Reverse osmosis water (RO water) itself is usually not directly harmful to the kidneys. Reverse osmosis technology can effectively remove most impurities in water, including bacteria, viruses, heavy metals, and chemical contaminants, so the water it produces is very pure. However, this pure water also removes many minerals that are present in natural water, such as calcium, magnesium, and potassium. For most healthy adults, drinking demineralized water (such as reverse osmosis water) does not pose a direct threat to health, as a balanced diet can usually replenish these minerals. However, if there are specific health problems, such as kidney disease, it is best to consult a medical professional before changing your drinking habits. The doctor may recommend that such patients ensure that the water they drink contains enough minerals, or make up for the lack of these minerals through diet and supplements.