Dr Lim Lee Guan says a person could lose up to 10 litres of water a day through sweat. The actual sweat rate depends on a person’s metabolic rate, or the amount of energy expended by the body in staying alive.

He suggests multiplying your body weight in kilograms by 30 and 40 to get an estimate of how many millilitres of water you require a day. A 60kg adult would thus require at least 1.8 to 2.4 litres of water a day.

He notes that both Singapore’s Health Promotion Board and Britain’s National Health Service recommend drinkingeight glasses of water, or two litres, a day. This amount includes water from food and liquids such as low-fat milk and sugar-free drinks.

However, people with medical conditions such as heart failure, kidney failure and liver failure will need to consult their doctors for an individual recommendation of what to drink and eat, as they are at risk of a condition known as fluid overload.

“This can lead to fluid in the lungs causing breathing difficulty, fluid in the abdomen causing abdominal distension and fluid in the limbs causing swollen limbs,” he says. “In addition to fluid restriction, salt restriction is usually also required. The doctor will advise on the restriction needed based on the individual’s condition.”