How do I select an insulin type and titrate the dose for a newly diagnosed diabetic cat?

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For a newly diagnosed diabetic cat, glargine (Lantus) is the first-line insulin, started at 0.5 U/kg q12h if blood glucose (BG) is >360 mg/dL or 0.25 U/kg q12h if BG is <360 mg/dL, not to exceed 2 U per cat q12h regardless of body size. Protamine zinc insulin (PZI; ProZinc) is an acceptable alternative at 1–2 U per cat q12h. Both are dosed based on estimated ideal body weight, not actual weight. 1 On the first day of insulin treatment, monitoring is at the clinician's discretion and is performed solely to detect hypoglycemia — the dose must not be increased based on first-day BG values. If monitoring is elected, measure BG every 2–4 hours for cats on PZI and every 4 hours for cats on glargine, for 10–12 hours following administration. If BG falls below 150 mg/dL at any point during that window, reduce the insulin dose by 50%. 1 After the first day, the cat is managed as an outpatient with a scheduled recheck in 7–14 days. Immediate re-evaluation is warranted if clinical signs of hypoglycemia appear or if lethargy, anorexia, or vomiting develops. 1 Long-term dose titration targets a maintenance dose of approximately 0.5 U/kg q12h, with an acceptable range of 0.2–0.8 U/kg q12h. A ±2-hour window on each side of the 12-hour dosing interval and occasional missed doses are considered acceptable. 1 Adding the glucagon-like peptide-1 (GLP-1) analogue exenatide extended release (EER) at 200 µg/kg SC once weekly to glargine and a low-carbohydrate diet reduces glycemic variability and improves remission rates in newly diagnosed diabetic cats. Cats achieving remission on this combination had lower glycemic variability compared to those without remission. 3 | Insulin | Starting Dose | Max Starting Dose | Maintenance Range | Monitoring Interval (Day 1) | |---|---|---|---|---| | Glargine (Lantus) | 0.5 U/kg q12h (BG >360 mg/dL) or 0.25 U/kg q12h (BG <360 mg/dL) | 2 U/cat q12h | 0.2–0.8 U/kg q12h | q4h for 10–12 hr | | PZI (ProZinc) | 1–2 U/cat q12h | 2 U/cat q12h | 0.2–0.8 U/kg q1