Ferrets are obligate carnivores. Cat food does not provide the protein or fat content needed by the ferret's metabolism. High-quality kitten food can suffice if ferret-specific kibble cannot be found, however many low quality foods are not appropriate. When reading the label, the first 3 ingredients should be meat-based, as ferrets cannot properly digest the cereal fillers used in cheaper cat and kitten foods. Ferret food should contain between 32–38% protein and between 15–20% fat. (The protein source of ferret food should be meat based, not soy or whey.) While a high protein content is absolutely essential a protein content above 38% can sometimes lead to kidney stones and urinary obstructions in older ferrets. Ferrets usually have fondness for sweets such as raisins and peanut butter, but such treats should be given sparingly, as even a small amount of sugar can increase chances of insulinoma and adrenal failure. While plant products can provide ferrets with some additional micro-nutrients and dietary variability, due to their relatively short gastro-intestinal tract they can not derive much energy out of them, and for that reason they should only be used as supplement, not replacement, for their regular diet.