When you restrict carbohydrates, your body depletes glycogen stores, each gram of which holds 3-4 grams of water. This initial water loss can be 2-5 pounds in the first week. Additionally, lower insulin levels cause the kidneys to excrete more sodium and water, increasing hydration needs.

Plan to drink 20-30% more water than the standard recommendation when on keto, especially during the first 2-4 weeks of adaptation. If your baseline is 2.5 liters, aim for 3-3.25 liters. Also supplement electrolytes — sodium (3-5g), potassium (1-3.5g), and magnesium (300-500mg) daily.

Yes, many 'keto flu' symptoms — headaches, fatigue, dizziness, muscle cramps, and brain fog — are actually caused by dehydration and electrolyte imbalance rather than ketosis itself. Increasing water and electrolyte intake often eliminates or significantly reduces these symptoms within 24-48 hours.