Hypohydration

Hypohydration is a state where the body’s total water content is reduced below normal because fluid losses exceed intake. It describes the uncompensated deficit of body water rather than the process of losing fluid. When more water is lost through sweat, breathing and urine than replaced, the body cannot regulate temperature and blood circulation as efficiently.

Impact on performance and health

Hypohydration occurs when the body’s water loss exceeds fluid intake. In exercise contexts, sweat rates can range from about 0.5–2 litres per hour and a loss of as little as 2 % of body mass impairs endurance and cognitive performance. When the body is under‑hydrated, blood volume falls, making it harder for the heart to deliver oxygen and remove heat. The body reduces skin blood flow and sweat rate to conserve water, which increases core temperature. Early signs include thirst, dry mouth, decreased urine output and fatigue. More severe hypohydration may lead to dizziness, confusion or heat exhaustion.

Practical tips and real‑world insights

Athletes can monitor hydration by tracking body weight before and after exercise and observing urine colour. A body mass decrease of more than about 2 % indicates significant water loss. To prevent hypohydration, drink about 500 ml of fluid two to three hours before training or competition and then consume roughly 150–250 ml every 15‑20 minutes during exercise. After activity, aim to replace 150 % of the weight lost through sweat using water or drinks containing sodium to promote fluid retention and restore electrolyte balance. Adjust intake to personal sweat rate, environmental conditions and individual tolerance.

In summary, hypohydration describes the state of being under‑hydrated due to uncompensated body water loss. Even mild deficits can affect physical and cognitive performance, so proactive fluid intake and monitoring of sweat losses are essential. Drinking enough before, during and after exercise helps maintain blood volume, regulate temperature and support recovery.

Related Terms: Dehydration, Euhydration, Hyperhydration, Rehydration, Sweat rate