You have probably heard the old adage, “Drink eight glasses of water per day.” While water consumption is important in preventing dehydration and for overall health, there is no magic number for how much water you should drink per day. Plus, that figure doesn’t even take water from other sources into account. Many foods that people eat contain some water, and certain fruits like watermelon are nearly 100% water by weight.

Water consumption, like many other aspects of health, occurs on a spectrum. What is adequate for one person might not be adequate for another. If you exercise, you will need to drink more water to stay hydrated. People also need to increase their water intake in hot, humid weather, or when pregnant or breastfeeding.

People who suffer from certain medical conditions such as congestive heart failure may have to restrict fluids, along with their  salt intake. Excessive production of ADH (antidiuretic hormone) sometime occurs after head trauma, or in the case of certain cancers. Because of difficulties with eliminating water, these people will dilute their sodium and need to restrict intake of water. Your doctor will advise you if you need to restrict water intake. Excessive water intake (as in certain mental illnesses) can cause very low sodium, water intoxication, and cerebral edema with serious neurological consequences and, in extreme cases, even death.

Aside from medical conditions that require limited water intake, water is important for health. It is by far the healthiest beverage you can drink, since it avoids the added sugars and calories found in popular drinks like soda. Your body consists of about 60% water by weight. Every cell needs water to function properly. It helps with functions such as temperature regulation, protecting sensitive tissues, and the elimination of wastes through sweat and urination.

The easiest way to tell if you are drinking enough water is to pay attention to your body. If you feel thirsty, you’re probably dehydrated and should take a drink. If you are drinking enough water to remain hydrated, your urine should regularly be light yellow and without a strong smell.