Diabetes Mellitus

Feline diabetes mellitus is Type II diabetes in the vast majority of cases — insulin resistance with relative insulin deficiency. Obesity is the primary risk factor.

Clinical signs: PU/PD, polyphagia, weight loss, lethargy, poor coat quality, plantigrade stance (peripheral neuropathy).

Diagnosis:

• Hyperglycemia: > 200–250 mg/dL (cats have higher stress hyperglycemia threshold than dogs)
• Glucosuria: Confirms renal threshold exceeded
• Fructosamine: > 350 mcmol/L confirms chronic hyperglycemia (not stress-induced)

Differentiate from stress hyperglycemia: In-hospital glucose may be > 300 mg/dL from stress alone. Fructosamine or home glucose monitoring confirms true diabetes.

Insulin:

• Glargine (Lantus): 0.25–0.5 U/kg SC q12h; first-line; best remission rates
• PZI (ProZinc): 1–3 U/cat SC q12h; veterinary-approved for cats
• Detemir: Alternative long-acting
• Avoid Vetsulin (canine-specific, shorter duration in cats)

Diet:

• Low-carbohydrate, high-protein diet (Hill's m/d, Purina DM, Royal Canin Glycobalance)
• Canned preferred over dry (lower carbs, higher moisture)

Monitoring:

• Serial blood glucose curves (q1-2 weeks initially)
• Target nadir: 100–150 mg/dL
• Fructosamine q4-6 weeks
• Home glucose monitoring (ear prick) increasingly used

Diabetic ketoacidosis (DKA): See DKA topic. Emergency — dehydration, electrolyte abnormalities, ketonuria/ketonemia.

Peripheral neuropathy: Plantigrade stance, hind limb weakness. Reversible with glycemic control.

Infections: UTIs (glucosuria predisposes), skin infections, periodontal disease.

Remission:

• 20–40% of cats achieve diabetic remission with glargine + low-carb diet
• Highest in cats treated within 6 months of diagnosis
• Remission defined as euglycemia without insulin for > 4 weeks
• Continue low-carb diet lifelong; remission can relapse