Back in November our cat (approx 3 years old) was diagnosed with urinary crystals. So we changed his diet to Purina urinary st/ox both wet and dry. He stopped peeing in our clothes and had been his happy usual self since then; however, he has lost a significant amount of weight. I can see his waist line and he looks too thin. We did just have him dewormed since he enjoys hunting. He is happy, eats well, drinks wells and I believe he is eliminating ok (although he does most of that outside). Its just the weight loss. Could his food be causing it? I am on maternity leave and unable to pay for the blood work that I know the vet will want. Any suggestions?