Drinking water flushes the kidneys

Drinking recommendations from nephrologists

The heat wave has Germany firmly under control and is particularly straining the elderly. "In the last few days we have seen many dehydration-related emergencies in the clinics - such as circulatory problems, palpitations and acute kidney failure," explains Prof. Dr. Jan C. Galle, press spokesman for the German Society for Nephrology (DGfN). “Older people in particular should drink enough. 1.5 to 2 liters a day is normal, if you sweat heavily it can be half a liter more. ”However, drinking much more fluid is of no use. The drinks should also contain enough minerals. Instead of tap water, it is better to drink an apple spritzer or a non-alcoholic beer.

At these temperatures we even work up a sweat without doing much physical activity and lose fluids. If we don't drink enough, it can become a problem. The human body normally needs 1.5 to 2 liters a day, but many people, especially the elderly, are significantly less. At the latest during a heat wave, as we are currently experiencing, this can lead to health complications. The body loses fluids and minerals through sweating. The kidneys can “catch” this for a while - they regulate the body's fluid and electrolyte levels - but sooner or later complications arise.

Frequent consequences of dehydration are poor circulation through to palpitations and fainting. Disturbances of consciousness also occur more often, as do phases of confusion, some people even fall into a coma. Another complication is the occurrence of acute kidney failure: the kidneys refuse to work overnight, hardly any urine is excreted and severe symptoms of poisoning with nausea, vomiting and water retention occur in the body.
If water accumulates in the lungs, it can make breathing difficult and life-threatening. "In the last few days we have seen a lot of dehydration-related emergencies in the clinics - such as circulatory problems, palpitations and acute kidney failure," explains Galle. "We would therefore like to urgently recommend the public to drink enough".


Warning signs that too little was drunk are:

  • if you have to urinate significantly less often and less than usual,
  • if the urine is very dark,
  • when the skin and mucous membranes are dry,
  • if dizziness or a racing heart occurs,
  • when it comes to rapid, otherwise inexplicable weight loss.

Sufficient mineral intake

People who take water tablets (diuretics) to lower blood pressure or treat other illnesses are particularly at risk. Older people are another risk group, "because they often feel much less thirsty than younger people," says the expert.

“In addition to sufficient fluid intake, care should be taken to ensure that there is an adequate intake of minerals, because we also sweat out valuable minerals. Tap water that is carbonated or so-called table water contain relatively few minerals. Mineral water is better - and now and then an apple juice spritzer or a non-alcoholic beer. "

Galle generally advises against lemonades with added sugar, and cola in patients with damaged kidneys. “In addition to the sugar, a second 'poison' is added here. In patients with chronic kidney disease, cola increases the amount of phosphate in the blood, which in turn can accelerate kidney disease. Since many patients are unaware of their mild kidney disease, they risk their kidney health without even knowing it if they drink a lot of cola. "

Volume overloads tend to be rather disadvantageous

However, if you want to avoid dehydration and now think the more you drink the better, you are on the wrong track. In patients with heart or kidney disease, volume overload is usually more of a disadvantage. The opinion that whoever drinks a lot, flushes the kidneys and protects them, is a myth. A randomized controlled study at nine Canadian centers last year showed that increasing the amount of drinking by 1 to 1.5 liters a day over twelve months did not lead to any differences compared to the control group (maintaining the previous amount of drinking) with regard to kidney function (so-called GFR), protein excretion and well-being .

In summary, healthy people should follow the recommendation of 1.5 to 2 liters at normal temperatures and 2 to 3 liters at hot temperatures with regard to drinking quantities. Heart or kidney patients should speak to their doctor; a general recommendation cannot be given for them.



Clark W et al. Effect of Drinking More Water on Kidney Function Decline in Adults with CKD: A Randomized Clinical Trial. ASN 2017, FR-PO1068

Source: DGfN, July 31, 2018: