If your cat starts drinking much more water than usual, this is not standard quirky cat behavior. Take your cat to the vet. Increased thirst could portend such maladies as kidney failure, diabetes, and hyperthyroidism. Trust me on this.
Today, with seemingly little warning, my cat Marcelle passed away, a victim of kidney failure.
I got Marcelle when she was two years old. Born in Uzbekistan and raised in France, she was shy yet talkative, the complete opposite of Marcel Marceau. She was easily frightened and uninterested in toys — and sometimes, easily frightened by toys — and she looked like a miniature Maine coon, with a tiny bend at the end of her tail where it must've been caught in a door when she was a kitten.She'd greet me when I got home. She'd have conversations with us by meowing in response to whatever we said. Like most cats, she had a knack for interposing herself between reader and book, or writer and computer. When I first got her, she hid under the floorboards and meowed me awake every morning at 4:30. She'd then rub her face against my chin.
She was the sweetest cat I've ever known.
About two months ago, Marcelle started begging for water every morning. We'd fill the upstairs sink for her, or a small bowl, and she'd lap away at it as if she hadn't had a drink in weeks. It was odd behavior, but she was a cat of many quirks, and everything else seemed normal so we thought nothing of it. We figured our dog, Sonya, had been drinking her water downstairs (she did that sometimes), or chasing her back upstairs (she did that often). Besides, the air in the house did get dry in late autumn.
A few weeks ago, Marcelle began hiding in one of our box springs, and vomited up bile a few times in a matter of days. She'd done both things before (there was a hole in the box spring, and cats vomit), so again we weren't worried. Character quirks, that's all. Just a phase. She visited with us less often, but when she did come out, she was as affectionate (or as likely to run from the Sonya) as she'd always been.
We only realized something was wrong in the past few days. As a small cat, she'd always had slightly bony hips, but now we could feel her ribs and spine. And though Sonya sometimes ate her food, we now realized Marcelle was barely eating, barely drinking. She'd lost two pounds, or more than ¼ of her total weight. Yet, apart from this, she was still acting like herself.
The vet did all he could, but it turned out she was already in Stage IV of chronic renal failure, and the end came much quicker than any of us expected. By this afternoon, at the tender age of nine, our dear Marcelle was gone. We never even got the chance to say goodbye.
And it was all my fault.
You may think I'm being too hard on myself, but I should have sensed something was wrong when Marcelle kept begging for water. She had many quirks, but she always repeated them. Never had she consumed water at such a pace before. Never had she kept herself hidden from me for so much of the day.
Kidney failure can be managed if it's caught early enough. All I had to do was Google "cat drinking a lot of water," and I'd have understood. I could have saved her. I could have given her many more happy years of meowed conversations and frightening toys.
I'm so sorry, Marcelle. So so sorry. I didn't know.
But at least now, others will.

Marcelle
2001-2010
Goodbye, Marcelle. We miss you dearly.