Should you drink a glass of water first thing in the morning?

December 28, 2025 •

4 min read

The human body is composed of approximately 60% water, and after hours of sleep without any fluid intake, it can become mildly dehydrated. So, should you drink a glass of water first thing in the morning? Experts say a simple glass of water upon waking can offer notable benefits, though some common claims are more myth than fact.

Quick Summary

This article explores the evidence behind consuming water immediately after waking. It covers potential benefits like rehydration, metabolism stimulation, and improved mental clarity, while also debunking common myths and providing practical tips for morning hydration routines.

Key Points

Rehydrate After Sleep: A glass of water in the morning effectively replenishes fluids lost overnight through respiration and perspiration.
Boost Mental Clarity: Combat morning brain fog and improve concentration by reversing the mild dehydration that occurs during sleep.
Kickstart Metabolism: Drinking water can temporarily increase your metabolic rate, providing a small energy and calorie-burning boost.
Aid Digestion: It helps wake up your digestive system, promotes regularity, and can alleviate heartburn by diluting stomach acid.
Myth Busting: Scientific evidence does not support the claims that morning water 'flushes toxins' or is exclusively responsible for weight loss.
Stay Hydrated Overall: The timing of water intake is less important than maintaining consistent hydration throughout the entire day.

The Case for Morning Hydration

After eight hours of sleep, your body has gone through a lengthy period without fluid intake, which naturally leads to a state of mild dehydration. While your body has an effective thirst mechanism to prompt you to drink throughout the day, starting with a glass of water can be a gentle way to replenish fluids and get your body and mind moving. According to Dr. Casey Kelley, an internist, drinking water upon waking helps restore lost liquid, particularly if you sleep in a warm room or with your mouth open.

Benefits of Starting Your Day Hydrated

Many benefits associated with morning water intake are well-supported by science, stemming from reversing the effects of mild dehydration.

Replenishes Lost Fluids: Overnight, the body loses water through breathing and perspiration. A morning glass of water helps to replenish this deficit, ensuring proper bodily function from the start.
Boosts Mental Performance: Mild dehydration (1-2% of body weight) can impair cognitive function, including memory, concentration, and alertness. A study found that rehydrating with even a single glass of water in the morning could reduce feelings of anger, fatigue, and poor mood.
Stimulates Metabolism: Studies have shown that drinking water can temporarily increase your metabolic rate. For example, some research indicates that drinking about two cups of water can increase a person's metabolic rate by 24–30% for approximately an hour. While not a magic weight-loss solution, this kickstart to your metabolism can be a helpful boost.
Aids Digestive Health: Water is crucial for healthy digestion. A glass in the morning helps wake up the digestive system, promotes regular bowel movements, and can prevent constipation by softening stool. It can also help alleviate heartburn by diluting stomach acid.
Supports Skin Health: Since the skin is composed of a significant percentage of water, proper hydration is important for its health and appearance. While drinking water won't prevent wrinkles caused by aging, it can improve skin elasticity and reduce dryness, contributing to a healthy glow.

Debunking Morning Water Myths

While many benefits of drinking water are real, certain claims specific to morning water lack strong scientific evidence. The key takeaway is that overall daily hydration is what truly matters, not just the time of day.

Myth: It 'Flushes' All Toxins: The body's natural detoxification system, primarily the kidneys and liver, doesn't need a specific “flush” from morning water. While water is essential for these organs to function, they filter waste regardless of the time of day you drink.
Myth: Only Morning Water Contributes to Weight Loss: Water can aid weight loss by increasing feelings of fullness and boosting metabolism (thermogenesis). However, these effects are not exclusive to morning water consumption. Drinking water before any meal or increasing overall intake throughout the day has similar effects.
Myth: Dark Morning Urine is a Sure Sign of Dehydration: Dark urine in the morning is simply more concentrated because you haven't consumed fluids overnight. It's a normal occurrence and not a reliable indicator of your overall hydration status. Hydration levels must be measured throughout the day.

Comparison: Morning Water Benefits vs. Myths


Feature	Supported by Science	Considered a Myth	Notes
Rehydration	Yes	No	Replenishes fluids lost overnight through natural processes.
Metabolism Boost	Yes (temporary)	No	Can increase metabolic rate for a short period, regardless of timing.
Mental Clarity	Yes	No	Corrects mild dehydration that can negatively affect mood and focus.
Digestive Aid	Yes	No	Helps wake up the digestive system and soften stool to prevent constipation.
Toxin Flush	No	Yes	The body's organs (kidneys, liver) detoxify continuously and efficiently.
Skin Detox	No	Yes	While hydration helps skin, targeted "detoxification" through water isn't scientifically proven.
Weight Loss (exclusive)	No	Yes	Water helps with weight management, but the effect isn't limited to morning consumption.

Practical Steps for a Morning Hydration Routine

Implementing a morning water habit can be simple and beneficial. Here are some steps to make it a part of your daily routine.

How to Start and Optimize Your Morning Water

Start Small: If you're not used to drinking water right away, start with a smaller glass (8 oz) and gradually increase the amount over time. Some experts suggest aiming for around 500-600 milliliters (approx. 2 cups).
Temperature: The temperature of the water can affect how you feel. Some people find warm water more soothing and better for digestion, while cold water can provide a refreshing jolt and a small metabolic boost. Choose what feels best for you.
Add Flavor: For those who find plain water unappealing, adding a slice of lemon, lime, or cucumber can make it more palatable and provide an extra boost of vitamins and antioxidants.
Set a Reminder: Place a glass of water on your nightstand the night before so it’s the first thing you see in the morning. This removes the barrier of having to go and get it.
Wait Before Eating: Some advise waiting 30-45 minutes after drinking water before consuming breakfast to allow your body to absorb the fluid and kickstart your digestive system.

Conclusion: The Bottom Line on Morning Water

Ultimately, the act of drinking water first thing in the morning is a healthy and simple habit. While it won't cure diseases or perform detox miracles as some myths suggest, it offers tangible benefits that set a positive tone for the day. It effectively rehydrates the body after a long sleep, improves mental clarity and energy, and aids digestion. The most important factor, however, is not the time you drink but ensuring adequate hydration throughout the entire day. For most people, a morning glass of water is a small step with a noticeable and positive impact on their daily well-being. By focusing on overall hydration and not getting caught up in unproven claims, you can easily build a habit that serves your body well. For a deeper dive into overall hydration best practices, see resources like WebMD's guide on the topic.

Frequently Asked Questions

There is no universally prescribed amount, but many experts suggest starting with a glass of 250-500ml (approx. 1-2 cups). You can gradually increase this amount as your body adjusts.

Both have benefits. Warm water may aid digestion and be soothing, while cold water can provide a refreshing wake-up and a slight metabolic boost. The best choice depends on personal preference and how your body responds.

No. The body's kidneys and liver handle detoxification continuously and efficiently. Water supports these functions but doesn't perform a special 'flush' in the morning.

It can be a supportive habit. Water can help you feel full, which may lead to a reduced calorie intake at breakfast. However, this effect is not unique to morning water and is part of overall healthy hydration habits.

Staying hydrated generally benefits skin health by improving elasticity and reducing dryness. While morning water is a step towards this, it won't prevent wrinkles and is most effective when hydration is maintained throughout the day.

It's best to have water first to rehydrate your body. While coffee is not as dehydrating as commonly thought, it's still smart to replenish lost fluids before introducing caffeine, which can have a mild diuretic effect.

For most healthy individuals, no. Drinking excessive amounts too quickly, however, can lead to frequent urination or, in extremely rare cases, hyponatremia (water intoxication), but this is not a concern for a single glass.

Adding lemon can enhance flavor and provide extra Vitamin C. Some experts also suggest it can help prevent kidney stones. It is a simple way to make morning hydration more appealing.