Excessive Hydration in Infants

Excessive Hydration (Hyperhydration) in Infants

Hyperhydration, or water intoxication, is a rare but potentially dangerous condition that occurs when an excess of water accumulates in an infant’s body, leading to a critical drop in blood sodium concentration. In children under one year of age, it most often results from caregiving errors.

Why does hyperhydration occur in infants?

An infant’s kidneys are still immature and cannot excrete large volumes of water as efficiently as adult kidneys. The sources of excess fluid may include:

• Improper dilution of infant formula: Parents, trying to save money, add too much water.
• Excessive offering of water: Giving a large amount of plain water to a child under 6 months. Up to this age, a breast‑fed or formula‑fed infant does not need additional water. More details are in the blog "When and how to offer water to an infant?".
• Improper rehydration during illness: Using plain water instead of rehydration solutions for diarrhea.

Mechanism of injury

The main danger, as with general hyperhydration, is the development of hyponatremia (low sodium level) and cerebral edema. This leads to neurological symptoms: irritability, lethargy, vomiting, and in severe cases — seizures. This condition requires immediate medical attention and correction of the electrolyte balance.