Drinking two liters of water a day “to cleanse the kidneys” has become an unofficial rule, repeated in gyms and at the office. However, figures given to Spanish public television RTVE show that at rest, a healthy adult needs less for their kidneys to properly eliminate toxins, without risking dehydration.
Guest in 2025 on the health show Saber VivirDr. Borja Quiroga, a Spanish nephrologist, set the record straight. He first recalls that “the kidney has the ability to concentrate and dilute urine“, explains Quiroga. Then he details: “If we drink a lot…the kidney actually dilutes the urine. Urine is transparent. This only reflects that the kidney is working well because it is able to dilute urine, but it is neither improving nor deteriorating“, he adds.
The calculation of Dr. Borja Quiroga
For him, the real threat comes from the lack of water. “This is even worse, because the kidney, as a purification station for toxins from the body, needs a minimum quantity of water to precisely eliminate these wastes.“, he warns. He therefore quantified this threshold: “To eliminate toxins day by day, and I generalize, no one takes it as something fixed, half a liter of water per day“, he explains.
“Under normal conditions, simply by being alive, we lose a little water through the skin, through perspiration, through breathing, without realizing it. This is called insensible losses“, explains Borja Quiroga.
They represent approximately 700 to 800 milliliters per day. “In a basal situation, without sport, without digestive losses, without sweating a lot, the minimum quantity of water for healthy people is around 1.2 liters or 1.3 liters“, he concludes. Several health articles present this threshold as a total water intake: water, drinks and water portion of food.
Drinking more does not make the kidneys “cleaner”
In a person with healthy kidneys, going well beyond this minimum does not make them function better. The excess is simply expelled in clearer urine, which is often falsely reassuring. On the other hand, at extreme volumes, around 18 to 20 liters daily, a serious disorder such as hyponatremia can appear.
The figure of 1.2 to 1.3 liters therefore remains a basis for a calm day, at moderate temperature. The needs increase as soon as we sweat more, with sport, heat, fever or diarrhea, as recalled by L’Internaute or Parole de Mamans. There is no need to count each sip: the body’s signals guide you.
How to check that you are drinking enough for your kidneys?
For everyday life, the doctors in the articles in L’Internaute remind us of two simple benchmarks: thirst and the color of urine. Very dark or amber urine suggests a lack of water, while pale yellow urine is reassuring.
In seniors or heart and kidney patients, these benchmarks become less reliable, hence the need to follow the doctor’s advice.