee every 3-4 hours, and your urine should be pale yellow. If it’s been longer than this or dark yellow, it may indicate dehydration.

How can I rehydrate quickly?

Drinking plain water does the trick for most mild or moderate cases of dehydration. However, if you’ve become dehydrated from fluid loss from sweating, vomiting or diarrhea, you may want an oral rehydration solution with electrolytes for adequate rehydration.

How long does it take to rehydrate yourself?

Most of the time, you can rehydrate with water within a few hours if you’re experiencing mild or moderate dehydration. According to the Centers for Disease Control and Prevention (CDC), you may need an oral rehydration solution with electrolytes to rehydrate yourself, which could take a couple of days or longer if you have severe dehydration.

How do you feel when you’re properly hydrated?

When adequately hydrated, you tend to feel more energized and alert without dryness in your mouth or lips. Your thirst signals will be absent because your body’s fluid needs are met.

Can dehydration feel like a UTI?

Generally, symptoms of dehydration include dry mouth, infrequent urination, dark urine, headaches, dry skin and fatigue. In contrast, symptoms of a UTI include pain or burning during urination, frequent urination and cramping in the groin or lower abdomen, per the CDC. Dehydration is actually a risk factor for UTIs, so staying hydrated can help prevent these uncomfortable infections.

The Bottom Line

Staying hydrated can keep you feeling energized and alert throughout the day. Keep an eye out for dark urine, infrequent urination, dry mouth and fatigue, as these can be telltale signs of dehydration. Plain water is a great way to hydrate, but you can make it more fun by adding fruit, making a mocktail with juice and sparking water or adding more hydrating foods to your meals.

Related: Does Dehydration Cause High Blood Pressure?