When you feel thirsty, your body is already sending out a dehydration warning. Drinking water may seem simple, but it plays a vital role in overall health, affecting metabolism, circulation, and detoxification. Yet many people only reach for water when thirst strikes. So when should you drink water, how much do you really need, and what kind of water is best?
Surgeon Dr Hsieh Yu-Hsuan, who works in a high-pressure medical environment, says he never waits until he feels thirsty to drink water. Despite a busy schedule filled with consultations and surgeries, he makes it a habit to drink water whenever he has a short break. He tends to drink more water in the morning, reduces intake in the afternoon and evening, and increases hydration before, during, and after exercise.
How Much Water Should You Drink Daily?
The human body is made up of about 70% water, which is essential for blood circulation, temperature regulation, metabolism, and digestion. Doctors recommend estimating daily water needs using a simple formula: body weight multiplied by 30. For example, a person weighing 66kg needs about 1,980ml of water per day. An additional 300 to 500ml should be added to compensate for water loss through sweat and evaporation. More water is needed during hot weather, exercise, fever, or digestive discomfort.
However, many people still wait until they feel thirsty. Nephrology specialist Dr Chiang Heng-Pin warns that thirst is already a sign of dehydration, indicating that the body has lost about 1–2% of its water. Another indicator is urine colour. Family physician Dr Shen Wei-Chen says healthy urine should be light yellow and clear; darker or orange-coloured urine suggests insufficient hydration.
Can Coffee, Tea, or Soft Drinks Replace Water?
Urologist Dr Wen Chen-Yueh stresses that plain water remains the best source of hydration. Unsweetened lemon water or plain sparkling water are acceptable alternatives. While beverages like coffee, tea, and soft drinks contain water, their caffeine and sugar content can place extra strain on the body if consumed excessively. Sugary drinks, in particular, should be avoided.
Hydration During Exercise Requires Planning
Hydration strategies should vary depending on activity levels. Nutrition expert Dr Liao Yi-Ching from Chung Shan Medical University explains that for short, low-intensity exercise in cool environments, drinking according to thirst is sufficient. However, during high-intensity workouts lasting over 90 minutes, especially in hot conditions, hydration should be planned in advance. Both dehydration and overhydration can be dangerous, potentially leading to low sodium levels, rapid heartbeat, overheating, or heat exhaustion.
Drinking Too Little Water Raises Kidney Stone Risk
Dietitian Huang Tai-Chieh from Kaohsiung Medical University Hospital points out that water helps transport nutrients and remove waste from the body. Long-term insufficient water intake may increase the risk of kidney stones and other metabolic issues.
Special caution is advised for elderly individuals and patients with heart, kidney, or liver disease. Their water intake should be adjusted according to medical advice to avoid complications from drinking too much or too little.
Although drinking water seems simple, doing it correctly is essential for good health. Experts recommend developing the habit of drinking small amounts of water regularly throughout the day. It is beneficial to drink more water in the morning or when thirsty, but excessive water intake after dinner should be avoided to prevent sleep disturbances.
