Can Drinking Water (or Not Drinking Enough) Affect Your Sleep?

Yes, hydration (and dehydration) can affect sleep.

“Being adequately hydrated is essential for ensuring your body functions as it should — and not just during the day,” explains Jackie Newgent, RDN, CDN, a New York City–based dietitian and the author of The Plant-Based Diabetes Cookbook. Being dehydrated can interfere with sleep, she says.

However, drinking too much water before bed can also interfere with sleep, says Vincent Pedre, MD, the medical director of Pedre Integrative Health in New York City and author of Happy Gut.

You’re not going to be sleeping soundly during the night if your bladder is waking you up to go, after all.

What Science Says About Hydration and Sleep

There’s plenty of evidence to show that drinking water and staying hydrated are essential to overall health. H2O accounts for up to 60 percent of the human body, and it helps with a wide variety of bodily functions — from cell growth to waste removal to digestion.^[1]

And while there’s less evidence investigating exactly how the quantity of water you drink (and when) affects sleep specifically, the data thus far suggests that when you’re less hydrated, you’re more likely to sleep less overall.

Both Newgent and Dr. Pedre point to one large cross-sectional study that showed that in a group of more than 20,000 American and Chinese adults, those who self-reported sleeping less than six hours nightly, on average, were more likely to also have lower hydration status (as measured by analyzing participants’ urine samples) than those who reported sleeping eight hours or longer each night.^[2]

(The researchers were investigating the connection because getting too little sleep and getting too much sleep have both been previously linked to kidney problems.)

On the other hand, a different, small study found that dehydration did not affect the amount or quality of sleep in 12 healthy young adults, according to sleep tests conducted in a lab setting, before which participants were given specific instructions on how much noncaffeinated liquid to drink before each test.^[3]

Another way sleep is connected to hydration has to do with the hormone vasopressin. It’s produced by the body and released during deep sleep to increase water absorption in the kidneys.^[4]

It’s released more readily the longer you’ve been asleep, to help keep the body hydrated so you don’t need to wake up to drink water, Pedre explains. “Disruptions in the late sleep period may lead to dehydration by disrupting the release of vasopressin.”

This means that cutting your sleep short may actually contribute to dehydration too.

Can Dehydration Disrupt Sleep?

While research hasn’t yet answered all of the questions around why hydration affects sleep, experts do know a lot about what can go wrong with sleep when you’re dehydrated (as well as if you drink too much water). “Even minor symptoms of dehydration can negatively impact sleep, due to discomfort,” Newgent says.

Pedre adds that dehydration can cause the following symptoms, which can consequently disrupt sleep:

• Muscle Cramps and Spasms Dehydration may contribute to muscle spasms and cramps, which is when there is a painful tightening of the calf or foot muscles. The pain and discomfort can make it difficult to fall asleep or may potentially wake a person up in the middle of the night, as muscle mass is composed of about 76 percent water.^[5]

• Headaches Dehydration can trigger headaches and migraine attacks in some people, which can complicate falling asleep and staying asleep.
• Early Morning Thirst Being thirsty can cause someone to wake up in the middle of the night or early morning.
• Dry Mouth Dry mouth can also cause discomfort that may aggravate sleeping.

Can Drinking Too Much Water Disrupt Sleep?

Yes, it’s certainly possible to drink too much water before you go to sleep, Newgent says, “since you may need to take a trip or two to the bathroom to urinate in the middle of the night.”

When the need to get up to pee in the middle of the night disrupts sleep or keeps you from falling back asleep afterward, doctors refer to this as nocturia.

Some research suggests that sleep position may make you more likely to have to wake up during the night to urinate. The studies have suggested that the kidneys filter more blood while the subject is lying in the prone position (on one’s stomach), which fills the bladder faster and increases urine output, as opposed to being in the supine position (on one’s back, facing up). Note that one study was done in dogs.^[6]

And another study pointing to this conclusion was small, involving 14 adult men.^[7]

Pedre says the pair of studies suggest that excess water intake close to bedtime may be more likely to cause you to have to urinate sooner than if you had drank the same amount of water at a time of day when you were not lying down (though he adds that the evidence should be considered preliminary). What we do know, he says: “Excess water intake near bedtime is often going to wake you up with a full bladder in the middle of the night.”

So, How Much Water Should You Drink Before Bedtime? 3 Tips

“If you’re working on improving your sleep, you want to hydrate during the day, and try to reduce fluid intake later in the day, especially right before bedtime,” says Pedre.

Here are some tips:

1. Pay Attention to When You Hydrate During the Day

Try avoiding fluids at least one hour prior to bedtime helps you avoid extra nighttime awakenings to pee, Pedre adds. “However, if you tend to have a hyperactive bladder or incontinence, it’s best to avoid water starting two to three hours prior to bedtime.” (But make sure you’re hydrated prior to that.)

When you do drink water late at night, Newgent suggests keeping it to small sips as needed.

2. Pay Attention to Other Things That Hydrate and Dehydrate You During the Day

It’s also important to pay attention to other factors that affect hydration throughout the day. Coffee consumption and the amount you sweat can both be dehydrating and potentially deplete your body of essential minerals.

Caffeine can act as a mild diuretic (meaning it makes you have to pee more and dehydrates you). Plus, it’s a stimulant. Though caffeine sensitivity varies by individual, most recommendations suggest cutting off caffeine consumption at least eight hours prior to bedtime.^[8]

Excess alcohol intake can also have a slight diuretic effect and disrupt sleep cycles. “Try to keep alcoholic beverages to no more than one drink in the evening,” Newgent recommends — and likely less is better. This is especially important the older you are, since there is a higher risk of dehydration with alcohol use as people age.^[9]

Consuming water-dense foods can contribute to hydration and your daily water intake. Some of the most hydrating foods you can eat include cucumbers, lettuce, celery, squashes, strawberries, and watermelon, all of which are composed of more than 90 percent water.^[10]

3. Pay Attention to Other Things That Affect Nighttime Hydration

Keep in mind, there are a few other factors that can affect hydration and its relationship to sleep, including:

• Nighttime Sweating Newgent says that if you tend to sweat at night, you can have a notable amount of “insensible water loss” or lost body fluid that cannot be easily measured and can also contribute to dehydration.^[11]

If you tend to sweat easily at night, Newgent suggests taking steps to make for a cooler sleep environment, such as setting your thermostat to a temperature that’s bedtime-comfortable for you — which is likely cooler than a daytime temp. The ideal bedroom temperature for most people is around 65 degrees F, though it may vary from between 60 to 67 degrees F.^[12]

For some people, and depending on the local climate, the ideal temperature may be a little higher; you’re aiming for a temperature at which the ambient room feels cool.

• Mouth Breathing Mouth breathers can also experience insensible water loss at night. One study found that heavy mouth breathers expel 42 percent more water than those who breathe through their nose.^[13]

The Takeaway

Being adequately hydrated is essential for allowing your body to function as it should during your waking hours and during sleep. Research shows that dehydration can disrupt sleep. And drinking too much water before sleep can increase the frequency of nighttime awakenings (first and foremost because you are more likely to need to wake up to pee).

Additional reporting by Kristeen Cherney.

Sources

1. The Water in You: Water and the Human Body. U.S. Geological Survey. May 22, 2019.
2. Rosinger AY et al. Short Sleep Duration Is Associated with Inadequate Hydration: Cross-Cultural Evidence from U.S. and Chinese Adults. Sleep. February 2019.
3. Aristotelous P et al. Effects of Controlled Dehydration on Sleep Quality and Quantity: A Polysomnographic Study in Healthy Young Adults. Journal of Sleep Research. February 2018.
4. Cuzzo B et al. Physiology, Vasopressin. StatPearls. August 14, 2023.
5. Serra-Prat M et al. Total Body Water and Intracellular Water Relationships With Muscle Strength, Frailty, and Functional Performance in an Elderly Population: A Cross-Sectional Study. The Journal of Nutrition, Health, and Aging. January 2019.
6. Reinhart GA et al. Role of the Renin-Angiotensin System in Mediating the Effects of Posture on Renal Function. American Journal of Physiology. July 1996.
7. Pump B et al. Effects of Supine, Prone, and Lateral Positions on Cardiovascular and Renal Variables in Humans. American Journal of Physiology. July 2002.
8. Pacheco D et al. Caffeine and Sleep Problems. Sleep Foundation. April 17, 2024.
9. How to Stay Hydrated: A Guide for Older Adults. National Council on Aging. March 18, 2024.
10. 15 Foods That Can Help You Stay Hydrated. UCLA Health. June 17, 2022.
11. McNeil-Masuka J et al. Insensible Fluid Loss. StatPearls. July 25, 2023.
12. Pacheco D et al. The Best Temperature for Sleep. Sleep Foundation. March 7, 2024.
13. Svensson S et al. Increased Net Water Loss By Oral Compared to Nasal Expiration in Healthy Subjects. Rhinology. March 2006.

Important Notice: This article was originally published at www.everydayhealth.com by Leah Groth where all credits are due. Medically reviewed by Justin Laube, MD

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