What condition is caused by not having enough fluid in the body?

Dehydration is the condition that occurs when the body loses more fluids than it takes in, leading to a deficit in the amount of water necessary for it to function properly. The human body relies on a certain level of hydration to maintain bodily functions such as regulating temperature, transporting nutrients, and removing waste. When fluid levels drop, various symptoms may arise, including thirst, dry mouth, fatigue, and in more severe cases, confusion or dizziness.

The other conditions mentioned do not directly pertain to a lack of fluids. Hyperhydration refers to an excess of fluids in the body, which can lead to a different set of health issues. Hypertension is related to high blood pressure, which does not specifically involve fluid deficiency but rather the force of blood against artery walls. Malnutrition, while it can involve a deficiency of nutrients including water, is primarily characterized by inadequate intake of essential vitamins and minerals rather than fluids alone. Thus, dehydration is distinctly defined by insufficient fluid levels within the body.