AbstractBackgroundThe long‐term clinical and biofhemical effects of basal‐bolus insulin treatment with lispro and NPH in dogs with diabetes mellitus are undocumented.ObjectivesTo perform a prospective pilot field study of the long‐term effects of lispro and NPH on clinical signs and serum fructosamine concentrations (SFC) in dogs with diabetes mellitus.MethodsTwelve dogs received combined lispro and NPH insulins treatment twice a day and were examined every 2 weeks for 2 months (visits 1–4), and every 4 weeks for up to 4 additional months (visits 5–8). Clinical signs and SFC were recorded at each visit. Polyuria and polydipsia (PU/PD) were scored as absent (0) or present (1).ResultsMedian (range) PU/PD scores of combined visits 5–8 (0, 0–1) were significantly lower than median scores of combined visits 1–4 (1, 0–1, p = 0.03) and at enrolment (1, 0–1, p = 0.045). Median (range) SFC of combined visits 5–8 (512 mmol/L, 401–974 mmol/L) was significantly lower than SFC of combined visits 1–4 (578 mmol/L, 302–996 mmol/L, p = 0.002) and at enrolment (662 mmol/L, 450–990 mmol/L, p = 0.03). Lispro insulin dose was significantly and negatively, albeit weakly, correlated with SFC concentration during visits 1 through 8 (r = –0.3, p = 0.013). Median duration of follow up was 6 months (range 0.5–6) and most dogs (8, 66.7%) were followed for 6 months. Four dogs withdrew from the study within 0.5–5 months because of documented or suspected hypoglycaemia, short NPH duration or sudden unexplained death. Hypoglycaemia was noted in 6 dogs.ConclusionsLong‐term lispro and NPH combination therapy may improve clinical and biochemical control of some diabetic dogs with comorbidities. Risk of hypoglycaemia should be addressed with close monitoring.