Discovering the reasons underlying difficult-to-control diabetes in cats - Veterinary Medicine
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Discovering the reasons underlying difficult-to-control diabetes in cats
In the first of a two-part series, an internist reviews the insulin-related, client-related, and patient-related problems that can make a diabetes management regimen ineffective. Here is a step-by-step approach to identifying and addressing problems that underlie cases of poor diabetic regulation in cats.


Patient-related problems

There are various ways to monitor diabetic cats. If patients are doing well (that is, they are maintaining optimal body weight with minimal polyuria and no signs of hypoglycemia), measuring serum fructosamine concentrations is an excellent monitoring tool. However, correctly identifying patient-related problems generally requires frequent blood glucose measurements. Serum fructosamine concentrations or urine glucose tests do not provide enough information to reliably identify problems and guide insulin therapy in problem diabetics. Measuring blood glucose concentrations in cats poses some challenges, as many feline patients experience substantial stress-related hyperglycemia. Consequently, blood glucose measurements made in a clinic setting may be a poor reflection of glycemic events at home. In addition, many cats have substantial day-to-day variability in blood glucose measurement—in any environment.1 As at-home monitoring facilitates the collection of more data points, a more reliable picture may be generated. It is for these reasons that many practitioners are now moving away from in-clinic glucose curves on cats.

Instead, clients are taught how to obtain samples from their cats at home. The modern handheld glucometers are easy to use, and many appear to be reliable.2 They require only a tiny drop of blood, which can be collected with a lancet or needle from the ear or foot. In addition, studies have confirmed that capillary blood glucose readings are clinically comparable to results from venous sampling.3

Continuous blood glucose monitors may be a useful tool for monitoring hospitalized cats, but the measurements may also be affected by stress hyperglycemia.4 Because the receiver unit needs to stay within a few feet of the cat, using this device in the home may be difficult.

Table 1. Common Patient-Related Causes of Poor Diabetic Control in Cats.
It is helpful to categorize patient-related problems into those suggesting poor regulation (i.e. substantial fluctuations in blood glucose concentrations or episodes of hypoglycemia) or insulin resistance (i.e. excessive amounts of insulin are needed to impact blood glucose concentrations) (Table 1).

Poor regulation. Poorly regulated patients require frequent adjustments to their insulin dose or experience episodes of clinical hypoglycemia or dramatic changes in blood glucose concentrations during the day. In most cases, problems with energy (either utilization or intake) or the biological behavior of the insulin are the cause. However, an additional consideration in feline patients is the onset of diabetic remission.5,6 This commonly occurs in newly diagnosed diabetic cats; failure to identify the onset of remission may result in life-threatening insulin overdose. This possibility should always be considered in a hypoglycemic cat, particularly within the first three months of diagnosis. Careful blood glucose monitoring is needed to identify this event and to permit safe tapering of the insulin dose.

Compared with canine patients, problems with unexpected energy utilization are uncommon because cats are inherently sedentary. However, I have observed hypoglycemic collapse in a well-regulated diabetic cat after an energetic play session with a visiting child.

Similarly, a change in energy intake due to the feeding of snacks or treats is rarely an issue with our feline diabetics. However, a sudden change in diet type (such as a switch to a high-carbohydrate food) may result in poor glycemic control. Careful questioning of clients about compliance with dietary recommendations is certainly appropriate.

Problems with insulin absorption should be considered if the insulin has an erratic effect, particularly if the onset of action seems to vary from day to day. This may be due to tissue irritation at the injection site, in which case rotating through six to eight locations may solve the problem. The other consideration is the insulin type. PZI products have an innately lower bioavailability than other types, with less predictable glycemic results.7


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