Monitoring Diabetes in Dogs: Clinical Insights on Fructosamine and HbA1c

Diabetes mellitus (DM) is a common endocrine disorder in dogs, requiring careful monitoring to optimize insulin therapy and maintain glycemic control. Among the biochemical tools available for veterinarians, serum fructosamine (SF) and blood hemoglobin A1c (HbA1c) are key markers that provide complementary insights into a dog’s glycemic status^1,2. 

Understanding Glycated Proteins in Canine Diabetes 

Serum fructosamine is a glycated protein formed by the non-enzymatic binding of glucose to serum proteins, primarily albumin. In dogs, SF concentrations reflect the mean blood glucose over the preceding 1–2 weeks, which corresponds approximately to the lifespan of serum albumin¹. SF can be measured quickly, accurately, and economically using the nitroblue tetrazolium reduction method, making it a practical tool for routine clinical evaluation². 

Hemoglobin A1c (HbA1c), on the other hand, represents glycation of hemoglobin in erythrocytes and reflects average glucose concentrations over 2–3 months due to the longer lifespan of canine red blood cells³. HbA1c measurement has historically been underused in dogs, but commercial canine assays, such as A1Care, have made routine clinical testing more accessible¹. 

Clinical Applications of Fructosamine and HbA1c 

Both SF and HbA1c provide valuable information, but their clinical utility differs: 

• Short-term monitoring: SF responds rapidly to changes in insulin therapy, making it ideal for assessing recent glycemic control and adjusting treatment regimens². 

• Long-term monitoring: HbA1c offers insights into chronic glycemic trends, helping veterinarians evaluate long-term disease management². 

Notably, correlation between these markers and blood glucose varies in hyperglycemic dogs, the correlation is substantial for HbA1c and moderate for SF, whereas in normoglycemic dogs, SF and HbA1c may primarily reflect parent molecule concentrations (albumin or hemoglobin) rather than glucose³. 

Limitations and Considerations 

While both markers are clinically useful, certain conditions can affect their accuracy: 

• Serum fructosamine: Levels can be influenced by hypoproteinemia, hyperlipidemia, azotemia, hypothyroidism, and hyperglobulinemia caused by multiple myeloma². 

• HbA1c: Values may be decreased in conditions that shorten erythrocyte lifespan (e.g., hemolytic anemia, blood loss, splenomegaly, pregnancy) or falsely increased in conditions that prolong erythrocyte lifespan (e.g., iron deficiency anemia) or interfere with the assay (e.g., extreme hypertriglyceridemia, hyperbilirubinemia^)2,3. 

These limitations underscore the importance of interpreting SF and HbA1c results in the context of clinical signs, comorbidities, and blood glucose readings. 

Practical Recommendations for Veterinary Practice 

• Use serum fructosamine (SF) for short-term monitoring: SF reflects average blood glucose over 1–2 weeks and responds rapidly to insulin therapy, making it ideal for assessing recent treatment adjustments and clarifying discrepancies between clinical signs and blood glucose levels². 

• Use HbA1c for long-term monitoring: HbA1c reflects average glucose over 2–3 months and provides insight into overall glycemic control, helping evaluate the effectiveness of long-term diabetes management^1,3. 

• Consider both markers together: When comorbidities or pathological conditions may affect one marker, measuring both SF and HbA1c provides a more complete assessment of glycemic control, ensuring more accurate clinical interpretation³. 

• Interpret correlations carefully: A lack of correlation between SF and HbA1c in normoglycemic dogs does not necessarily indicate poor control but may reflect variations in protein levels³. 

Conclusion 

For veterinarians managing diabetic dogs, understanding the strengths and limitations of serum fructosamine and HbA1c is crucial for informed decision-making. While SF provides rapid feedback for insulin adjustments, HbA1c offers a long-term view of glycemic trends. Using these markers together allows for a more comprehensive approach to monitoring canine diabetes, ensuring optimal treatment outcomes and improved quality of life for diabetic dogs. 

References 

1. Norris, O. & Schermerhorn, T. (2022). Relationship between HbA1c, fructosamine and clinical assessment of glycemic control in dogs. PLoS One, 17(2), e0264275. 

2. Del Baldo, F., Magna, L., Dondi, F., Maramieri, P., Catrina, O.M., Corradini, S., Linari, G., Golinelli, S., Tardo, A.M., Bonfanti, U., Fracassi, F. (2020). Comparison of serum fructosamine and glycated hemoglobin values for assessment of glycemic control in dogs with diabetes mellitus. American Journal of Veterinary Research, 81(3), 233–242. 
3. Oikonomidis, I.L., Tsouloufi, T.K., Tzenetidou, Z., Ceron, J.J., Tvarijonaviciute, A., Konstantinidis, A.O., Soubasis, N. (2023). Diagnostic performance of glycated haemoglobin (HbA1c) for diabetes mellitus in dogs. The Veterinary Journal, 294, 105958.