Practical Monitoring of the Diabetic Cat: Clinical Assessment, Glucose Monitoring, and Treatment Response

Effective management of feline diabetes mellitus depends not only on selecting the appropriate therapy but also on systematic monitoring that guides treatment adjustments over time. Monitoring should evaluate the cat as a whole rather than relying on a single laboratory value. Clinical response, glucose trends, glycated proteins, and caregiver observations all contribute to determining whether treatment goals are being achieved safely. An individualized monitoring strategy also helps identify diabetic remission, detect complications early, and maintain long-term glycaemic control. 

Clinical Assessment Remains the Foundation¹ 

Every follow-up evaluation should begin with assessment of the cat's clinical status. Improvement in polyuria, polydipsia, polyphagia, body weight, activity level, grooming behaviour, and overall quality of life provides valuable evidence that treatment is effective. Conversely, recurrence of clinical signs may indicate inadequate glycaemic control, diabetic relapse, insulin resistance, or development of concurrent disease. 

Regular measurement of body weight, body condition score (BCS), and muscle condition score should form part of every reassessment. Changes in these parameters often provide earlier clues to treatment response than glucose measurements alone. Monitoring should also include evaluation for hypoglycaemia, diabetic neuropathy, diabetic ketoacidosis (DKA), euglycaemic DKA in appropriate patients, and newly emerging concurrent diseases that may alter insulin requirements or treatment response. 

Continuous Glucose Monitoring: A Practical Tool for Modern Diabetes Care 

Continuous glucose monitoring (CGM) has transformed monitoring of diabetic cats by allowing almost continuous measurement of interstitial glucose concentrations over several consecutive days without repeated venepuncture. The guideline recommends CGM as an effective tool for insulin dose titration from diagnosis until stabilisation or diabetic remission is achieved. Once stable control has been established, the device may be used continuously, every 2–3 months, whenever changes in insulin dosage are required, or when relapse, hypoglycaemia, or increased glycaemic variability is suspected^1,2,3,4,5. 

CGM offers several practical advantages in everyday practice: 

• Provides detailed information on glucose trends and glycaemic variability over multiple days. 

• Detects hypoglycaemic episodes that may be missed with intermittent sampling. 

• Improves assessment of minimum and maximum glucose concentrations. 

• Allows clinicians to review glucose reports over several days using platforms such as LibreView to evaluate overall glycaemic control rather than isolated readings.136–141 

Despite these advantages, clinicians should interpret CGM results cautiously in the hypoglycaemic range because interstitial glucose concentrations may underestimate or overestimate blood glucose values at very low concentrations. Reduced sensor lifespan, typically 5.5–10 days, should also be discussed with caregivers before initiating monitoring^1,2,3,4,5. 

Home Blood Glucose Monitoring and Glycated Proteins 

Home blood glucose (BG) monitoring remains a valuable alternative, particularly for caregivers who are comfortable performing glucose measurements. During the initial phase of treatment, BG curves are generally recommended once weekly. Following stabilisation, monitoring frequency can gradually decrease to approximately every 3–4 weeks. Measurements are typically obtained before the morning insulin injection and every 2 hours until the evening dose, with longer monitoring periods required if the glucose nadir is not identified. 

Compared with CGM, home BG monitoring provides more accurate measurements in the normal and low glucose ranges but offers less information regarding glycaemic variability and may fail to detect intermittent hypoglycaemic episodes^6,7. 

Serum fructosamine concentrations remain an important adjunct for assessing average glycaemic control over the preceding 7–10 days. Because fructosamine reflects overall glucose exposure rather than short-term fluctuations, it complements but does not replace clinical assessment or glucose monitoring. Importantly, episodic hypoglycaemia cannot be excluded solely on the basis of glycated protein measurements¹. 

Monitoring Treatment Response 

Monitoring should focus on meaningful clinical outcomes rather than isolated numerical targets. Decisions regarding dose adjustment should integrate improvement in clinical signs, glucose patterns, body weight, fructosamine concentrations where appropriate, and caregiver observations. 

Persistently normal glucose concentrations, absence of glucosuria, normal fructosamine concentrations, or episodes of hypoglycaemia may indicate declining insulin requirements and should prompt gradual insulin dose reduction while carefully monitoring for recurrence of clinical signs. Likewise, worsening glycaemic control should trigger reassessment for concurrent disease, treatment adherence, insulin resistance, or diabetic relapse. 

Practical Clinical Insights 

Successful monitoring combines careful clinical assessment with appropriate objective measurements. Continuous glucose monitoring provides the most comprehensive evaluation of glycaemic patterns and is particularly valuable during insulin titration and when remission or glycaemic variability is suspected. Home blood glucose monitoring and serum fructosamine remain valuable complementary tools, particularly when interpreted alongside changes in clinical signs and body weight. Rather than reacting to isolated glucose values, veterinarians should evaluate overall treatment response and individualize monitoring schedules to suit both the patient and the caregiver, ensuring safe and effective long-term diabetes management. 

References 

1. Taylor S, Cannon M, Church D, Fleeman L, Fracassi F, Gilor C, Mott J, Niessen S. 2025 iCatCare consensus guidelines on the diagnosis and management of diabetes mellitus in cats. Journal of feline medicine and surgery. 2025 Nov;27(11):1098612X251399103. https://journals.sagepub.com/doi/pdf/10.1177/1098612X251399103 

2. Shea EK, Hess RS. Validation of a flash glucose monitoring system in outpatient diabetic cats. Journal of veterinary internal medicine. 2021 Jul;35(4):1703-12. https://academic.oup.com/jvim/article-pdf/35/4/1703/66651897/jvim16216.pdf 

3. Knies M, Teske E, Kooistra H. Evaluation of the FreeStyle Libre, a flash glucose monitoring system, in client-owned cats with diabetes mellitus. Journal of Feline Medicine and Surgery. 2022 Aug;24(8):e223-31. https://journals.sagepub.com/doi/pdf/10.1177/1098612X221104051 

4. Berg AS, Crews CD, Adin C, Alfonso‐Castro A, Hill SB, Mott J, Gilor C. Assessment of the FreeStyle Libre 2 interstitial glucose monitor in hypo‐and euglycemic cats. Journal of Veterinary Internal Medicine. 2023 Sep;37(5):1703-9. https://onlinelibrary.wiley.com/doi/pdf/10.1111/jvim.16820 

5. Tardo AM, Crews C, Mott J, Porter LT, Adin C, Gilor C. Accuracy of the Freestyle Libre 3 continuous glucose monitoring system in hypo-and euglycemic cats. Journal of Veterinary Internal Medicine. 2025 Mar;39(2):jvim70048. https://academic.oup.com/jvim/article-pdf/39/2/jvim70048/66652309/jvim70048.pdf 

6. Niessen SJ, Powney S, Guitian J, Niessen AP, Pion PD, Shaw JA, Church DB. Evaluation of a quality-of-life tool for cats with diabetes mellitus. Journal of Veterinary Internal Medicine. 2010 Sep;24(5):1098-105. https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1939-1676.2010.0579.x 

7. Re M, Del Baldo F, Tardo AM, Fracassi F. Monitoring of diabetes mellitus using the flash glucose monitoring system: the owners’ point of view. Veterinary Sciences. 2023 Mar 7;10(3):203. https://www.mdpi.com/2306-7381/10/3/203