It very well could be....first and foremost, get him/her to your vet immediately for full blood profiling and complete urinalysis....this will also help to rule out diabetes, another potential concern.
My Doberman had the same symptoms last summer and in her case, it was hepatitis. She was treated with antibiotics and has since made a very slow but complete recovery.
They did a complete work-up in the vet's office. Good luck....I hope it's nothing too serious.
When a dog is drinking alot of water and urinating excessively it's best to get your dog to the Vet as soon as possible to find out what is going on. Once you know what is causing the symptoms you'll also know what sort of treatment is needed.
