The simple answer is: It depends. The amount of water you need depends on your age, weight, diet, activity level, state of health, and the climate in which you live.

Chances are you’ve heard that you must down eight glasses of water per day, but you may not necessarily need to drink that much. In fact, in 2004 the Institute of Medicine amended its guidelines on fluid consumption. Instead of recommending that people drink eight glasses of water a day, it now recommends that people generally be guided by their level of thirst when deciding how much to drink.

There are exceptions, however. Infants, children, the elderly, pregnant or breastfeeding women, people who are ill, those undertaking strenuous exercise or anyone out in hot weather, are advised to not rely solely on their level of thirst as an indicator of whether they need to drink more water. In all of the above situations, it is advisable to ensure fluid intake is sufficient and to not wait until a thirst develops before drinking more fluid.

So, listen to your body! If you’re feeling thirsty, you need to drink. If you’ve let yourself become super-thirsty, you may already be a little dehydrated. Have a glass of water.

Pay attention to your body’s signals. Check the color of your urine. Ideally it should be pale yellow, almost clear. If it is and you’re producing about one to two liters of urine per day and going to the bathroom between around seven to twelve times per day,  you’re likely drinking enough fluids. If however, your urine is dark in color and has a strong odor, and you go to the bathroom infrequently, you may need to drink more fluids.

Also, if you notice your thirst and urine level have increased, consider visiting a medical professional. Some medical conditions, such as diabetes, increase a person’s thirst. If in doubt, get checked out.