Clinical signs exhibited by diabetic cats reflect the underlying pathological mechanisms of the disease and aid diagnosis. Of course, laboratory tests are needed to confirm diagnosis (see Diagnosis and Management Overview).
Three distinct clinical pictures may develop in cats suffering from diabetes mellitus:
- Uncomplicated diabetes
- Complicated by ketoacidosis
- Hyperosmolar syndrome
Clinical signs of uncomplicated diabetes
The 4 classic clinical signs of diabetes mellitus in cats include:
- Increased susceptibility to infections (eg, urinary tract infections)
Owners may also notice weight loss in affected cats.
Signs of diabetes mellitus complicated by ketoacidosis
If feline diabetes is undetected and left untreated, it will shorten a cat’s lifespan. A dangerous, sometimes fatal metabolic acidosis or diabetic ketoacidosis (DKA) may develop. In untreated diabetic cats, excessive ketones are produced, resulting in ketonuria and DKA accompanied by electrolyte imbalances. Ketoacidosis is a serious condition that can ultimately lead to an acidotic coma and death.
In addition to the classic clinical signs of diabetes, cats affected by DKA may present with:
- Loss of appetite
- Lethargy and depression
- Collapse or coma
Signs of hyperosmolar syndrome
Hyperosmolar syndrome is an uncommon complication of untreated diabetes mellitus. In animals in which target tissue resistance to insulin plays a role in the disease, insulin levels can be elevated. In these cases, ketosis is suppressed and plasma glucose concentrations can become very high. Hyperosmolar syndrome represents an emergency situation. Affected cats will become progressively weaker, anorexic, lethargic, and drink less. Ultimately, blood glucose levels become so high that osmosis shifts water from brain cells and coma results.