Answer: The short answer is yes- unless he is vomiting.
In every case accept one cats drink to replace water which has already been lost from the body. If you do not allow them to make up for the loss, whether it has arisen normally or as a result of disease, they will become dehydrated. A total lack of water will cause problem much more rapidly then the lack of any other component of the diet such as protein or fat. Therefore a bowl of clean water must always be available.
Animals which continually have an excessive thirst are almost certainly suffering from some disorder that should be investigated by your vet. In these disorders the body loss water more rapidly then usual, i.e. cannot retain it, so that the cat produce more urine then usual. The cat often has difficulty in holding all this urine in the bladder over a long period of time, e.g. overnight, so that it frequently goes out to urinate or uses its litter box. Some owners mistakenly think that the answer to this problem is to withhold water from the cat, not realizing that they prevent the animal making good the heavy losses which have occurred and provoke the onset of dehydration, thereby the making the illness worse. If the cat has an increased thirst always take it for veterinary attention.
Only withhold water from the animal if it vomits. Vomiting is most often due to some irritation of the lining of the stomach which causes the stomach contents to be rejected. The loss of the water and salts in the vomit makes the animal very thirsty so that it wants to drink, but the presence of water in the stomach provokes further vomiting. In this way a cycle of drinking and vomiting can develop which may lead to serve dehydration and collapse.
