Why Do I Drink More Water on Keto?

November 18, 2025 •

4 min read

According to research, for every gram of carbohydrates your body stores as glycogen, it also stores approximately three to four grams of water. This tight relationship between carbs and water storage is a key reason why you drink more water on keto, especially during the initial transition period.

Quick Summary

Starting a ketogenic diet triggers glycogen depletion and electrolyte shifts, causing your body to flush out excess fluids. This metabolic change necessitates increased water intake to prevent dehydration and manage symptoms like thirst and fatigue.

Key Points

Glycogen depletion causes initial water loss: Cutting carbs forces your body to burn through glycogen stores, which release significant amounts of stored water, increasing your need for fluids.
Reduced insulin increases sodium excretion: Lowered insulin levels on a keto diet signal the kidneys to flush out more sodium and other electrolytes, causing fluid loss and driving thirst.
Ketones have a diuretic effect: The production of ketones during fat metabolism increases urination, further contributing to dehydration and the need to drink more water.
Plain water alone is not enough: Drinking only plain water can dilute remaining electrolytes, potentially worsening keto flu symptoms like headaches, fatigue, and muscle cramps.
Electrolyte replenishment is crucial: To prevent dehydration and manage symptoms, you must replenish lost electrolytes like sodium, potassium, and magnesium through salt, bone broth, or supplements.
Poor hydration can lead to serious complications: Inadequate fluid and electrolyte intake can increase the risk of kidney stones, severe electrolyte imbalances, and impaired fat metabolism.

The Core Mechanisms Behind Increased Thirst on Keto

Transitioning to a ketogenic diet requires your body to undergo a significant metabolic shift, moving from using glucose (from carbohydrates) to burning fat for fuel. This process, known as ketosis, involves several physiological changes that directly impact your body's fluid balance. The most important factors contributing to your increased water intake are the depletion of glycogen stores, reduced insulin levels affecting sodium, and the diuretic effect of ketones themselves.

Glycogen Depletion: The Initial Water Flush

When you dramatically cut carbohydrate intake, your body first uses up its stored glucose, known as glycogen. Glycogen is a polysaccharide that is heavily hydrated, with a significant amount of water bound to it. As your body burns through these glycogen stores for energy, it releases the associated water, which is then flushed out of your system primarily through increased urination. This initial water loss can be substantial, often resulting in a noticeable drop on the scale within the first week. This sudden fluid loss leaves your body in a depleted state, triggering thirst to signal the need for rehydration.

Reduced Insulin and Sodium Excretion

One of the primary goals of the ketogenic diet is to lower insulin levels. While beneficial for managing blood sugar, this decrease in insulin also has a major impact on kidney function. Lower insulin signals the kidneys to excrete more sodium and other electrolytes, such as potassium. Sodium plays a critical role in fluid balance, as it helps your body retain water. When you lose more sodium, your body's ability to hold onto water is diminished, leading to further fluid loss. This creates a cycle where you are constantly losing fluids and electrolytes, which in turn drives the feeling of increased thirst.

Ketones as a Diuretic

As your body breaks down fat for energy, it produces compounds called ketones. While serving as an alternative fuel source, ketones also have a diuretic effect. This means they cause an increase in urine production as the body works to excrete excess ketones. This constant need to urinate contributes significantly to your overall fluid loss. If not properly addressed with increased water intake, this can easily lead to dehydration and exacerbate symptoms like fatigue and headaches, commonly known as the "keto flu".

Managing Hydration and Electrolytes on Keto

To counteract the dehydrating effects of ketosis, a proactive approach to hydration and electrolyte balance is essential. Simply drinking more plain water is not enough, as this can further dilute your remaining electrolytes and worsen symptoms.

Comparison Table: Plain Water vs. Electrolyte Intake on Keto


Feature	Plain Water	Electrolyte Intake (Salt, Broth, Supplements)
Primary Role	Replaces lost fluid volume.	Replenishes essential minerals lost due to diuretic effect.
Effect on Thirst	Provides temporary relief, but thirst often returns quickly.	Addresses the root cause of thirst by restoring mineral balance.
Risk of Imbalance	High risk of hyponatremia (low sodium) if consumed in large quantities without electrolytes.	Lowers the risk of electrolyte imbalances and related side effects.
Keto Flu Impact	Can worsen symptoms like headaches and fatigue by diluting electrolytes.	Directly combats and prevents keto flu symptoms.
Optimal Strategy	Combined approach: Plain water for volume, electrolytes for mineral balance.

Practical Strategies for Maintaining Hydration

Start the day strong: Begin your morning with a large glass of water fortified with a pinch of sea salt or a keto-friendly electrolyte supplement. This helps replenish fluids and minerals lost overnight.
Sip throughout the day: Instead of chugging large quantities of water at once, consistently sip fluids throughout the day. Listen to your body's thirst signals, but don't wait until you're already parched.
Include electrolyte-rich foods: Incorporate keto-friendly foods high in electrolytes like avocados (potassium), spinach and leafy greens (magnesium), and bone broth (sodium). Salt your food liberally to help retain fluid.
Consider supplements: For those with higher activity levels or more intense symptoms, a sugar-free electrolyte powder can be a convenient and effective way to ensure adequate intake of sodium, potassium, and magnesium.
Monitor urine color: A simple check can indicate your hydration status. Light yellow or clear urine is a sign of good hydration, while dark yellow urine suggests you need more fluids.

Conclusion

Increased thirst on the keto diet is a direct and understandable consequence of several physiological changes, including glycogen depletion, lowered insulin levels, and the diuretic effect of ketones. This increased need for hydration, combined with accelerated electrolyte loss, is a major contributing factor to the common side effects known as the "keto flu". By understanding these mechanisms, keto followers can move beyond simply drinking more water and adopt a smarter hydration strategy. Combining regular fluid intake with intentional electrolyte replenishment—through food, broth, or supplements—is the most effective way to prevent dehydration, alleviate symptoms, and support the body's successful transition into ketosis. Prioritizing this balanced approach will make your keto journey smoother and more sustainable, ensuring you stay energized and clear-headed.

Potential Complications from Poor Hydration

Poor hydration on a keto diet can lead to more than just thirst. Overlooking the body's need for fluids and electrolytes can result in more serious issues:

Kidney stones: Dehydration, combined with changes in mineral balance, can increase the risk of kidney stone formation.
Severe electrolyte imbalances: Imbalances can disrupt nerve function, causing muscle cramps and, in severe cases, dangerous heart arrhythmias.
Exacerbated keto flu: Insufficient hydration intensifies symptoms like headaches, brain fog, and fatigue, making the initial adaptation period much more difficult.
Impaired fat metabolism: Water is required for the beta-oxidation process that breaks down fats. Inadequate hydration can slow down this key metabolic function.

Understanding and addressing these risks is a critical component of a healthy ketogenic lifestyle. Focusing on proper hydration and electrolyte intake is a powerful way to mitigate these challenges and promote overall well-being. For comprehensive nutritional planning, resources like the Children's Hospital of Philadelphia offer valuable insights on fluid intake, especially for those with specific health considerations.

Frequently Asked Questions

You feel thirstier on keto primarily because of glycogen depletion and increased electrolyte excretion. When your body burns its stored carbohydrates (glycogen), it releases the water bound to them, which you then flush out. Lowered insulin levels also cause your kidneys to excrete more sodium, leading to further fluid loss and triggering thirst.

Yes, drinking too much plain water without replenishing electrolytes can be problematic. This can dilute your blood's sodium levels, a condition called hyponatremia, which can worsen keto flu symptoms like fatigue, headaches, and muscle cramps. The key is to balance your water intake with adequate electrolytes.

The keto flu is a collection of temporary, flu-like symptoms, including headaches, fatigue, and muscle cramps, that some people experience when first starting keto. These symptoms are primarily caused by dehydration and electrolyte imbalances resulting from the rapid fluid loss during the transition into ketosis.

A reliable way to monitor your hydration is by observing your urine color. If your urine is a pale yellow or clear, you are likely well-hydrated. If it's a darker yellow, you may need to increase your fluid intake. Additionally, your body's thirst mechanism is a strong indicator, but on keto, you may need to consciously drink more than usual.

Besides plain water, you can opt for bone broth, which is rich in sodium and potassium, or use a sugar-free electrolyte supplement. Adding a pinch of sea salt to your water or enjoying unsweetened herbal tea can also help replenish minerals and make hydration more interesting.

Yes, you should add more salt to your food on keto, as you are likely consuming less processed food and your kidneys excrete more sodium due to lower insulin levels. Increasing your salt intake helps your body retain necessary fluids and manage electrolyte balance.

Electrolyte supplements can be very beneficial, especially during the initial phase or if you are physically active. They provide a controlled way to replenish the sodium, potassium, and magnesium that are rapidly lost on keto, helping to prevent uncomfortable symptoms and support proper body function.