So, considering that you've gone through DKA twice in a row, I wanted to talk about possible causes or risk factors. Basically, the ketones form due to fat breakdown in the body which can happen for multiple reasons. It's helpful to remember that while insulin lowers BS, it also allows cells to use glucose for energy. Without insulin, cells starve. Starving cells tell the body to burn fat so they can use ketones for energy (dangerous if this occurs for more than a little bit).
Infection: Infection causes the body to need more insulin to heal, if more insulin isn't available, the body will try to burn fat. Common infections are UTI, bowel parasites or infections, viral infections such as feline herpes, etc.
Too low calorie intake: You should look at a cat body chart and see where your cat falls as far as weight. Basically, if you can see the outline of the shoulder blades, your cat may be too thin. Any cat that is on the thin side and having issues with BS control or DKA should -NEVER- be restricted in the amount of food they eat. Low body weight makes "brittle diabetes" more of an issue, makes BS harder to control, and predisposes to illness. Also, not all calories are processed the same way, proteins and fats have a complex metabolism that relies on several enzymes that may not be present in certain illnesses. Carbs are a much simpler pathway, and may allow faster weight gain and glucose stabilization in skinny cats. Ultra-low carb diets in skinny cats may lead to DKA if prone.
Chronic Illness: Illnesses that make food hard to absorb should be considered as causes - pancreatitis, liver disease, IBS, bowel lymphoma, diarrhea or constipation, cancer, other GI issues. Also some illnesses cause higher metabolism or calories to burn - hyperthyroid, cancer, heart failure, kidney disease, parasites, etc. These should all be ruled out.
Too low insulin: Insulin is like air - a body always needs it to survive. Without insulin, cells starve, and metabolism goes haywire. The body makes some amount, but it may not be enough to allow the metabolism to remain normal. We -INDIRECTLY- monitor insulins effect on the body through BS tests, but that's not the only function of insulin. When BS is normal to low in response to insulin, there is actually 2 options to keep sugar at good levels - you can either reduce insulin, or increase food. The right choice really depends on the situation. Same goes for high blood sugars - you can either reduce food or increase insulin. It's good to think about the results of the choices in relation to the kitty's needs (ie encouragement or prevention of weight gain).
Dehydration: If chronic kidney disease, diarrhea, or heart failure are issues, dehydration can be the initial trigger. Balancing hydration in complex kitties really requires vet monitoring/lab monitoring.