Confirm the diagnosis from the whole pattern: a dog with compatible polyuria, polydipsia, polyphagia, weight loss, or cataract development plus concurrent persistent hyperglycemia and glucosuria has clinical diabetes mellitus. Record body weight and condition, hydration, diet and treats, medications, reproductive status, chemistry, urinalysis, ketone status, CBC and electrolytes as appropriate. Add quantitative urine culture when urinary signs or an active sediment support infection rather than treating subclinical bacteriuria automatically. Reserve pancreas-specific lipase and thyroid testing for supporting clinical findings; untreated diabetes can suppress total T4. In an intact systemically ill or ketonuric female, actively consider pyometra. Next separate four lanes. A stable hydrated dog that is eating can enter routine insulin planning. Ketonuria alone increases concern but does not establish DKA; assess systemic illness, hydration, blood beta-hydroxybutyrate, electrolytes, and acid-base status. Diabetes with systemic illness, ketosis, and metabolic acidosis is DKA and requires hospital care, fluids, electrolyte correction, monitored short-acting insulin, serial glucose and ketone assessment, and treatment of the precipitating disorder. Suspected hypoglycemia is a separate emergency lane. For a conscious mildly affected dog, offer a small carbohydrate-containing meal and obtain veterinary care. For a poorly responsive, tremoring, collapsing, or unsafe-to-feed dog, place a small amount of concentrated sugar on the cheek-side gingiva without forcing liquid or putting fingers deep in the mouth, then seek emergency care; seizures are an emergency. Do not increase insulin after suspected hypoglycemia. For stable diabetes, choose a clinician-calculated plan. Porcine lente U-40 and NPH U-100 are representative intermediate options commonly given every 12 hours. Match U-40 and U-100 products to the correct syringe or compatible pen and confirm caregiver technique. For a prescribed bolus or intermediate-insulin plan, the current AAHA meal branch gives the full dose after at least half of the meal is eaten, one-half of the usual dose when less than half is eaten, and veterinary contact if inadequate intake continues for two consecutive meals. Keep this formulation-specific and written; never generalize it to every insulin or encourage improvised adjustment. Newer basal insulins can help selected dogs with unpredictable appetite, but require formulation-specific dosing and close glucose monitoring. Use a complete, balanced, palatable, consistent diet matched to body condition and comorbid disease. In an intact female, diestrus-associated resistance makes ovariohysterectomy part of the plan after stabilization, with close insulin reassessment as resistance falls. Judge control by clinical signs, weight, quality of life, and avoidance of hypoglycemia. Obtain a curve or CGM assessment about 5–14 days after starting insulin or changing a dose, when signs recur, or when hypoglycemia is suspected. Confirm an unexpected low sensor result with a veterinary-calibrated meter when signs do not match. Fructosamine supports a trend but does not show nadir or duration; urine glucose and an isolated high spot value are not routine stand-alone dose commands. A low nadir followed by rebound hyperglycemia should lead to insulin reduction and time-action reassessment, not automatic escalation. When control is poor, verify insulin identity, concentration, matching device, handling, storage, injection, meal intake, schedule, adherence, and glucose time action before investigating infection, pancreatitis, dental disease, hyperadrenocorticism, renal disease, obesity, medications, and reproductive hormones. New ocular opacity, vision loss, ocular pain, anorexia, vomiting, dehydration, ketones, or altered mentation reopens urgent complication or decompensation pathways.