Can drinking too much water at night cause puffy eyes the next day?

Drinking excessive water in the evening may cause eye swelling the following day.

Eye swelling primarily results from the loose subcutaneous tissue of the eyelids. During sleep, physical activity decreases, and if large amounts of water are consumed in the evening, the blood absorbs excess fluid, leading to hemodilution and a consequent reduction in plasma osmotic pressure. As a result, fluid shifts from the intravascular space into the interstitial tissues—particularly the eyelids—where the subcutaneous soft tissue is especially loose and thus more prone to fluid accumulation, causing periorbital edema. In patients with kidney disease—such as interstitial nephritis or glomerulonephritis—excessive water intake at night may impair renal water metabolism, potentially resulting in periorbital edema the next day, possibly accompanied by lower-limb edema or other symptoms.

To minimize swelling, it is advisable to avoid drinking large quantities of water before bedtime, as this may cause nocturia and disrupt sleep quality. If eye swelling persists for an extended period after excessive water intake in the evening, prompt medical evaluation is recommended. Appropriate diagnostic tests should be performed, and treatment should be tailored according to the underlying cause.